Thermal Inversion and its Relationship with Jojoba Cultivation in the Ecotone between the Arid Chaco and the Mountain Chaco, Argentina

Inversión Térmica y su Relación con el Cultivo de Jojoba en el Ecotono entre el Chaco Árido y el Chaco Serrano, Argentina

Ricardo Ayerza

The University of Arizona, Tucson, Arizona 85706, U.S.A. - Universidad Regional Amazónica IKIAM, Tena, Ecuador. rayerza@newcrops.org

Abstract

Jojoba plants were tested for three years. They were planted in three plots in the western hillside of the Sierra de Pocho, Córdoba, Argentina. The EC-El Cerro, JI-Jardín de Introducción and LQ-La Quebrada plots were located at 360, 400 and 550 masl. respectively. Minimum extreme temperatures were -1,

-3 and -6 °C for LQ, JI and EC, respectively. EC plants died in the first year due to low temperatures. Altitude and extreme minimum temperatures of May, June, July and August had a significantly high positive correlation (0.733; P<0.05). The production of LQ was significantly (P<0.05) higher than that of JI with 759 and 401 g/plant respectively. The seed weight of JI was significantly (P<0.05) higher than that of LQ with 0.85 and 0.76 g/seed respectively. Wax content was 51.4% (JI) and 51.1% (LQ). The wax content of LQ seeds varied significantly (P<0.05) between 40.6 and 55%. The presence of the atmospheric phenomenon of autumn-winter thermal inversion in the Sierra de Pocho foothills was determined as the factor of the persistence and production of jojoba.

Keywords: Seeds; Simmondsia chinensis; Temperature; Wax.

Resumen

Se testearon plantas de jojoba durante tres años. Fueron sembrados en tres parcelas en la ladera occidental de la Sierra de Pocho, Córdoba, Argentina. Las parcelas EC-El Cerro, JI-Jardín de Introducción y LQ- La Quebrada se ubicaron a 360, 400 y 550 msnm respectivamente. Las temperaturas mínimas extremas fueron -1, -3 y -6 °C para LQ, JI y EC, respectivamente. Las plantas de EC murieron el primer año debido a las bajas temperaturas. La altitud y las temperaturas mínimas extremas de mayo, junio, julio y agosto tuvieron una correlación positiva significativamente alta (0,733; P<0,05). La producción de LQ fue significativamente (P<0,05) mayor que la de JI con 759 y 401 g/planta respectivamente. El peso de la semilla de JI fue significativamente (P<0,05) mayor que el de LQ con 0,85 y 0,76 g/semilla respectivamente. El contenido de cera fue de 51,4% (JI) y 51,1% (LQ). El contenido de cera de las semillas LQ varió significativamente (P<0,05) entre 40,6 y 55%. Se determinó que la presencia del fenómeno atmosférico de inversión térmica otoñal-invernal en las estribaciones de la Sierra de Pocho era el factor de la persistencia y producción de jojoba.

Palabras clave: Cera; Simmondsia chinensis; Semillas; Temperaturas.

Ayerza R. (2026). Thermal Inversion and its Relationship with Jojoba Cultivation in the Ecotone Between the Arid Chaco and the Mountain Chaco, Argentina. Revista Ciencias Naturales 4(1), 10-25.

Recibido: 30/12/2025          Aceptado: 31/3/2026          Publicado: 31/7/2026                                                                   Editor: Olga Martínez

INTRODUCTION

Jojoba wax, produced from the Simmondsia chinensis (Link) C.K. Schneid. plant, is a raw material for the cosmetics and precision instruments industries. Its market has grown since the second half of the last century. This led to ambitious projects of planting that failed due to the lack of adaptation outside its area of origin, viz., Brazil, Costa Rica, Madagascar, Paraguay, Sudan, etc. The lack of information about regions suitable for production and the long time it takes to obtain yields have led to discouraging its cultivation, while demand continues to grow without being able to be satisfied. Today, the jojoba market is estimated at US$130.8 million per year mainly shared between the cosmetology, pharmacy and precision instruments industries (Grand View Research, 2023). In 2022, 18,211 tons of wax were sold and a growth of 6.6% is expected between 2023 and 2028 (IMARC

Group, 2023).

The jojoba crop was introduced in Argentina in 1976 at El Desafío farm located in the Sierra de Pocho foothills, Córdoba. The place is an ecotone between the Mountain Chaco and the Arid Chaco (Ayerza, 1990a).

Today, Argentina has 2,455 commercial hectares, concentrated in the Arauco Depart- ment, La Rioja Province (Ayerza, 2020a; N. Vinelli, Aimogasta, La Rioja, personal com- munication 2025). However, it reached 13,000 hectares with commercial expectations, most of which they never produced due to the lack of adaptation of the species to the selected places (Coates & Ayerza, 2008). Planting si- tes included Capital Department (La Rioja), Valle de Catamarca (Catamarca) and Las Col- menas (Salta). Experimental plots were also established in Fuerte Esperanza (Chaco), Ing. Juárez (Formosa), San Martín (Mendoza) and Burruyacú (Tucumán).

This lack of adaptation was essentially due to thermal conditions. The minimum temperatures in areas such as San Martín, Mendoza (Monte Desert) and Department Capital, La Rioja (Arid Chaco) eliminated the flowers and even killed the young plants. In the Semiarid Chaco such as Tucumán, Salta and Formosa, the lack of enough winter cold did not allow the vernalization phenomenon thus inhibiting the beginning of the floral opening period (Ayerza, 1990a, 1992).

Between 2013 and 2017, Argentina was the main jojoba producer in the world. It was then displaced to third place by Israel and Peru due to increased yields and increased planted areas in both countries. The determination of new areas suitable for the crop, together with the availability of higher production clones could allow the country to retrieve positions in the market.

The Since 1990, the production area has remained constant (N. Vinelli, Aimogasta, La Rioja, personal communication, 2025). This area in the Arauco Department, La Rioja Province, could extend to the west, ascending on the foothill of the Sierra de Velazco, taking advantage of the winter thermal inversion phenomenon. There, the increased production of jojoba plants as altitude increases has been determined. In the center of the valley, the extreme minimum temperatures can reach

-9°C (Ayerza, 1990a).

In these regions, the low rainfall (100 to 150 mm/year) on the slopes suitable for cultivation is an important limitation, so it is essential to resort to irrigation. The water tables are 200 m deep, with flows of 150 to 200 m3/hour. To obtain higher flows and structural stability of the perforations it is necessary to reach 400 to 440 m deep. This implies very important infrastructure and pumping costs that put at risk the economic results of the plantations (Tálamo et al., 2013).

On the other hand, the decrease in water resources is forcing the world to pay attention to the use of water. The decrease in groundwater and its flows due to the overexploitation of aquifers, as well as the destruction of vegetation and tree cover that exacerbates soil erosion and reduces groundwater recharge, increases water scarcity and food insecurity (United Nations, 2019).

A basic factor for expanding jojoba cultivation in the country and ensuring sustainability is to find thermally suitable areas for cultivation with adequate rainfall regimes, using irrigation only as strategic support.

Based on the recent determination of the thermal inversion phenomenon in the Sierras de Pocho, Córdoba, Argentina (Ayerza, 2023), this paper is aimed to define its relationship with the productive jojoba behavior in the said ecosystem and under rainfed conditions. Even though the presented data were obtained between 1980 and 1986, the conclusions of the study were never published. Knowing the behavior of the species and the essential edaphoclimatic characteristics of the region, would allow adding an area to establish more sustainable commercial jojoba projects than the current ones, by not having to resort to irrigation.

MATERIALS AND METHODS

The work was carried out at El Desafío farm, located on the western slope of the Pocho Mountain, Pocho, Córdoba, Argentina. The place belongs to the so-called Eastern Pampa Mountains.

Seeds to be planted were harvested in July 1980, from a hillside exposed to the north of the Tucson Mountains, Tucson, Arizona (32°14’13” N and 111°02’55” W) between

778 and 810 masl, with a slope of 25.6%. Plants density was 0.21 plants/m2 with a male- to-female ratio of 46.55% of male plants and 51.72% of female plants, which suggests a significant variability in the seed’s genetic composition (Ayerza, 2025).

Seeds from 10 plants selected at random two years earlier were harvested (Tables 3 and 4). These plants had been identified and monitored and their annual fruiting was observed (Ayerza, 1984). Later on, between 1981 and 1984, the floral biology of this jojoba stand was studied confirming a significant variability among individuals (Buchmann, 1987).

Winter thermal inversion phenomenon was determined in the Tucson Mountains hillsides where the native jojoba plants grow (Shreve, 1912; U.S. Army Corps of Engineers, 1997). This explains this species’ presence on the hillside as well as their absence in the center of the valleys (Ayerza, 1990a).

The seeds were brought to Argentina where three random samples were taken after mixing them. In October 1980, three plots were planted in a western hillside of the Sierra de Pocho, in an ecotone between the Arid Chaco and the Mountain Chaco, at 31°64’ south latitude. The EC (El Cerro) plot was located at 360, the JI (Jardín de Introducción) plot was located at 400 masl and LQ (La Quebrada) plot was located at 550 masl.

The distance between LQ and JI was 2,404 m and between JI and EC, 1,649 m. The slope percentage was 4.16 and 2.43 for LQ and JI respectively. The description of the measurement instruments placed in each site for the collection of temperature and rainfall data for the period 1983-1986 were described by Ayerza (2023).

To determine possible differences between the soils of the plots, a chemical analysis of composite samples from each plot, taken in the first 40 cm of depth, was carried out. The method used was Mehlich 3 (Mehlich, 1984) for calcium, magnesium, potassium and sodium; that of Bray & Kurtz (1945) for phosphorus; that of Kjeldahl for nitrogen (Chapman & Pratt, 1961) and that of Walkley- Black for organic matter and carbon (Walkley

& Black, 1934). The pH was determined by

electrometric method (Bates, 1973).

The planting framework was one seed per meter in the row, and four meters apart between them. The seeds were soaked for 48 hours before planting and only those that were swollen were planted. The plots were irrigated by furrow only during the first month and no fertilizer were applied during the analyzed years. When the plants were three years old, 43 female plants were randomly selected in LQ and 22 in JI, being 50% of the total female plants of each plot. The selected plants were within the rows, discarding the edges with a male-to-female ratio being 1:1 in each plot. In the EC plots no plants were chosen since they disappeared before they were three years old due to the extremely low temperatures.

Every year, between November and January, the seeds were manually collected. The followingApril, they were cleaned, dried in the shade and weighed. In all cases, the weight had 4% moisture, using for its determination a Delver HD-1021 meter (Delver S.A., La Plata, Buenos Aires, Argentina).

The seeds were stored at room temperature until 1988, when the liquid wax content was determined. Seeds from seven plants were taken at random from the QL site and since after the physical determinations the JI seeds were mixed, two composite samples (JI and JI) were taken for analysis. The determination was done through the AOCS Ac-3-44 (AOCS, 1984) method at the laboratory of Jojoba Growers and Processors Inc., Apache Junction, Arizona, US.

The information collected in this experiment was analyzed in 2022. The statistical determinations (Standard Deviation, Multiple Comparison of Means and Correlations) were carried out using the CoStat software (CoHort Stat, 2006).

I was not used in the preparation of this paper.

RESULTS AND DISCUSSION

Table 1 shows the soils chemical composition of the EC, JI and LQ plots and Tucson hillside where the plants from which the original seeds were collected.

The soils of the three trial plots were chemically very similar to each other, being typical of the region (Hang et al., 1995; Bocco et al., 2007; Karlin, 2013). Therefore, an influence of this factor between the implanted sites was ruled out. All the values obtained were within the limits of the Sonora Desert and Californian Mediterranean soils, where the native jojoba stands are located (Ayerza, 2025). However, the Tucson soil presented a lower pH, a lower organic matter content, a lower calcium content and more phosphorus than the soils of the trial. The data of the soils in which the jojoba crop is successfully developed show that the differences between the Tucson soils and those of the trial are not sufficient to interfere in their development (Gentry, 1958; Brooks, 1978; Ayerza, 1990a).

Table 2 shows the extreme temperatures recorded during the studied years. The plants from the EC plot were strongly affected by low temperatures, most of them dying at temperatures of -6°C. The remaining plants died between 1984 and 1985 with temperatures of up to -5 and -6°C without any producing, so the EC plot had to be left aside. Although adult jojoba plants can survive extreme minimum temperatures of -9.5°C, young plants die with

Site	pH	C	MO %	N	Ca	Mg	K mg/100 g of soil	Na	P	C/N ratio
LQ	7.6	1.05	2.10	0.099	370	30	89	3	0.8	10.6
JI	7.6	1.10	2.20	0.093	380	60	87	3	1.08	11.8
EC	7.8	1.25	2.50	0.096	290	36	89	3	0.96	13.1
Mean	7.7	1.1	2.3	0.1	346.7	42.0	88.3	3	0.9	11.8
SD1	0.12	0.10	0.21	0.00	49.33	15.87	1.15	0.00	0.14	1.25
Tucson2	6.6	0.45	0.90	0.051	160	48	16	3	5.76	8.8

1 Standard Deviation; 2 hillsides where the original seeds were collected.

Table 1. Soils chemical composition of the EC, JI, LQ plots in the Sierra de Pocho foot hills, Córdoba, Argentina

Month	J	F	M	A	M	J	J	A	S	O	N	D	SD	Mean
Absolute minimum temperature(°C)
LQ-83	12.70	15	12	13	-1	-1	1	4	3	7	12	16	6.36	7.81
LQ-84	18	13	12	7	1	1	1	1	4	6	10	7	5.59	6.75
LQ-85	10	14	8	6	5	1	-1	-1	4	6	10	10	4.71	6.00
SD1	4.07	1	2.31	3.79	3.06	1.15	1.15	2.52	0.58	0.58	1.15	4.58	-	-
Mean	13.60	14	10.70	8.70	1.70	0.30	0.30	1.30	3.70	6.30	10.70	11	5.60	6.90
JI-83	19	17	12	13	-3	-3	0	3	0	6	12	16	8.09	7.67
JI-84	13	17	10	5	-1	2	3	-3	4	9	7	11	5.87	6.42
JI-85	8	10	7	0	3	-2	-2	0	3	6	11	12	5.03	4.67
SD	5.51	4.04	2.52	6.56	3.06	2.65	2.52	3.00	2.08	1.73	2.65	2.65	-	-
Mean	13.33	14.67	9.67	6	-0.33	-1	0.33	0.00	2.33	7	10	13	6.33	6.25
EC-83	16	16	12	2	-4	-6	0	2	0	4	14	18	8.50	6.17
EC-84	19	18	10	4	-5	-3	-4	-5	4	7	7	9	8.32	5.08
EC-85	10	9	7	-3	-3	-6	-5	-4.5	0	7	10	11	6.82	2.71
SD	4.58	4.73	2.52	3.61	1	1.73	2.65	3.91	2.31	1.73	3.51	4.73	-	-
Mean	15	14.30	9.70	1	-4	-5	-3	-2.50	1.30	6	10.30	12.70	7.90	4.70
1 Standard Deviation

Table 2. Absolute minimum temperature by site and year.

extreme minimum temperatures between -4 and -5°C (Gentry,1958; Yermanos, 1982; Nelson & Palzkill, 1993). In addition to the differences in the extreme minimum temperatures of the studied period, there were also differences in the number of months with frosts, being 11, 6 and 4 for EC, JI and LQ, respectively (Table 2).

The Fig. 1 shows the curves of the mean extreme minimum, mean extreme maximum and mean annual temperatures for the period 1983-1985 at the three surveyed sites. This graph allows us to observe the presence of the atmospheric phenomenon of thermal inversion during autumn-winter (May, June, July and August), responsible for the increase in extreme minimum temperatures as altitude increases, as reported for the 1983-1986 period (Ayerza, 2023).

This same behavior regarding altitude and minimum winter temperatures was determined in the northern Sonoran Desert, on a slope with native jojoba in Cave Creek, Arizona, USA, between the base 610 masl and 730 masl (Burden, 1970).

The extreme minimum temperatures of May, June, July and August (Fig. 2) and the altitude between 360 and 550 masl, presented a significantly high positive correlation (0.733; P<0.05).

Figure 1. Correlation of the extreme minimum temperature of May, June, July and August versus altitude.

Figure 2. Extreme minimum, extreme maximum and annual mean temperatures for the period 1983-1985 at the three surveyed sites.

According to Ayerza (2004), the jojoba flowering period in the ecotone between the Mountain Chaco and the Arid Chaco forms a Gaussian curve that begins in mid-June and lasts until mid-September, coinciding this extension of the floral period with that of the original population (Buchmann, 1987). This long flowering period is made up of two essential aspects: variability of the flowering beginning of the different genotypes and extended opening period in the same plant. It has been shown that the beginning of flowering depends on the vernalization requirement of each genotype (Ferriere et al., 1989; Benzioni et al., 1992; Dunstone, 1995; Milthorpe, 2006), as well as the length of the opening period (Dunstone, 1980; Nerd & Benzioni, 1988), and in both cases of their interactions with climatic conditions.

In the foothills of the Sierra de Ancasti, Catamarca, Argentina, an ecotone between the Mountain Chaco and the Arid Chaco, the individual flowering period has been determined between 20 and 46 days to reach 90% of floral opening, depending on the genotype and weather conditions (Ayerza, 2004). Although the same clone controlled in this foothill for two consecutive years, presented a similar flowering period of 27 days, between August 20 and September 17, and 24 days, between September 8 and October 2, the following year, the start date presented a difference of 19 days (Coates & Ayerza, 2008). The variation between years in the beginning and length of flowering has been determined in other jojoba populations with similar values (Nahla et al., 2018; Perry et al., 2021).

Since freezing in plants is a progressive process, the duration of freezing temperatures is a decisive factor (Díaz-Queralto, 1971; Livingston, 2018; Bravo et al., 2020). The frequency variability of wild jojoba plants is influenced by changes in slope angle (Burden, 1970); the steeper the slope, the shorter the duration of the frost (Snyder & Melo- Abreu, 2005).

In the northern Sonoran Desert, in the mountains of Cave Creek, Arizona, a highly significant positive correlation (R = 0.524; P<0.01) was demonstrated between the presence of this plant and the slope angle. Its degree is closely linked, not only with the circulation of the air, but also with its speed and, therefore, with the duration of the low temperatures (Burden, 1970).

The slope in LQ was 4.16% while in JI it was 2.43%, so the duration of the low temperatures must necessarily have been shorter in LQ than in JI, which must also have influenced the differences between the plant yields of both sites. Tables 4 and 5 show the individual weights of the seeds and the yields per plant of the LQ and JI sites during the three years studied.

Plant	Weight (g/seed)				Yield (g/plant)
	1983	1984	1985	Media	1983	1984	1985	Total
Q P 7  11	0.79	0.92	0.73	0.81	4.0	272.0	115.4	391.3
Q P 7  12	0.77	0.88	0.71	0.79	4.6	268.4	206.6	479.6
Q P 4  4	0.89	0.83	0.71	0.81	7.1	243.2	117.9	368.3
Q P 6  9	0.48	0.75	0.76	0.66	6.8	290.0	241.5	538.3
Q P 4  8	0.79	0.89	0.62	0.77	346.0	644.5	814.7	1,805.2
Q P 4  3	0.63	0.85	0.68	0.72	23.4	349.3	1,087.1	1,459.8
Q P 7  2	0.89	0.87	0.69	0.82	8.0	226.8	198.7	433.5
Q P 9  9	0.93	0.90	1.01	0.95	10.2	266.0	307.9	584.1
Q P 6  10	0.58	0.88	0.78	0.75	27.8	442.0	1,088.3	1,558.1
Q P 5  15	0.22	0.88	0.67	0.59	35.7	464.3	1,140.3	1,640.3
Q P 4  1	0.63	0.78	0.70	0.70	6.9	170.0	150.4	327.3
Q P 3  2	0.59	0.88	0.74	0.74	31.7	208.0	1,284.2	1,523.9
Q P 4  16	0.72	0.68	0.53	0.64	22.9	324.6	518.7	866.3
Q P 11 12	0.63	0.86	0.72	0.74	24.5	212.6	834.9	1,072.0
Q P 4  2	0.60	0.83	0.65	0.69	22.1	359.2	283.4	664.8
Q P 5  17	1.12	0.88	0.88	0.96	17.9	390.6	223.5	632.1
Q P 9  7	0.56	0.91	0.67	0.71	15.7	234.0	371.0	620.6
Q P 8  3	0.59	0.85	0.73	0.72	8.3	155.3	142.7	306.2
Q P 4  10	0.96	0.74	0.60	0.77	67.1	534.0	560.7	1,161.8
Q P 6  13	0.68	0.88	0.66	0.74	56.1	492.8	570.3	1,119.3
Q P 5  8	0.62	1.01	0.67	0.77	99.2	290.0	1029.7	1,418.9
Q P 3  10	0.46	0.82	0.56	0.61	41.8	315.5	525.2	882.5
Q P 3  14	0.77	0.84	0.82	0.81	81.6	319.6	186.7	587.9
Q P 3  8	0.64	0.84	0.66	0.71	44.1	351.9	469.4	865.4
Q P 11  9	0.86	0.86	0.70	0.81	18.9	184.0	477.8	680.7
Q P 5  5	0.58	0.88	0.66	0.71	23.2	242.2	415.3	680.7
Q P 3  13	0.61	0.80	0.84	0.75	7.9	138.9	274.8	421.6
Q P 3  3	0.77	0.77	0.70	0.75	17.0	221.9	372.8	611.7
Q P 3  7	0.59	0.78	0.67	0.68	300.2	559.6	556.7	1,416.5
Q P 5  18	0.82	0.87	0.86	0.85	58.9	299.1	656.0	1,014.0
Q P 5  16	0.77	0.85	0.64	0.75	11.5	176.9	292.9	481.3
Q P 3  5	0.77	0.87	0.70	0.78	138.0	288.6	776.4	1,203.0
Q P 3  6	0.60	0.79	0.73	0.71	15.1	163.6	390.9	569.6
Q 1	0.52	0.67	0.75	0.65	25.4	76.0	420.5	521.9
Q P 3  20	0.74	0.89	0.70	0.78	24.5	247.5	166.9	438.9
Q P 5  12	0.79	0.87	0.84	0.83	25.4	214.4	224.0	463.8
Q P 1  6	0.85	0.93	0.96	0.91	27.2	187.7	299.3	514.2
Q P 3  17	0.78	0.85	0.74	0.79	28.9	242.0	182.0	452.9
Q P 4  17	0.63	0.64	0.62	0.63	19.6	163.1	142.2	324.8
Q P 2  5	0.90	0.80	0.71	0.80	55.5	177.2	183.4	416.1
Q P 2  10	0.71	0.87	0.90	0.83	32.8	163.6	326.9	523.3
Q 3	0.57	0.67	0.68	0.64	18.3	91.5	220.6	330.5
Q P 1  2	0.77	0.94	0.97	0.89	13.1	76.1	156.9	246.2
Mean	0.70	0.84	0.73	0.76	43.60	272.99	441.99	758.59
SD1	0.16	0.08	0.10	0.084	68.10	127.88	314.65	426.18
1 Standard Deviation

Table 3. Seeds weight and yield of plants from LQ site.

Table 3 shows that 30.1% of the LQ plants reduced their production between 1984 and 1985, compared to only one (5%) in the JI (Table 4). In this last site, the J P plant was

the only one between both sites that reduced its production between 1983 and 1984. Works have been reported in which many jojoba genotypes present the characteristic called alternation, which implies productive alternation, which in many cases becomes very pronounced both in commercial plantations and in native plants (Yermanos

& Duncan, 1976; Yermanos, 1982; Perry et al., 2021). This phenomenon is common in other crops such as olive (Olea europaea L.), juniper (Juniperus thurifera L.), pecan (Carya illinoensis [Wangenh] K. Koch) and various fruit trees. (Medina-Morales et al., 2000; Ramírez-Santa Paul, 2001; Montesinos-Torres, 2007).

The alternating or biennial production is a widely distributed phenomenon that is repeated in the different production areas and the metabolic processes and their induction are still only partially known. (Lavee, 2007; Kour et al., 2018; Wünsche, 2021). It has recently been shown in jojoba that, depending on the genotype and the type of pruning applied, the alternation phenomenon can be significantly reduced (Lazare et al., 2021).

However, Table 3 shows that 69.8% of the LQ plants did not present alternation, and Table 4 shows that 96% of JI plants

Plant	Weight (g/seed)				Yield (g/plant)
	1983	1984	1985	Media	1983	1984	1985	Total
J P 3  22	---	0.90	1	0.95	---	1125.1	261.2	1386.3
J P 4  5	0.74	0.86	0.99	0.86	182.3	235.8	340.8	759.0
J P 4  14	0.81	0.97	0.98	0.92	81.5	110.1	225.4	416.9
J P 3  20	0.67	0.74	0.90	0.77	15.5	140.6	263.3	419.4
J P 3  11	0.64	0.82	0.99	0.82	5.8	47.5	155.7	209.0
J P 3  1	0.83	0.86	0.70	0.80	59.7	197.3	273.7	530.7
J P 3  8	0.77	0.94	1.01	0.91	50.8	111.8	258.5	421.1
J P 2  9	0.88	0.93	0.99	0.93	49.3	69.0	161.6	279.9
J P 3  5	0.65	0.74	0.77	0.72	21.5	117.7	239.7	378.9
J P 2  8	0.85	0.95	0.92	0.91	113.3	206.8	320.7	640.8
J P 4  2	0.69	0.77	1.01	0.82	22.0	75.5	145.0	242.5
J P 4  21	0.58	0.92	0.97	0.82	12.2	96.9	183.9	293.0
J P 4  6	0.78	0.94	0.91	0.88	110.8	211.7	297.6	620.1
J P 4  14	0.81	0.82	1.00	0.88	10.5	59.1	137.0	206.7
J P 3  16	0.93	0.75	1.00	0.89	14.8	67.7	150.4	232.9
J P 2  10	0.88	0.82	0.85	0.85	33.5	69.2	143.0	245.7
J P 4  7	1.05	0.54	0.98	0.86	45.3	40.6	184.3	270.3
J P 4  20	0.86	0.93	0.79	0.86	30.1	80.8	173.9	284.8
J P 3  19	0.88	0.70	0.95	0.84	29.0	41.9	131.2	202.1
J P 3  13	0.82	0.81	0.97	0.87	27.2	75.5	155.6	258.2
J P 2  12	0.85	0.82	0.94	0.87	35.7	61.8	161.2	258.7
J P 4  3	0.54	0.62	0.93	0.70	30.3	68.0	120.4	218.6
Mean	0.79	0.83	0.93	0.85	46.72	150.47	203.82	398.89
SD	0.12	0.11	0.09	0.06	43.17	225.42	67.01	271.26
1 Standard Deviation

Table 4. Seed weight and yield of plants from the JI site

did not present this characteristic either. The presence of plants with and without alternation was identified in plantations carried out in Riverside, California, both within plots with wild seeds originating from the coast and the inland of the Californian Mediterranean ecosystem (Yermanos, 1982), in Mesa, Arizona, with seeds from wild plants originating in Arizona, California and Baja California, and in cultivated plants from Israel; 90% of plants showed productive alternation (Palzkill & Hogan, 1982). In Hermosillo, Sonora, Mexico, 210 plants were studied for four years, determining 49.7% of plants with alternate production (Durazo, 1982). The alternate production regarding the number of inflorescences has also been reported in male jojoba plants (Tel-Zur et al., 2020).

With the information available here, it is not possible to determine the reasons for the differences in the percentages of alternation between the LQ and JI plants, but it could be related to the interactions between genetics and the environment, especially with the differences in extreme minimum temperatures between both sites (Table 2). From the genetic point of view, it should be kept in mind that the 10 plants from which the original seeds were collected had annual production determined, but since these were not measured, we do not know if they were productions with or without annual ups and downs. It should be added that jojoba has separate sexes and in the same plant the different seeds can have different male parents, making up a high genetic variability between the used seeds.

The values of the standard deviation of the total produced in the tested period (Tables 3 and 4) show a greater dispersion of the yields among the LQ plants than among the JI ones. The extreme minimum temperatures when damaging flowers, both closed at -3°C and open at -1°C, prevent expressing the productive potential of many genotypes (eg. the occurrence of -1°C in early flower openings), standardizing mean production from the JI site. The standard deviation values show that for the LQ site a clonal selection process would be much more efficient than in the JI. Likewise, the reduced magnitude of the standard deviation of the plants from the JI site could indicate that these genotypes are at the limit of their adaptation zone as suggested by Ayerza & Zeaser (1986).

Table 5 shows that despite the high percentage of biennial plants in the LQ plot, the production per area unit increased every year. This characteristic of a high number of alternations, but with an annual increase in total production per area unit, was previously reported in experimental and commercial plantations in Mesa, Arizona, US, and in Bakersfield, California, US (Palzkill & Hogan, 1982). The annual increase in the production of the non-alternation plants compensated the decrease of the alternation plants, in the yields per area unit.

Table 5 shows that the mean production of both sites increased significantly (P<0.05) with age, except for the JI site between 1984 and 1985 which, although numerically increased, the difference was not statistically significant (P<0.05). These annual yields increase is the usual result for numerous species and within them among genotypes that do not present the phenomenon of alternation; in developing

	Site	1983	1984 g/plant	1985	LSD2	Total g/plant
	LQ	43.6ª.C.1	272.2ª.B	441.9ª.A	85.40	758.6ª
	JI	46.7ª.B	150.5b.A	203.3b.A	85.78	400.5b
1	differentlo	wercase letters in	the same column	(t Student test) and	uppercase letter	in the same

row (Student-Newman-Keuls test), are significantly (P<0.05) different;2 least significant difference according to Student-Newman-Keulstest..

Table 5. Mean jojoba productions from the LQ and JI sites at 3, 4 and 5 years of age.

plants it is related to the increase of biomass volume (Jiménez-Méndez et al., 2019; Fan et al., 2020).

Undoubtedly, the LQ site was significantly (P<0.05) more productive than the JI (Table 5). Taking the yield of the LQ site to one hectare after five years means production of 995 kg/ha (2,500 plants – 10% of male plants = 2,250 female plants/ha), which is within the yields achieved at that age in commercial plantations originating from seeds in Mexico, the US and the current area of commercial production in Argentina, in the Province of La Rioja (Ayerza, 2016, 2020b).

The mean yields reached in the fifth year were higher than the mean attained in Riverside, California, USA, in plantations originating from seed and with irrigation (Ayerza, 1989). But in the third year they were lower than the media obtained from three- year-old plants from seeds in Hermosillo, Sonora, Mexico, under irrigation conditions (Ramonet & Morales, 1985).

The mean of the eight three-year-old clones implanted under irrigation conditions in the Table 5 shows that the comparative production between sites determined productions without significant difference (P<0.05) in 1983, while in 1984 and 1985 the production of the LQ plants was significantly (P<0.5) higher than those of JI. The lack of statistical significance (P<0.05) between the productions of 1983 in both sites, may be due to the presence of frosts in June and July (Table 2). Although they were lower in LQ, one degree Celsius below zero is enough to kill open flowers (Ayerza, 1990a). In 1984 and 1985, frost occurred early in JI but not in LQ, thus justifying the productive differences between sites.

Milthorpe and Dunstone (1989) found that genotypes that broke dormancy late were more likely to survive frost events. The variability in the floral opening date of the different genotypes has been demonstrated on the slope where the original seeds were collected (Buchmann, 1987).

The potential, resorting to the cloning and use of the superior genotype, in the fifth year represents productions of 2,900 kg/ha for the LQ site (Q3P2) and 767 kg/ha for the JI (J4P5). The projection of the LQ production is higher than the mean of 954 kg/ha, mean 2010-2019, and even the 1,363 kg/ha of the year 2015, which was the one with the highest mean production, of the adult Argentine commercial plantations maintained under irrigation in La Rioja (Ayerza, 2020b).

However, it is far from the maximum yields achieved in Israel (7,070 kg/ha) (Perry et al., 2021) or Aimogasta (5,000 kg/ha) (Norberto Vinelli, personal communication, Aimogasta,

La Rioja, Argentina, 2023) in adult plantations of clones with drip irrigation and fertilization.

Q4P8 and J3P22were the plants with the highest accumulated production of the analyzed three years with 1,805 g and 1,386 g/plant respectively (Tables 3 and 4). The

productive difference determined between the LQ and JI sites, considering only the production of the most productive plant in the fifth year, significantly decreased in favor of

Month	J	F	M	A	M	J	J	A	S	O	N	D	Total	SD
Rainfall (mm)
LQ-83	398	0	17	26	0	0	0	31	29	65	76	85	727	115.63
LQ-84	197	106	63	6	0	0	0	0	48	2	20	212	654	62.45
LQ-85	100	0	62	11	0	0	110	36	0	7	82	96	504	43.59
SD	151.9	61.20	26.27	10.41	0.00	0.00	63.51	19.50	24.17	35.02	34.20	70.36		37.36
Mean	231.7	35.3	47.3	14.3	0.0	0.0	36.7	22.3	25.7	24.7	59.3	131.0	628.3	73.9
JI-83	322	51	6	16	0	0	13	26	26	54	62	88	664	88.35
JI-84	189	104	59	6	0	0	0	0	44	2	25	218	647	77.02
JI-85	104	72	54	8	0	0	107	27	0	10	85	62	529	41.57
SD	109.8	26.69	29.26	5.29	0.00	0.00	58.39	15.31	22.12	28.00	30.27	83.58		24.40
Mean	205.0	75.7	39.7	10.0	0.0	0.0	40.0	17.7	23.3	22.0	57.3	122.7	613.3	69.0
EC-83	369	46	11	19	0	14	14	29	28	57	65	82	734	100.04
EC-84	190	112	52	5	0	0	0	0	44	2	21	216	642	77.50
EC-85	105	68	46	10	0	0	107	0	0	12	102	64	514	44.66
SD	134.7	33.61	22.14	7.09	0.00	8.08	58.16	16.74	22.27	29.30	40.55	83.05		27.85
Mean	221.3	75.3	36.3	11.3	0.0	4.7	40.3	9.7	24.0	23.7	62.7	120.7	630.0	74.1

Table 6. Rainfall by site and year.

LQ. Thus, production of JI went from 26% to 77% concerning LQ.

These productions were obtained without irrigation, with the annual rainfall shown in Table 6. The data show that the maximum difference in rainfall between sites occurred in 1983 with 10% in favor of the LQ site. The distribution of rainfall was typical of the Chaco region, with a hot and rainy season and a temperate and dry season. The rainfalls of June and August 1984 must be considered an anomaly in the Arid Chaco (NCEI, 2022).

The rainfalls of the three studied years agree with the mean values of the period 1970- 2011 (673 mm) in Villa Dolores, Córdoba, 30 km south of El Desafío, on the foothills of the Sierras de los Comechingones. Thus, they also agree with the mean for the period 1973- 2003 (512 mm) measured in the Chancani Forest Reserve, on the foothills of the Sierra de Pocho, 24 km north of El Desafío (Iglesias et al., 2010; Karlin, 2012).

Rainfalls measured in this work were 45% above the mean of 433 mm obtained in Superior, Arizona, in the northern limit of the Sonoran Desert, considered one of the most productive areas of native jojoba (Ayerza, 1990a).

Except the LQ weights for 1983 and 1985, the individual seed weights obtained for both sites (Table 7) were higher than those determined as the mean of the germplasm collection of the native stands of the species in their areas of origin: Sonoran Desert,

Site	1983 (g/seed)	1984	1985	LSD2	Total (g/seed)
LQ	0.70b.B.1	0.83ª.A	0.73b.B	0.05	0.76b
JI	0.79ª.B	0.82ª.B	0.93ª.A	0.07	0.85ª

1differentlowercase letters in the same column (t Student test) and uppercase letter in the same row (Student-Newman-Keuls test), are significantly (P<0.05) different; 2 least significant difference according to Student-Newman-Keuls test.

Table 7. Mean weight of the seeds produced in LQ and JI at 3, 4 and 5 years of age.

Year         1983         1984       1985       Media       SD          LSD4

Plant          (% of wax2)

Q P 3  2	52.9	53.2	51.2	52.4ab3	1.08	---
Q P 3  6	49.8	52.4	50.6	50.9ab	1.33	---
Q P 3  8	40.6	51.9	49.7	47.4b	5.99	---
Q P 3  10	49.7	52.8	49.7	50.7ab	1.79	---
Q P 4  8	55	53.5	50.8	53.1ª	2.13	---
Q P 4  10	49.7	52.8	49.7	50.7ab	1.79	---
Q P 6  10	50.9	53.4	52.3	52.2ab	1.25	---
Mean	49.8b.3	52.9ª	50.7ªb	51.1	---	3.61
SD1	4.52	0.57	0.98	1.87	---	---
LSD4	---	---	---	4.74	---	---
JI 5 1	---	---	---	51.7	---	---
JI 5 2	---	---	---	51.1	---	---
Mean	---	---	---	51.4	---	---
SD1	---	---	---	0.42	---	---

1Standard deviation;2 percentage on the dry weight of the seed; 3 different letters in the same column or row are significantly (P<0.05) different according to Student-Newman-Keuls test; 4 least significant difference; 5years and plants sample; LQ n = 3.

Table 8. Variability of wax content between years and between genotypes.

Californian Mediterranean and Los Cabos Tropical Region. This was 0.56 g (0.36 – 0.75g/plant) measured at 4% seed moisture (Ayerza,1990b). The variability of the individual seeds’ weight between years is affected by climatic conditions (Goytia- Jiménez et al., 2011), which may be the explanation for the indicated variations. The significant difference (P<0.05) between the individual weights of LQ and JI cannot be explained with the available information.

The wax content of seven plants chosen at random from the LQ site (Table 8) showed yields between 40.6% and 55%, depending on the genotype and the year. Through the

their interactions, both in jojoba and in other species, viz., moringa and olive (Dunstone et al., 1985; Ayerza, 2011, 2020b; Nissim et al., 2020), which could justify the differences measured in this work.

Open pollination and the availability of pollen from different male plants in jojoba plots also influence the variability of the wax content of the seeds from different plants of the same clone, in the same site and year. This was demonstrated in the foothills of the Sierra de Ancasti, Catamarca, Argentina (Ayerza, 2020b) and Ramat Negev, Israel (Benzioni & Vaknin, 2002).

The standard deviation magnitude of the

wax percentage of the three measured years (Table 8) shows a great dispersion between genotypes for 1983 and within each genotype through the years. The standard deviation of the Q3P8 genotype showed the highest comparative variability.

The mean annual wax production of the LQ plant seeds (Table 8) was significantly (P<0.05) higher in 1984, compared to that of 1983, and also 1985, although in the latter case

the difference was not significant (P<0.05). It has been shown that the percentage of jojoba wax increases when the fruiting process starts early (Perry et al., 2021). The year

with the highest wax content was 1984, with no frost interfering with the beginning and development of the fruiting period (Table 2).

On the other hand, the JI1 and JI2 composite samples (Table 8), with liquid wax yields of 51.70% and 51.10% were within the limits  obtained from the LQ plants.

The wax percentages obtained here agree with those reported by other authors in seeds collected from wild plants in different regions of the Sonoran Desert and the Californian Mediterranean ecosystem. Araiza-Lizarde et al. (2017) reported for seeds collected in three locations in Mexico, Sonoyta, Todos Santos and La Huerta, (49 ± 2.80), (44 ± 1.35) and (43 ±

1.00) %, respectively. Miwa (1971) determined 48.4%and 40.5% for two sites in Arizona, and for the Californian Mediterranean ecosystem, 52,5% in inland stands and 49.4% in plants located on the coast; Ayerza (1990b) in wild jojoba plants located in 8 sites in Arizona, 3 in Baja California, 4 in Baja California Sur, 3 in California and 2 in Sonora, obtained a mean of 48.9% and extremes of 45% and 53%.

Regarding their comparison with the wax decreases the extreme minimum temperatures when ascending the slope. The intensity of this effect decreased as the altitude descended, making the autumn-winter thermal regime inadequate for jojoba below 400 masl.

ACKNOWLEDGMENTS

The author acknowledges support for this project from Quitral-co SAIC, Buenos Aires, Argentina and International Flora Technologies, Chandler, Arizona, U.S.A

CONCLUSIONS

These results contribute to understanding the ecosystem conditions where jojoba was planted in Argentina, explaining its persistence 40 years later. The work surveyed the climatic conditions that allowed its planting and development in the ecotone between the Arid Chaco and the Mountain Chaco, between 550 and 400 meters above sea level, in the foothills of the Sierra de Pocho, Córdoba, whose slope allows a suitable strip 2.4 km wide.

The presence of the atmospheric phenomenon of autumn-winter thermal inversion in the Sierra de Pocho foothills was determined as the factor of the persistence and production of jojoba. This phenomenon decreases the extreme minimum temperatures when ascending the slope. The intensity of this effect decreased as the altitude descended, making the autumn-winter thermal regime inadequate for jojoba below 400 masl.

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