:: Fincas de Ambato :: Polinización de la Jojoba en Catamarca / Análisis de Información Disponible

The 15-day irrigation delay as compared to the previous year caused an equally long lag in jojoba bud opening. Given that, in both years, the period during which female jojoba flowers stopped opening ended in late September, the period was 1/3 shorter. Based on this fact and assuming normal distribution of flower opening, Figure 1-PC illustrates the flower curve for each year under analysis.

In comparative terms, as the 2002 flower period lasted 45 days, it was 15 days longer than in 2003. This necessarily caused a higher per-day opening rate, thus dangerously increasing the damage rate during reproduction due to the potential occurrence of weather phenomena Figure 1-PC.

figuar_1pc

Adverse climatological influence was valued based on daily maximum extreme temperatures and maximum sustainable wind speed.

The analysis was based on maximum sustainable (or sustained) wind speed, instead of maximum wind gusts. A combination of the per-day wind speed figures and flower opening rates shows that, in 2003, 27% of flowers opened on days with wind speeds above 30 km/hour, whereas in 2002 this was true for 9% only (Figure 2-PC). If flower opening for days with wind speeds above 25 km/hour are factored in, 43% opened in 2003 and 30% in 2002.

figura_2pc

For several species, the steep falls in the number of pollinated flowers are associated to the presence of hot, strong winds during the flowering stage (as in the case under analysis). Some of the adverse factors involved include stigma drying-up, the increased level of pollen incompatibility, the travel speed of pollen grains preventing pollination and the excessive shaking of flowers. Ayerza y Coates (2003) reported this serious interference for this very ecosystem on olive crop experiments.

Furthermore, strong winds generate wind-blown bare soil particles, particularly in highly desertified ecosystems as is the case with the Arid Chaco area (Ayerza, 1992), creating dust storms that cause a dense dust layer to settle on the entire plant, drastically reducing the viability of available pollen (Vaknin et al., 2003).

Strong winds might also explain why virtually all of 2003’s fruit yields are due to pollination processes taking place over the first half of the reproduction period, as in this first stage the average sustainable wind speed was only 19.8 km/hour, as compared to the 27.7 km/hour average for the second half of the flowering period.

High temperatures during the pollination period have proved to be extremely adverse for several species, affecting flowering, pollination and fruit setting. A combination of the daily flowering rates and maximum temperatures (Figure 3-PC) , shows that in 2003, 72% of flower openings took place on days with temperatures exceeding 27°C, as compared to the 51% for days of equal temperatures in 2002. On days with temperatures above 32°C, the opening rate was 30% and 17% for 2003 and 2002, respectively.

figura_3pc

However, an analysis of the flower opening rates for days with temperatures best suiting pollination (< 27°C) shows that the opening rate was 49% in 2002 but only 27% in 2003.

A combination of the data provided in Figures 2-PC y 3-PC, considering only temperatures and winds above 32°C and 30 km/hour, respectively, shows that in 2003, 43% of flowers opened on days featuring at least one of these negative factors for pollination. However, in 2002, only 23% of flower openings were subject to at least one of these weather conditions.

Application of this data combination for a comparison between both halves of the normal distribution curve for 2003 shows that, in the upward part of the curve, at least one of these adverse weather factors affected 10.7 % of female flower openings, whereas the rate increases to 32% for the downward half. Such notorious difference was undoubtedly related to the virtually nil fruit yield level in the second half of the female flower opening period and the early ending of pollen release by male flowers.

On the other hand, a comparison of pollen collected for the artificial pollination program shows that pollen collected from the 2003 flowering was almost 3 times lower than that for 2002. Pollen quality was lower as well, with maximum viability at 16 and 9.84 viable grains of pollen per gram for the 2002 and 2003 collections, respectively (Coates et al., 2004).