Abstract

Argan [Argania spinosa (L.) Skeels] a multipurpose perennial tree endemic to south-west Morocco, grows in a wide array of arid to semi-arid environments characterized by great fluctuation in rainfall. As reported in other species, the reproductive phase is most vulnerable to temperature variations, but information on the effects of temperature and relative humidity on argan pollen germination are (is) still lacking. With the aim to fill this gap, in this work, the effect of temperature and relative humidity (RH) was evaluated in vitro at different combinations during two periods. Temperature, relative humidity and exposure time affect significantly the number of pollen grains germinated in vitro. We found a tendency to decrease for pollen germination following the low values of Temperature (10 °C) and / or relative humidity (15% and 50%). The best performance was observed at 25 °C and 90% of RH since percentage of pollen germination reached to 86.6% in some genotypes. But, the increasing of temperature, particularly 35 °C and 40 °C, had demonstrated inhibitory effects on pollen germination. In addition, among tested genotypes, even at 90% of RH, the average percentage of pollen germination decreased from 57.3% at 30 °C to 16.7% at 35 ° C and at a very low value of 0.53% at 40 °C. In argan forest, within-population variation in abiotic resource availability and in weather conditions was the rule rather than the exception. The selection of the most tolerant genotypes to natural weather conditions, especially in spring, was necessary for the within-population gene flow and the success of controlled crossings.