Eco-physiological studies on desert plants : II. Germination of Zygophyllum coccineum L. seeds under different conditions.

Zygophyllum coccineum seeds were tested for germination under different conditions. They showed ability to germinate under a wide range of temperature from 10 to 35°C. The maximum percentage of germination was 92.5, reached at 25°C in darkness.Germination at alternating temperatures was lower than at 25°C. Seeds failing to germinate at 4 and 40°C showed high rate of germination when transferred to 25°C in dark.Exposure of seeds to light during germination inhibited the rate and percentage of germination at all temperatures. The germination percentage in alternating light was higher than that in continuous light, but both were lower than the percentage in complete darkness. The radicle is longer in dark germinated seedlings than in light germinated ones.The optimal depth of sowing was found to be 1 cm. Such a depth has numerous advantages for the germinating seeds. These advantages include the protection of the seeds against the inhibitory effect of light and against the rapid desiccation of the superficial soil layer.The seeds were able to germinate under high moisture stress in the order of 20 atm. The increase of the moisture stress up to a level of 8 atm did not affect the germination percentage significantly. The presence of salts in the germination medium inhibited germination to an extent more than that due to moisture stress alone. Seeds failing to germinate in salt solutions with osmotic values higher than 12 atm were able to germinate when washed with water.The present investigation shows that the seeds of Z. occineum have the ability to germinate under a wide variety of conditions. This represent an adaptation to the drastic prevailing conditions in the habitat of this plant.