DO GERMINATION MECHANISMS DIFFER IN PLANTS ORIGINATING IN DESERTS RECEIVING WINTER OR SUMMER RAIN

Abstract

ABSTRACT Some of the perennial shrub species of the Mesembryanthemaceae from South Africa, growing in the Sde Boker Introduction Garden, were tested for seed germinability: species which originated in areas receiving winter rain were compared to species from regions receiving summer rain. Differences in germinability were found after exposure to high temperatures during the first 24 h of imbibition. In Bergeranthus scapiger, originating in areas receiving summer rain, imbibition at 45°C for 24 h did not inhibit but accelerated germination when seeds were later transferred to 25°C. The opposite was found in seeds of plants, such as one of the Cheiridopsis species, inhabiting areas of winter rain. Imbibition of seeds at 45°C for 24 h inhibited germination in the light and prevented it completely in the dark when transferred later to 25°C. In annual plants which inhabit the Negev highlands, such as Carrichtera annua (Cruciferae), imbibition of seeds at 35°C for 24 h inhibited germination more intensely in th...