I’ve written about two general strategies that plants employ to survive in desert habitats – succulence and drought-deciduousness. Today I’ll introduce the most successful adapters to life in the desert – drought-escaping plants. Plants escape drought in one of two ways. They either survive only as seeds or they use taproots.
Annuals are plants that wither and die during the dry seasons but not before completing their life cycle, sometimes in just a few weeks. Their seeds are covered by a thick protective coat and are dispersed, only to wait underground as part of the desert’s “seed bank”. Contained within their seed coats are certain chemicals that prohibit germination. The seeds must wait for rain to wash these chemicals away before they can sprout. These are the plants that amaze us here in Sinai when our desert sands are suddenly covered in green after a spring rainstorm. These are also the plants that are so important to the Bedouins’ herds of goats and sheep. Some of these annuals that survive dry seasons as seeds include Astragalus spp., Artemisia spp., Diplotaxis spp., and Tribulus spp. and are pictured below.
Using taproots is also a successful strategy to avoid the problems associated with drought. A taproot is a very thick and long root that grows directly downward. Think of a carrot. The taproot is the main central root which other smaller roots grow off of. The long taproot allows the plant to reach water stored deep underground, providing an almost constant source of water. The taproots of Convolvulus lanatus, pictured below, and Artemisia monosperma are also covered with a thick bark that helps the roots to withstand the withering caused by wind.
You can learn more about these desert plants in my book, Wandering through Wadis: A nature-lover’s guide to the flora of South Sinai.