Abstract
The seedlings of twenty eight annual and perennial desert plants belonging to fifteen families were raised under controlled growth conditions and subjected to a range of tests. The water use efficiency, photosynthesis, extreme temperatures and drought tolerance were monitored. The results were discussed for their ecological significance as a basic information to applied research. Seedlings which were more tolerant to extreme high and low temperatures and drought were more capable of controlling water loss through better water use efficiency. At temperatures below 25 °C, the annual plants had higher photosynthetic rate than perennials, whereas at higher temperatures, the perennials were advantaged.