Some ecophysiological characteristics of artà (Calligonum comosum L' Hérit) in response to drought stress

Water deficit is an important environmental factor restricting plant growth and photosynthesis. The effect of water deprivation on leaf water status, photosynthetic gas exchange, chlorophyll content and fluorescence parameters of artà (Calligonum comosum) was studied. Five-month-old artà seedlings, grown in pots in the open air, were subjected to one of four drought treatments (i.e., mild, moderate, severe and extreme drought stress) and compared to control seedlings (normal watering regime). Results show that leaf water potential, net photosynthesis, stomatal conductance, transpiration, photosynthetic pigment content (chlorophyll a and b) decreased with increasing levels of drought stress. Inactivation of the photosynthetic apparatus was accompanied by changes in the fluorescence characteristics, providing evidence that reduction of photosynthetic rate could be attributed to non-stomatal limitations. Alterations imply changes in photochemical conversion efficiency of photosystem Ⅱ by which plants could reduce water transpiration or protect their photosynthetic apparatus from destruction. These adaptations are discussed in relation to the strategies developed to grow drought-resistant artà seedlings in desert environments.