Leaf gas exchange, water relations and photosystem-II functionality depict anisohydric behavior of drought-stressed mulberry (Morus indica, cv. V1) in the hot semi-arid steppe agroclimate of Southern India

Abstract

The present study was undertaken to characterize leaf gas exchange physiology and photoacclimation characteristics in drought-stressed mulberry cultivar V1 (Morus indica L.) grown under the hot semi-arid steppe agroclimate of Southern India. The experiment was conducted in year 2009 during peak summer months (April-June). Mulberry plants, grown in short rotation coppice system, were subjected to two irrigation regimes: the control plot received a regulated full-rate irrigation (weekly 2-3 times) and the drought-stressed plot received a regulated deficit irrigation (irrigated only once in a fortnight). Net photosynthesis, transpiration, stomatal conductance, leaf water potential (ΨL) and photosytem-II (PS II) efficiency were examined. In spite of significant down-regulation in leaf gas exchange, the drought-stressed stands still exhibited a considerable rate of photosynthesis along with significant concomitant decrease in ΨL, more conspicuously during midday (12.00-13.00h) depicting rather low stomatal control on ΨL, a behavior characterized as 'anisohydric'. The PS II structural and functional integrity was well-maintained, even in the drought-stressed plants. However, apparent photoacclimatory changes were recorded in drought-exposed stands including decrease in electron transport and enhanced thermal dissipation from PS II. Overall, our data demonstrate some of the important driving leaf-level mechanisms adopted by mulberry cultivar V1 to tolerate drought stress and sustain photosynthesis. © 2014 Elsevier GmbH.