|Author:||Nunes, C©Łtia ; Fevereiro, Manuel Pedro Salema ; da Silva,Anabela Bernardes ; de Sousa Ara©ðjo, Susana ; da Silva, Jorge Marques|
|Book Group Author:||NA|
In Medicago truncatula Gaertn. cv. Jemalong plants some mechanisms involved in drought resistance were analysed in response to a progressive water deficit imposed by suppression of soil irrigation. Withholding water supply until the soil had reached one-half of its maximum water content had no significant effect on leaf RWC, gas exchanges or chlorophyll fluorescence parameters. Under severe drought conditions, the plants resistance to water shortage involved mainly drought avoidance mechanisms through a decrease in stomatal conductance. The consequent decrease in the internal CO₂ concentration (C i) should have limited the net CO₂ fixation (A). Since A decreased slightly more than C i under severe water deficit, non-stomatal limitations of photosynthesis may have also occurred. Analysis of A/C i curves showed reduced carboxylation efficiency due to limitations in RuBP regeneration and Rubisco activity, confirming the presence of non-stomatal limitations of photosynthesis. Drought tolerance mechanisms involving osmotic adjustment and an increase in cell membrane integrity were also present. Altogether, these mechanisms allowed M. truncatula cv. Jemalong plants to still maintain a quite elevated level of net CO₂ fixation rate under severe water deficit conditions. These results may contribute to identify useful physiological traits for breeding programs concerning drought adaptation in legumes.
|Pages:||289 - 296|
|Journal:||Environmental and experimental botany|
stomatal conductance, photosynthesis, chlorophyll,fluorescence, ribulose 1,5-diphosphate, cell membranes, irrigationrates, ribulose-bisphosphate carboxylase, osmotic pressure, waterstress, plant physiology, Medicago truncatula, drought, droughttolerance, plant-water relations, gas exchange, plant available water,soil water content