Modification of water entry orchestrates long term drought acclimation of wheat leaves

• Published in: Plant and soil Vol. 347; no. 1-2; p. 179
• Main Authors: Bresta, Panagiota, Nikolopoulos, Dimosthenis, Economou, Garifalia, Vahamidis, Petros, Lyra, Dionyssia, Karamanos, Andreas, Karabourniotis, George
• Format: Journal Article
• Language: English
• Published: Springer 01.10.2011
• Subjects: Droughts; Greece; Health aspects; Physiological aspects; Stomata; Wheat; Xylem; Greece
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-011-0837-4

Immediate leaf functional responses to drought, such as stomatal closure and photosynthetic rate reduction, are already known from short-term studies. We tested the hypothesis that long-term acclimation of leaves to drought includes hydraulic and stomatal anatomical changes and that gas exchange and nitrogen allocation patterns are inevitably adjusted to the new structural status. 26 structural and functional traits in one sensitive cultivar (Simeto) and two drought resistant landraces (Ntopia Heraklion 184, Kontopouli 17) of field-grown wheat (Triticum turgidum L. var. durum) were examined under four water shortage levels. Drought acclimation responses were more intense in Simeto than in the two landraces. In accordance to the working hypothesis, drought-acclimated leaves showed lower hydraulic conductance due to narrower vessels and higher stomatal and vein densities than the control leaves, resulting in a safe mode of water transfer and consumption which is essential for the survival in water limiting conditions. Irrespectively of genotype and water regime, significant correlations among structural (hydraulic characteristics, stomatal and vein patterns) and functional (gas exchange, nitrogen content) parameters were found, indicating the functional adjustment to the new structural status. The Principal Component Analysis showed that these structure-function interactions reflected the trade-off between growth and protection against water losses (Axis 1), as well as the competition between different sinks (carbon gain vs structural reinforcement and reproductive effort) in N allocation (Axis 2). Drought acclimation in wheat leaf is integrally processed by the coordination of structural and functional parameters in order to compensate for the adverse effects of water shortage. This structure--function network that regulates the transition from normal growth-mode to protection- mode, includes at least two important "nodal points": xylem conducting efficiency (water entry) and stomatal function (water exit). This transition also includes the redirection of nitrogen resources to different sinks. Keywords Nitrogen * Photosynthesis * Stomata * Transpiration * Triticum aestivum * Water stress * Xylem