Gas exchange and leaf metabolism of irrigated maize at different growth stages

Net ecosystem exchange (NEE), leaf gas exchange and biochemical traits were investigated in an irrigated maize crop grownunder Mediterranean conditions. Sub-optimal irrigation water supply determined a drought stress during the early vegetativegrowth stage (45-49 days after swing) that decreased NEE. Drought, in the late vegetative stage, also caused a reduction ofleaf gas exchange. In the latter period, proline, glycine and serine, as well as sucrose leaf contents increased, while starch,proteins and glucose contents decreased. In the early reproductive stage, the crop experienced a longer dry spell that induceda reduction in canopy as well as in leaf gas exchanges, while protein and free amino acid contents decreased with respect tothe late vegetative stage. Either ecophysiological or biochemical data demonstrate a good capacity of cultivar PioneerPR32D99 to endure the environmental stress, related to Mediterranean summer drought, leading to an elevated dry matter yield at harvest. Photosynthetic apparatus appeared fairly resistant to soil water shortage due likely to the increased leafcontent of organic solutes, such as amino acids and soluble sugars.