Gas exchange and organic solutes in forage sorghum genotypes grown under different salinity levels

Trocas gasosas e solutos orgânicos em genótipos de sorgo forrageiro sob diferentes níveis de salinidade

ABSTRACT

Adaptation of plants to saline environments depends on the activation of mechanisms that minimize the effects of excess ions on vital processes, such as photosynthesis. The objective of this study was to evaluate the leaf gas exchange, chlorophyll, and organic solute in ten genotypes of forage sorghum irrigated with solutions of different salinity levels. The experiment was conducted in a randomized block design, in a 10 x 6 factorial arrangement, with three replications, using ten genotypes - F305, BRS-655, BRS-610, Volumax, 1.015.045, 1.016.005, 1.016.009, 1.016.013, 1.016.015 and 1.016.031 - and six saline solutions, with electrical conductivity (EC_w) of 0, 2.5, 5.0, 7.5, 10 and 12.5 dS m^-1. The photosynthetic activity in forage sorghum plants reduces with increasing salinity, and this response was found in the ten genotypes evaluated. The chlorophyll and protein contents were not affected by salinity, whereas carbohydrates and amino acid contents increased with increasing EC_w. Soluble sugars are essential for osmoregulation of forage sorghum due to its high content in leaves.

Key words:
salt stress; photosynthesis; chlorophyll; Sorghum bicolor (L.) Moench