Antioxidative Defense System, Pigment Composition, and Photosynthetic Efficiency in Two Wheat Cultivars Subjected to Drought1

Abstract

We analyzed antioxidative defenses, photosynthesis, and pigments (especially xanthophyll-cycle components) in two wheat (Triticum durum Desf.) cultivars, Adamello and Ofanto, during dehydration and rehydration to determine the difference in their sensitivities to drought and to elucidate the role of different protective mechanisms against oxidative stress. Drought caused a more pronounced inhibition in growth and photosynthetic rates in the more sensitive cv Adamello compared with the relatively tolerant cv Ofanto. During dehydration the glutathione content decreased in both wheat cultivars, but only cv Adamello showed a significant increase in glutathione reductase and hydrogen peroxideglutathione peroxidase activities. The activation states of two sulfhydryl-containing chloroplast enzymes, NADP ؉ -dependent glyceraldehyde-3-phosphate dehydrogenase and fructose-1,6-bisphosphatase, were maintained at control levels during dehydration and rehydration in both cultivars. This indicates that the defense systems involved are efficient in the protection of sulfhydryl groups against oxidation. Drought did not cause significant effects on lipid peroxidation. Upon dehydration, a decline in chlorophyll a, lutein, neoxanthin, and ␤-carotene contents, and an increase in the pool of de-epoxidized xanthophyll-cycle components (i.e. zeaxanthin and antheraxanthin), were evident only in cv Adamello. Accordingly, after exposure to drought, cv Adamello showed a larger reduction in the actual photosystem II photochemical efficiency and a higher increase in nonradiative energy dissipation than cv Ofanto. Although differences in zeaxanthin content were not sufficient to explain the difference in drought tolerance between the two cultivars, zeaxanthin formation may be relevant in avoiding irreversible damage to photosystem II in the more sensitive cultivar.

Drought tolerance in cereals in terms of water retention, photosynthesis and antioxidant enzyme activities

“…As a consequence of drought stress the concentration of proline in plant leaves may increase to 80% of the total free amino acid content [5]. In response to severe drought stress, a rapid decline in the chlorophyll and protein contents may occur [6], accompanied by a rise in the proline level and the accumulation of simple sugars (e.g. sucrose, glucose and fructose) [2,7].…”

Effect of Salinity Stress on Antioxidant Defense System of Niger (<i>Guizotia abyssinica</i> Cass.)

“…Progressive elevation of H 2 O 2 in salt stressed Niger suggested imposition of greater degree of stress with increasing concentration of NaCl and time of exposure ( Table 2). Apart from serving as signaling molecules, elevated levels of H 2 O 2 are found to accelerate HaberWeiss reaction forming OH − , which in turn, causes lipid peroxidation [27]. Although H 2 O 2 levels peaked at 300 mM during 72 h, there was no corresponding increase in MDA ( Table 2), probably due to onset/reinforcement of antioxidant systems [28] as suggested for groundnut [29] and soybean [30] under salt stress.…”

Nitrogen level affects growth and reactive oxygen scavenging of fenugreek irrigated with wastewater

“…Under normal conditions, these ROS are well regulated by cell metabolism but under abiotic stress, they may exceed the scavenging capacity of the antioxidant system. The wastewater contained heavy metals which may enhance the level of H 2 O 2 which can result in the formation of hydroxyl radicals that can cause lipid peroxidation (Loggini et al 1999). Oxidative damage to bio-membranes of plants can be primarily attributed to the presence of Cd, a redox active metal catalyzing the generation of hydroxyl radicals and O 2 - (Arora et al 2002).…”