Response of senescing rice leaves to flooding stress

Abstract

Flooding stress (FS) induced changes in pigment and protein contents and in photochemical efficiency of thylakoid membranes of chloroplasts were investigated during senescence of primary leaves of rice seedlings. Leaf senescence was accompanied by loss in 2,6-dichlorophenolindophenol (DCPIP) photoreduction, rate of oxygen evolution, quantum yield of photosystem 2 with an increase in MDA accumulation, and non-photochemical quenching (NPQ) of chlorophyll fluorescence. These changes were further aggravated when the leaves during this period experienced FS. The increase in NPQ value under stress may indicate photosynthetic adaptation to FS.Additional key words: adaptation to stress; carotenoids; chlorophyll; non-photochemical quenching; photosystem 2; quantum yield; senescence.--Prolonged water-logging of rice plants is a major problem in rice growing countries. The work conducted so far to understand the mechanism of damage and adaptation of photosynthetic apparatus of green plants experiencing flooding stress (FS) is meager (Mauchamp and Methy 2004, Panda et al. 2006). The photosynthetic apparatus, especially its photosystem (PS) 2 is very sensitive to different abiotic stresses (Strasser and Tsimilli-Michael 2001, 2006, Deo et al. 2006. The degree of stress induced damage and stress adaptations can therefore be examined by monitoring the behaviour of the photosystem exposed to FS.Most of the studies related to stress have been conducted in developing or mature leaves with scant regard to investigate the stress response in senescence phase. This is why we examined the photosynthetic response of leaves of a local cultivar of rice plant subjected to FS. The primary leaves of intact rice seedlings experiencing flooding stress were used for measurement of PS2 photochemistry during senescence to examine the stress induced damage of the photosystem and the possible adaptation mechanism the leaves develop to counter the stress effect.FS was imposed by growing the rice seedlings on soil in submerged conditions as described by Panda et al. (2006). Rice (Oryza sativa L. cv. Swarna) seedlings were grown in 0.15×0.15 m pots with soil from the rice field around the campus of Sambalpur University for 7 d in continuous "white fluorescent light" (60 μmol m -2 s -1 ) at 25±2 ºC in the laboratory. One set of 7-d-old seedlings was completely submerged in a thermocol tank of depth 0.6 m till 15 th d whereas another set kept without submergence was taken as control. The photosynthetic response of plants to FS was studied during senescence (11-15 d) phase. In all cases the primary leaves of the rice seedlings were used for experiments. Pigments were extracted from leaves with chilled 80 % acetone. Estimation of chlorophyll (Chl) was performed spectrophotometrically as per Arnon (1949) and that of carotenoids as per Liaaen-Jensen and Jensen (1971). Total protein extracted from leaves was estimated following the method of Lowry et al. (1951). Chloroplasts from primary leaves of rice seedlings were isolated and 2,6-dichlorophenol indophen...

Responses of the antioxidative enzymes in Malaysian rice (Oryza sativa L.) cultivars under submergence condition

“…These results suggest that submergence is associated with the induction of oxidative stress in rice plants, as peroxidation of membrane lipids as well as loss of thiol groups are indicators of oxidative stress. Lower levels of MDA indicate better submergence tolerance (Ella et al 2003;Mishra et al 2008;Yordanova and Popova 2007). However, MR219-4 and MR219-9 cultivars had significantly lower MDA level than nonsubmerged control at 8 days submergence, and still maintained until 12 days submerged for MR219-4 cultivar.…”

“…There is a possibility that chlorophyll content decreased because of MDA accumulation. MDA accumulation is likely to further aggravate and dismantle the PS2 complex (Mishra et al 2008). Under stress, ROS production is high resulting in oxidative damage.…”

Evaluation of light-harvesting complex proteins as senescence-related protein markers in detached rice leaves

“…In conclusion, the level of Lhca4 protein expression as well as other Lhc proteins such as Lhca2, Lhcb4 and Lhcb6 can be easily utilized as senescence-related protein markers in rice leaves. The rice plant is the most important food crop worldwide and a common monocotyledonous model plant for genetic analysis; therefore, it is expected that the use of Lhc proteins as the molecular protein markers of senescence will be useful in future studies of senescence in rice (Liu et al 2008, Mishra et al 2008.…”

Photosynthetic traits of Carex cinerascens in flooded and nonflooded conditions

“…Soil flooding reduces photosynthetic rates in many wetland plants (Pezeshki 2001). The decline in photosynthesis under flooding has been attributed to stomatal closure (Bradford 1983) and some metabolic inhibition (Pezeshki et al 1993, Liao and Lin 1994, Mishra et al 2008. Production of ethylene (Pallas andKays 1982, Taylor andGunderson 1988), decrease of Chl content (Bradford 1983, McKevlin et al 1995 and ribulose-1,5-biosphosphate carboxylase/oxygenase (Rubisco) activity (Pezeshki 1994) have been reported playing an important role in the photosynthetic decrease after soil flooding.…”