Winter wheat (Triticum aestivum L.) is frequently subjected to stress that causes early senescence of plants and cessation of grain filling. This research evaluated chemical desiccation for selecting genotypes for tolerance to postanthesis stress and determined the relationship of chemical desiccation tolerance to carbohydrate and N partitioning. Twenty‐eight cultivars with a wide range of stress tolerance and yield potential were treated with 0 and 0.19 mol L‐1 NaCIO3 14 d after anthesis. The 2‐yr study was on a Eudora silt loam (coarse‐silty, mixed, mesic Fluventic Hapludoll); treatments were in randomized‐complete blocks with four replications. Ten cultivars representing a range of treatment responses were evaluated further at two locations on dryland and irrigated Eudora silt loam and Pratt loamy fine sand (sandy, mixed thermic Psammentic Haplustalf) in split plots with three replications. Cultivars that had high kernel weights and early release dates were generally more tolerant of chemical desiccation than cultivars with low kernel weights and recent release dates. Grain yields of chemically desiccated plants under irrigation correlated significantly with yields of untreated plants at one location but not at another location. Losses of dry matter and soluble carbohydrates, but not of N, from stems were related to grain yield response to chemical desiccation. We concluded that chemical desiccation effectively selects for postanthesis stress resistance, and that combining high carbohydrate reserves with efficient translocation to the grain should improve wheat performance in unfavorable environments.
Using a recombinant luminescent Nitrosomonas europaea assay to quantify biological nitrification inhibition (BNI), we found that a wild relative of wheat (Leymus racemosus (Lam.) Tzvelev) had a high BNI capacity and releases about 20 times more BNI compounds (about 30 ATU g −1 root dry weight 24 h −1 ) than Triticum aestivum L. (cultivated wheat). The root exudate from cultivated wheat has no inhibitory effect on nitrification when applied to soil; however, the root exudate from L. racemous suppressed NO À 3 formation and kept more than 90% of the soil's inorganic-N in the NH þ 4 -form for 60 days. The high-BNI capacity of L. racemosus is mostly associated with chromosome Lr#n. Two other chromosomes Lr#J, and Lr#I also have an influence on BNI production. Tolerance of L. racemosus to NH þ 4 is controlled by chromosome 7Lr#1-1. Sustained release of BNI compounds occurred only in the presence of Plant Soil (2007) 299:55-64
BackgroundThe use of plants and their derived substances increases day by day for the discovery of therapeutic agents owing to their versatile applications. Current research is directed towards finding naturally-occurring antioxidants having anticancer properties from plant origin since oxidants play a crucial role in developing various human diseases. The present study was designed to investigate the antioxidant and anticancer properties of Sygygium fruticosum (Roxb.) (abbreviated as SF).MethodsThe dried coarse powder of seeds of SF was exhaustively extracted with methanol and the resulting crude methanolic extract (CME) was successively fractionated with petroleum ether, chloroform and ethyl acetate to get petroleum ether (PEF), chloroform (CHF), ethyl acetate (EAF) and lastly aqueous (AQF) fraction. The antioxidant activities were determined by several assays: total antioxidant capacity assay, DPPH free radical scavenging assay, hydroxyl radical scavenging assay, ferrous reducing antioxidant capacity and lipid peroxidation inhibition assay. The in vivo anticancer activity of SF was determined on Ehrlich’s Ascite cell (EAC) induced Swiss albino mice.ResultsAll the extractives showed strong antioxidant activities related to the standard. The total antioxidant capacity (TAC) of the fractions was in the following order: EAF>AQF>CME>PEF>CHF. The TAC of EAF at 320 μg/mL was 2.60±0.005 which was significantly higher (p < 0.01) than that of standard catechin (1.37 ± 0.005). The ferrous reducing antioxidant capacity of the extracts was in the following order: EAF>AQF>CME>AA>CHF>PEF. In DPPH free radical scavenging assay, the IC50 value of EAF was 4.85 μg/mL, whereas that of BHT was 9.85 μg/mL. In hydroxyl radical scavenging assay and lipid peroxidation inhibition assay, the EAF showed the most potent inhibitory activity with IC50 of 43.3 and 68.11 μg/mL, respectively. The lipid peroxidation inhibition assay was positively correlated (p < 0 .001) with both DPPH free radical scavenging and hydroxyl radical scavenging assay. The total phenolic contents of SF were also positively correlated (p < 0 .001) with DPPH free radical scavenging, hydroxyl radical scavenging and lipid peroxidation inhibition assay. Based on antioxidant activity, EAF was selected for cytotoxic assay and it was found that EAF inhibited 67.36% (p < 0.01) cell growth at a dose of 50 mg/kg (ip) on day six of EAC cell incubation.ConclusionsOur results suggest that EAF of seeds of SF possess significant antioxidant and moderate anticancer properties. Seeds of SF may therefore be a good source for natural antioxidants and a possible pharmaceutical supplement.
Plants confront an extent of abiotic stresses due to environmental hardship, among which salinity is one of the major abiotic stresses that seizes plant growth and development resulting in a massive yield loss worldwide. Plants respond to salinity in two distinct phases: a quick osmotic phase and a sluggish ionic phase also known as hyper osmotic phase. Plants adjustment and/or tolerance to salinity stress comprise several complex physiological, biochemical and molecular networks. A widespread understanding of how plants response to salinity stress at different phases, and a cohesive physiological and biochemical approaches are crucial for the development of salt adapted and/or tolerant varieties for salt-affected areas. Researchers have identified several adaptive responses to salinity stress at cellular, biochemical and physiological levels, even though mechanisms triggering salt stress adaptation and/or tolerance are far from being entirely understood. This article bestows a spacious review of foremost research advances on physiological and biochemical mechanisms governing plant adaptation and/or tolerance to salinity stress relevant to environmental sustainability and as well as food production.
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