Influence of water stress on antioxidative enzymes and yield of banana cultivars and hybrids.

The main aim for this field experimental study is to screening of various banana cultivars and hybrids for water deficit tolerance through antioxidative enzymes and yield. The field experiment was conducted at National Research Centre for Banana to screen the banana cultivars and hybrids for water deficit tolerance and to elucidate information on antioxidative enzymes mechanism correlated with yield of banana cultivars and hybrids. The methodology of this experimental were analyzed by split plot design and has two treatments considered as main plot (M) viz., control plot taken as M1 and water deficit plot taken as M2 and also the cultivars and hybrids were considered as sup plots (S). The stress was imposed according to the Available Soil Moisture (ASM) and this ASM was measured by using pressure plate membrane apparatus. The experimental data were significantly varied between the treatments and also cultivars and hybrids. The antioxidative enzymes of catalase, super oxide dismutase and ascorbate peroxidase were significantly enhanced during water deficit conditions. Among the twelve cultivars and hybrids, Karpuravalli, Karpuravalli x Pisang Jajee, Saba and Sannachenkathali was identified as tolerant to water stress with highly accelerated by water stress treatment in the range of 23 to 32% over Control in Catalase (CAT), Super Oxide Dismutase (SOD) and Ascorbate Peroxidase (APX) leads to reduced the cellular membrane damaged by reactive oxygen species and get higher yield; whereas, Matti, Pisang Jajee x Matti, Matti x Anaikomban and Anaikomban x Pisang Jajee were notified as sensitive cultivars and hybrids with lesser increase in antioxidative enzyme activity of 15% than control which is leads to get very low yield.

Nitrophenolates spray can alter boll abscission rate in cotton through enhanced peroxidase activity and increased ascorbate and phenolics levels.

Field studies were conducted from 2002 to 2005 to evaluate foliar spray of Atonik (a plant growth regulator (PGR) containing nitrophenolates) on cotton boll abscission rate by assessing various reactive oxygen species (ROS) contents, antioxidant content and antioxidant enzyme activity from 1 to 9 days after anthesis (DAA). The result indicated that the nitrophenolate spray reduced hydrogen peroxide (H(2)O(2)), superoxide anion (O(2)(-)) accumulation, lipid peroxidation (malondialdehyde--MDA), lipoxygenase (LOX) activity and membrane permeability relative to the control. Antioxidant enzyme activity (superoxide dismutase, SOD; ascorbate peroxidase, APX; peroxidase, POX; glutathione peroxidase, GSH-Px) was significantly increased by the nitrophenolate spray. The POX (217%) and GSH-Px (242%) activities were enhanced compared with APX (7.7%) activity at 9 DAA. Enhanced accumulation of ascorbate (245%), phenol (253%) and proline (150%) was observed in nitrophenolate-sprayed plants compared with control at 9 DAA. Because ascorbate content is increased by higher dehydroascorbate reductase (DHAR) enzyme activity, the ascorbate was able to replenish reducing equivalents to phenoxyl radicals, resulting in an increase of phenolic compounds. The increased phenolic acid content may be involved in scavenging the ROS produced in developing cotton boll. The role of DHAR and glutathione reductase (GR) in keeping higher levels of reduced ascorbate and low levels of endogenous H(2)O(2) in the developing cotton boll may be the prerequisite for boll retention. Based on the present work, we conclude that nitrophenolate-sprayed plants counteracted the deleterious effects of ROS by the peroxide/phenolics/ascorbate system, which causes reduced boll abscission and increased yield.