Topic: Chemistry
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Reduction of transpiration through foliar application of chitosan
In this study, we investigate the potential of chitosan, a natural beta-1-4-linked glucosamine polymer, to reduce plant transpiration. Chitosan was appliedfoliarly to pepper plants and water use was monitored. Peppers were grown in pots ingrowth-chambers, where transpiration was measured by weighing pots. In an accompanying field study, water use was determined by monitoring soil moisture depletion with time domain reflectometry.
An automated irrigation system replenished the water used each day. Plant biomass and yield were determined to calculate biomass-to-water ratios. Differences in canopy resistance between control and chitosan treated plants were analyzed with the aid of the Penman-Monteith equation. Scanning electron microscopy (SEM) and histochemical analyses demonstrated that chitosan induced closure of the plant'sstomata, resulting in decreased transpiration. Foliar application of chitosan reduced water use of pepper plants by 26-43%while maintaining biomass production and yield. We suggest that chitosan might bean effectiveantitranspirant to conserve water use in agriculture.
Chitosan is a natural, biodegradable polysaccharide polymer which serves as major structural component of the exoskeleton of crustaceans and insects (Muz- zarelli, 1977). Chitosan, together with other polysac- charidesand proteins, is also found in the cell walls of a variety of fungi. Chitosan is commercially derived from shells of crabs, shrimp, and lobsters. These shells accumulate as waste byproducts of shellfish processing.
Chitosan induces the expression of a variety of genes involved in plant defense responses, that, in some cases, result in increased synthesis of sec- ondaryplant metabolites (Loschkeetal., 1983; Walker-Simmonsetal., 1983). Transcriptional activation, induced by both chitosan and jasmonicacid, of genes encoding phenylalanine ammonia lyase and protease inhibitors, suggests that chitosan may influence pathways involvingjasmonic acid (Walker-Simmons et al., 1983; Farmer and Ryan, 1990; Doaresetal., 1995). Jasmonates exhibit some activities similar to the plant hormone abscisic acid (ABA), which plays a key role in the regulation of water use by plants (Sembdnerand Parthier, 1993). Increased levels of ABA resultinclosure of stomata and reduced transpiration
Source: akasha.wsu.edu
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