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The role of Euglena gracilis paramylon in modulating xylem hormone levels, photosynthesis and water‐use efficiency in Solanum lycopersicum L

Scartazza, Andrea, Picciarelli, Piero, Mariotti, Lorenzo, Curadi, Maurizio, Barsanti, Laura, Gualtieri, Paolo
Physiologia plantarum 2017 v.161 no.4 pp. 486-501
Euglena gracilis, Solanum lycopersicum, abiotic stress, abscisic acid, air, carbon dioxide, carboxylation, cell membranes, dose response, drought, elicitors, granules, jasmonic acid, leaf water potential, mesophyll, photosystem II, salicylic acid, sap, tomatoes, transpiration, water use efficiency, xylem
β‐1,3‐glucans such as paramylon act as elicitors in plants, modifying the hormonal levels and the physiological responses. Plant hormones affect all phases of the plant life cycle and their responses to environmental stresses, both biotic and abiotic. The aim of this study was to investigate the effects of a root treatment with Euglena gracilis paramylon on xylem hormonal levels, photosynthetic performance and dehydration stress in tomato (Solanum lycopersicum). Paramylon granules were processed to obtain the linear fibrous structures capable to interact with tomato cell membrane. Modulation of hormone levels (abscisic acid, jasmonic acid and salicylic acid) and related physiological responses such as CO₂ assimilation rate, stomatal and mesophyll conductance, intercellular CO₂ concentration, transpiration rate, water‐use efficiency, quantum yield of photosystem II and leaf water potential were investigated. The results indicate a clear dose‐dependent effect of paramylon on the hormonal content of xylem sap, photosynthetic performance and dehydration tolerance. Paramylon has the capability to enhance plant defense capacity against abiotic stress, such as drought, by modulating the conductance to CO₂ diffusion from air to the carboxylation sites and improving the water‐use efficiency.