The aqueous extract and powder of the brown alga Dictyota dichotoma (Hudson) differentially alleviate the impact of abiotic stress on rice (Oryza sativa L.)

Abstract

Algal supplements can improve crop productivity and afford protection against abiotic stress by virtue of their rich content of plant nutrients and bioactive compounds. The present work investigates the relative efficiency of the biomass and extract of the brown alga Dictyota dichotoma in protection of rice against salinity and water stress. Rice (Oryza sativa L.) cv. Sakha 101 was grown on a silty clay soil amended with the aqueous extract and powder of D. dichotoma under NaCl and PEG 6000 stress at water potential of -0.492 MPa. Abiotic stress, particularly water stress, reduced rice growth and concentrations of K ? and protein but increased soluble sugars, starch, proline and Na ? concentrations of plant tissues, with counterbalancing effect of algal amendment. The benefit of algal amendment was greater for algal extract than algal powder and under water stress than salt stress. Algal amendment and abiotic stress promoted catalase and peroxidase activities in rice leaves with variable effect on polyphenol oxidase. The benefit of D. dichotoma to rice can be related to macro-and micro-nutrients, growth hormones, phenolics, flavonoids, sterols, vitamins and fucoidan. The production of toxic intermediates as a result of fermentation of the algal biomass in the paddy soil might reduce the benefit of algal amendment. Although rice is salt-sensitive, it is more resistant to salt stress than to drought stress. The ability of rice to retain Na ? in the root is pivotal for stress resistance, but the role of K ? partitioning is less evident.

Algal amendment improved yield and grain quality of rice with alleviation of the impacts of salt stress and water stress

“…Elucidation of the stress-induced changes in rice grain composition would help to assess the grain nutritional quality in a changing environment. The effect of treatments (algal amendment and abiotic stress) on rice yield resembled their effect on vegetative growth reported by El-Katony et al. (2020) for the same rice cultivar.…”

“…The relatively severe impact of WS compared with SS on rice yield, demonstrated in the present work, as well as on the vegetative growth of rice reported by El-Katony et al. (2020) can be explained in light of the fact that salt ions might serve as cheap osmotica to counterbalance the osmotic factor of SS.…”

“…The response of mineral content of rice grain to treatments simulated those of the vegetative stage reported by El-Katony et al. (2020) but to a limited extent.…”

“…Several safe and efficient organic amendments, such as plant growth promoters ( Quiroga et al., 2020 ), organic manures ( Srivastava et al., 2019 ) and seaweed extracts ( El-Katony et al., 2020 ) have been proven to enhance plant performance and to mitigate the severity of abiotic stress. Furthermore, organic amendments have the advantage of improving soil structure and capacity to hold water and nutrients beside enhancement of the beneficial soil microflora and fauna.…”

“…Salt stress and water stress were imposed by applying isosmotic solutions of NaCl and PEG 6000, respectively at Ψ w of -0.492 MPa. Details of preparation of algal extract, nutrient solution and stress solutions were outlined in El-Katony et al. (2020) .…”