Role of exogenous-applied salicylic acid, zinc and glycine betaine to improve drought-tolerance in wheat during reproductive growth stages.

BACKGROUND: Drought has become a dangerous threat to reduce crop productivity throughout the world. Exogenous applications of regulators, micronutrients, and/or osmoprotectants for inducing drought-tolerance in field crops have been effectively adopted. A controlled pot study was performed to investigate the relative efficacy of salicylic acid (SA), zinc (Zn), and glycine betaine (GB) as foliar applications on the growth, tissues pigments content, relative water content (RWC), leaf gas-exchange, antioxidant enzymes activity, reactive oxygen species (ROS) accumulation, osmolytes contents, and the yield parameters of wheat plants subjected to two soil water conditions (85% field capacity: well-watered, 50% field capacity: water-deficient) during reproductive growth stages. RESULTS: Water deficient conditions significantly decreased the growth, yield parameters, RWC, photosynthesis pigment, and gas-exchange attributes except for intercellular CO2 concentration. However, foliar applications remarkably improved the growth and yield parameters under water deficit conditions. Under drought condition, exogenous applications of SA, Zn, and GB increased the grain yield pot- 1 by 27.99, 15.23 and 37.36%, respectively, as compared to the control treatment. Drought stress statistically increased the contents of hydrogen peroxide (H2O2), superoxide anion radical (O2 •-), and malonaldehyde (MDA), and elevated the harmful oxidation to cell lipids in plants, however, they were considerably reduced by foliar applications. Foliar applications of SA, Zn, and GB decreased MDA content by 29.09, 16.64 and 26.51% under drought stress, respectively, as compared to the control treatment. Activities of all antioxidant enzymes, proline content, and soluble sugar were increased in response to foliar applications under water deficit conditions. CONCLUSIONS: Overall, foliar application of GB, SA, and Zn compounds improved the drought-tolerance in wheat by decreasing the ROS accumulation, promoting enzymatic antioxidants, and increasing osmolytes accumulation. Finally, GB treatment was most effective in thoroughly assessed parameters of wheat followed by SA and Zn applications to alleviate the adverse effects of drought stress.

Morpho-physiological responses of sunflower to foliar applications of chlormequat chloride (CCC) / Respostas morfo-fisiológicas de girassol para aplicacões foliares de chlormequat chloride (CCC)

Chlormequat chloride (CCC) is used to inhibit extension growth in cereals and promote branching and flowering in potted ornamental plants produced in greenhouses; however, experimental data on the use of CCC in field sunflower are limited. Field experiments were conducted to study the effect of foliar applications of CCC at rates of 3,000 g ha-1 (single application) and 3,000 plus 3,000 g ha-1 (double application) on the morphology and productivity of sunflower plants. CCC provoked some foliar injury on sunflower plants within a week after application, but the effect was transient; the symptoms were reduced over time and the plants recovered completely. Single application of CCC did not provide significant height reduction of sunflower plants as opposed to double application, which reduced plant height at maturity by 12.7% (or by 43.4 cm). Both application schemes promoted flowering and induced the production of more achenes, but finally resulted in reduced achene yield per plant by 17.8% and 20.3%, respectively, compared with the non-treated control. The achene yield reduction resulted by the reduction in the 100-achene weight. The study provides new evidence that allow a better understanding of the mode of action of CCC in sunflower. Overall, the foliar applications of CCC at the rates tested in this study either did not provide any advantage in terms of height reduction of sunflower plants or the height reduction achieved was accompanied by significant reduction in achene yield. On the basis of all the above, CCC does not appear to be a suitable growth regulator for the control of plant height in sunflower.

Chlormequat chloride (CCC) é usado para inibir o crescimento em altura em cereais e promover a ramificação e floração em plantas ornamentais envasadas produzidas em estufas; no entanto, os dados experimentais sobre o uso de CCC em girassol são limitados. Os experimentos de campo foram conduzidos para estudar o efeito de aplicações foliares de CCC a taxas de 3.000 g ha-1 (aplicação simples) e 3.000 + 3.000 g ha-1 (aplicação dupla) sobre a morfologia e a produtividade das plantas de girassol. A aplicação de CCC provocou algum dano nas folhas de girassol em uma semana após a aplicação, mas o efeito foi transitório; os sintomas foram reduzidos ao longo do tempo e as plantas recuperaram completamente. Aplicação simples de CCC não propiciaram redução significativa da altura de plantas de girassol em oposição à dupla aplicação, que provocou redução da altura das plantas, na maturidade, de 12.7% (ou 43.4 cm). Ambos os esquemas de aplicação promoveram floração e induziram a produção de mais aquênios, mas finalmente resultaram em redução do rendimento de aquênios por planta de 17.8% e 20.3%, respectivamente, em comparação com o controle não tratado. A redução de rendimento de aquênios foi provocada pela redução do peso de 100 aquénios, porque o número de aquénios enchidos não foi afectado significativamente. O estudo fornece novas evidências de que permitem uma melhor compreensão do modo de ação do CCC em girassol. No geral, as aplicações foliares de CCC nas taxas testadas neste estudo, ou não fornecem qualquer vantagem em termos de redução da altura de plantas de girassol, ou a redução da altura alcançada foi acompanhada de redução significativa no rendimento de aquênios. Com base no que precede, CCC não parece ser um regulador de crescimento adequado para o controle da altura das plantas em girassol.