Differential growth, yield and biochemical responses of maize to the exogenous application of Kappaphycus alvarezii seaweed extract, at grain-filling stage under normal and drought conditions

Maize is sensitive to water stress at flowering and grain-filling stages and thus strategies for the mitigation of stress and improving the yield sustainably would be beneficial. Two factorial pot experiments were carried out to assess the efficacy of a biostimulant product obtained from Kappaphycus alvarezii in conjunction with recommended rate of fertilizers (RRF), in mitigating moderate and severe stress in maize. The plants were subjected to normal as well as water deficit conditions following which Kappaphycus alvarezii seaweed extract (KSWE) was applied foliarly only once at the grain-filling stage along with a suitable control (water spray + RRF). Growth and yield parameters along with antioxidant enzymes, metabolites and reactive oxygen species content in leaves were studied. The results revealed that water deficit conditions (moderate and severe) significantly (p < 0.001) reduced the yield in both the trials, by 22 and 74% as compared to plants receiving the normal irrigation schedule, while KSWE increased the yield by 14% and 23% (p < 0.01), respectively. KSWE applied once at the grain-filling stage increased seed yield only under normal condition and not under stress conditions in both the seasons. The increase in seed yield observed under the KSWE treatments was predominantly through the increase in all the yield attributes, especially, cob length, the number of grains per cob and length of grain fill, however, the 100-seed weight remained unaltered. Increased activities and concentrations of enzymatic and non-enzymatic antioxidants due to KSWE application with concomitant reduction in reactive oxygen species, such as O2− and H2O2 levels, both under normal and stressed conditions, resulted in a lesser degree of oxidative stress in KSWE treated plants. Thus, the results revealed that a single application of KSWE, even at a late crop stage can be beneficial under normal irrigated condition.