واکنش برخی صفات مورفولوژیکی، عملکرد و اجزای عملکرد لوبیا (Vigna sinensis L.) به محلول‌پاشی متانول در شرایط تنش خشکی

Introduction

Drought stress is one of the major issues in reducing plant yield, especially in arid and semi-arid regions. This stress induces various physiological, biochemical, and molecular responses in crops as a survival mechanism, and more than any other environmental factor, it limits their production and yield. Also, drought stress can damage photosynthesis in crop plants and reduce growth, development, and grain yield. One important strategy to increase CO2 concentration in plants is the use of alcohol compounds such as methanol, which can enhance CO2 concentration and aid photosynthesis and growth under drought stress conditions. Therefore, the objective of this experiment was to evaluate the response of some morphological traits, yield, and yield components of cowpea to methanol foliar application under drought stress conditions.



Materials and Methods

The experiment was conducted as a split plot based on randomized complete block design (RCBD) with three replications in the summer of 2021 at Dezful region. Drought stress was applied based on irrigation intervals at four levels (80, 110, 140, and 170 mm of evaporation from a class A evaporation pan) as the main factor. Foliar spraying was performed at four levels (0, 10, 20, and 30% volumetric methanol solution with 2 grams per liter of glycine) as the sub-factor. The evaluated traits included plant height, number of leaves, number of pod per plant, number of grain per pod, 100-grain weight, grain yield, biological yield and harvest index. Analysis of variance was performed using statistical analysis system (SAS ver. 9.3). The means were compared using the Duncan's multiple range test at 5% probability level.



Results and Discussion

The results of this study showed that drought stress could reduce cowpea grain yield by reducing plant height, shedding leaves and flowers, and negatively affecting yield components. While, methanol foliar spray treatment had a positive and significant effect on all studied traits, and this effect reached its maximum in foliar spray with 30% volumetric methanol. Based on the comparison of the treatment means, the highest plant height (159.64 cm), number of leaves per plant (69.72), number of pods per plant (60.01), number of grains per pod (12.67), 100-grain weight (20.01 g), grain yield (2260 kg/ha), biological yield (4712 kg/ha), and harvest index (48.01%) belonged to foliar application of 30% volumetric methanol under irrigation conditions after 80 mm evaporation, and the lowest values belonged to the treatment combination of no foliar application of methanol (control) under irrigation conditions after 170 mm evaporation. Therefore, it seems that methanol foliar spraying is effective due to several mechanisms, including improving plant photosynthesis, reducing oxidative stress, improving water and nutrient absorption, changing plant metabolism, increasing vegetative growth, improving flowering and pod formation, moderating the effect of drought stress, and ultimately, it increased the final yield of cowpeas.



Conclusion

Based on the results of this study, the use of methanol foliar spraying, especially its application 30% volumetric, can increase cowpea grain yield under drought stress conditions by improving some morphological traits such as plant height and number of leaves per plant, as well as yield components (number of pods per plant, number of grains per pod, grain weight).

Results and Discussion

The results of this study showed that drought stress could reduce cowpea grain yield by reducing plant height, shedding leaves and flowers, and negatively affecting yield components. While, methanol foliar spray treatment had a positive and significant effect on all studied traits, and this effect reached its maximum in foliar spray with 30% volumetric methanol. Based on the comparison of the treatment means, the highest plant height (159.64 cm), number of leaves per plant (69.72), number of pods per plant (60.01), number of grains per pod (12.67), 100-grain weight (20.01 g), grain yield (2260 kg/ha), biological yield (4712 kg/ha), and harvest index (48.01%) belonged to foliar application of 30% volumetric methanol under irrigation conditions after 80 mm evaporation, and the lowest values belonged to the treatment combination of no foliar application of methanol (control) under irrigation conditions after 170 mm evaporation. Therefore, it seems that methanol foliar spraying is effective due to several mechanisms, including improving plant photosynthesis, reducing oxidative stress, improving water and nutrient absorption, changing plant metabolism, increasing vegetative growth, improving flowering and pod formation, moderating the effect of drought stress, and ultimately, it increased the final yield of cowpeas.



Conclusion

Based on the results of this study, the use of methanol foliar spraying, especially its application 30% volumetric, can increase cowpea grain yield under drought stress conditions by improving some morphological traits such as plant height and number of leaves per plant, as well as yield components (number of pods per plant, number of grains per pod, grain weight).