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Agriculture, around the globe, is facing great challenges including the need to increase the production of nutrient-dense food and to withstand climate change's impact on water and soil conservation. Among these challenges, drought stress is considered the most overwhelming danger for the agriculture sector. Organic plant growth ingredients are frequently used to enhance the growth and production of field crops cultivated in normal and unfavorable conditions. The present study was designed to explore whether leaves extracted from various landraces of Moringa could play a defensive role against drought stress in rice. Seedlings were grown under three water conditions, i.e., normal conditions (control; 100% field capacity), moderate (75%), and severe drought (50%). Leaf extracts obtained from four Moringa landraces were used as foliar spray at the tillering, panicle initiation, and grain filling stages of cultivating rice plants. The levels of water stress negatively influenced photosynthetic pigment synthesis, gas exchange traits, antioxidant activities, and yield and grain quality parameters. Leaf extracts, at the rate of 3%, from all the landraces significantly enhanced the biochemical, physiological, and yield-related attributes of rice plants under normal and unfavorable growth conditions. Particularly, leaf extract from the Faisalabad landrace was the most effective biostimulant to increase photosynthetic (8.2%) and transpiration (13.3%) rates, stomatal conductance (8.3%), chlorophyll a (15.9%) and b (9.7%) contents, and carotenoids (10.4%) as compared to water spray. The maximum photosynthesis rate was observed at 14.27 µmol CO2 m−2 s−1 via application of leaf extract from the Faisalabad landrace followed by the DG Khan (13.92 µmol CO2 m−2 s−1) and Multan (13.9 µmol CO2 m−2 s−1) landraces, respectively. Improved grain yield (25.4%) and grain quality (an increase of 10.1% in amylose with a decrease of 2.8% in amylopectin) in rice plants along with enzymatic activities such as catalase (21.2%), superoxide dismutase (38.6%), and ascorbate peroxidase (24.3%) were observed at the peak after application of leaf extract from the Faisalabad landrace. The maximum grain yield of 53.59 g per plant was recorded when using Faisalabad landrace leaf extract and the minimum (40 g) using water spray. It is concluded from the findings of the current experiment that leaf extract from the Faisalabad landrace possesses higher biostimulant potential than other landraces and can be applied to mitigate the adverse impacts of drought stress with higher productivity and improved grain quality of rice. [ABSTRACT FROM AUTHOR]

Population growth, food shortages, climate change and water scarcity are some of the frightening challenges being confronted in today's world. Water deficit or drought stress has been considered a severe limitation for the productivity of rice, a widely popular nutritive cereal crop and the staple food of a large portion of the population. A key stage in crop growth is seed emergence, which is mostly constrained by abiotic elements such as high temperatures, soil crusting and low water potential, which are responsible for poor stand establishment. Seed priming is a pre-sowing treatment of seeds that primes them to a physiological state that allows them to emerge more proficiently. The purpose of this study was to investigate the potential of leaf extracts from local and exotic moringa landraces as seed priming agents in rice cultivated under water deficit (75% field capacity) and control conditions (100% field capacity). Rice seeds were placed in an aerated solution of moringa leaf extract (MLE) at 3% from three obtained landraces (Faisalabad, Multan and an exotic landrace of India). The results obtained from the experimentation show that the water deficit regime adversely affected the studied indicators including emergence and growth attributes as well as physiological parameters. Among the priming agents, MLE from the Faisalabad landrace significantly improved the speed and spread of emergence of rice seedlings (time to start emergence at 23%, emergence index at 75%, mean emergence time at 3.58% and final emergence percentage at 46%). All the priming agents enhanced the growth, photosynthetic pigments, gas exchange parameters and antioxidant activities, particularly under the water deficit regime, but the maximum improvement was recorded by the MLE from the Faisalabad landrace. Therefore, the MLE of the Faisalabad landrace can be productively used to boost the seedling establishment and growth of rice grown under normal and water deficit conditions. [ABSTRACT FROM AUTHOR]