• Energy Research

Plant growth regulators are naturally biosynthesized chemicals in plants that influence physiological processes. Their synthetic analogous trigger numerous biochemical and physiological processes involved in the growth and development of plants. Nowadays, due to changing climatic scenario, numerous biotic and abiotic stresses hamper seed germination, seedling growth, and plant development leading to a decline in biological and economic yields. However, plant growth regulators (PGRs) can potentially play a fundamental role in regulating plant responses to various abiotic stresses and hence, contribute to plant adaptation under adverse environments. The major effects of abiotic stresses are growth and yield disturbance, and both these effects are directly overseen by the PGRs. Different types of PGRs such as abscisic acid (ABA), salicylic acid (SA), ethylene (ET), and jasmonates (JAs) are connected to boosting the response of plants to multiple stresses. In contrast, PGRs including cytokinins (CKs), gibberellins (GAs), auxin, and relatively novel PGRs such as strigolactones (SLs), and brassinosteroids (BRs) are involved in plant growth and development under normal and stressful environmental conditions. Besides, polyamines and nitric oxide (NO), although not considered as phytohormones, have been included in the current review due to their involvement in the regulation of several plant processes and stress responses. These PGRs are crucial for regulating stress adaptation through the modulates physiological, biochemical, and molecular processes and activation of the defense system, upregulating of transcript levels, transcription factors, metabolism genes, and stress proteins at cellular levels. The current review presents an acumen of the recent progress made on different PGRs to improve plant tolerance to abiotic stress such as heat, drought, salinity, and flood. Moreover, it highlights the research gaps on underlying mechanisms of PGRs biosynthesis under stressed conditions and their potential roles in imparting tolerance against adverse effects of suboptimal growth conditions.

Under a changing climate, harvesting management and exploiting the genotypic divergence of Egyptian clover cultivars offers a biologically viable solution to sustainably boost the milk productivity of dairy animals. Two multi-season field trials were executed under semi-arid conditions whereby the first experiment aimed to assess the potential of Egyptian clover cultivars (Berseem Agaiti, Anmol and SB-11) for nutritional quality attributes and the digestibility of green forage and hay, forage palatability and milk productivity of buffaloes fed on hay. In the second field investigation, new promising line, SB-11, was tested for seed production potential under varying dates of the last harvesting regimes (10, 20 and 30 March along with 9 April and 19 April) owing to a sharp hike in temperature. In terms of the nutritive value of green forage and hay, SB-11 remained superior for recording the maximum crude protein (CP), ash, fat and nitrogen-free extract except dry matter (DM) content that was exhibited by the Anmol cultivar. Additionally, SB-11 remained unmatched by giving a minimum crude fiber (CF), while Berseem Agaiti yielded the lesser nutritive forage by producing 4% and 2% higher CF than SB-11 and Anmol, respectively. Moreover, SB-11 recorded the maximum digestibility of CP and DM. Furthermore, SB-11 exhibited a 6% and 9% higher palatability along with 8% and 11% higher milk production than Anmol and Berseem Agaiti, respectively. Additionally, 20 March surpassed the rest of the cutting dates by exhibiting 7%, 23%, 50% and 207% more seed yield than 10 March, 30 March, 9 April and 19 April, respectively, indicating quite a pronounced effect of the last cutting management on the seed production potential of Egyptian clover. The research findings suggest SB-11 as a promising genotype for bridging the nutritive gap of quality feed (forage and hay) for buffaloes along with addressing the seed production challenge of Egyptian clover.

Globally, optimized doses of exogenously applied growth regulators hold the potential to sustainably boost the growth and productivity of leguminous crops, including green gram. A field investigation was undertaken at the Agronomy Farm of the University of Agriculture Faisalabad, Pakistan in 2021–2022 to determine the highest-performing doses of foliar-applied salicylic acid (S1 = 0 and S2 = 75 ppm) and gibberellic acid (G1 = 0, G2 = 30, G3 = 60, G4 = 90 and G5 = 120 ppm) for green gram (cv. NIAB-MUNG 2011) sown under irrigated conditions in a semiarid climate. The response variables included physiological growth traits (CGR and net assimilation rate (NAR)), yield attributes (plant height (PH), PBs and the number of pods per plant−1 (NP), pod length (PL) and SW, grain (GY) and biological yields (BY), the biosynthesis of pigments (chlorophyll a, chlorophyll b and total chlorophyll along with carotenoids) and protein (P) contents. The results revealed that S2G5 remained unmatched in that it exhibited the highest crop growth rate, while it remained on par with S2G4 and S2G3 in terms of its net assimilation rate. Additionally, S2G5 maximized plant height, the number of pod-bearing branches and pods per plant, pod length, seed number per pod−1 and 1000-seed weight, which led to the highest grain yield and biological yield (104% and 69% greater than those of the control, respectively). Moreover, the same treatment combination also surpassed the rest of the treatments because it recorded the largest amounts of chlorophyll and carotenoid contents, and the P content was increased to 24% greater than that observed for the control treatment. Thus, the exogenous application of salicylic acid (75 ppm) and gibberellic acid (120 ppm) might be recommended to green gram growers to sustainably increase the plant’s yield and nutritional value, and these findings may serve as a baseline for conducting more studies to test higher doses of these growth regulators.

For ensuring food security and imparting sustainability to modern commercial-oriented and highly intensive temperate farming systems, organic wastes from poultry and dairy industries constitute biologically viable strategy to improve crops productivity under changing climate. A field trial was undertaken to appraise the impact of broiler litter (BL = 5 tons ha−1), farm yard slurry (FYS = 10 tons ha−1), and chemical fertilizers including di-ammonium phosphate (DAP = 60 kg ha−1) and single super phosphate (SSP = 60 kg ha−1) applied solely and in conjunction with each other, along with a control treatment (NM). The synergistic fertilization regime encompassing BL+DAP triggered the vegetative growth of soybean as indicated by taller plants having thicker stems and higher leaf area per plant compared to NM. In addition, this fertilization management system improved reproductive yield attributes including pods number and 100-seeds weight which maximized the seed yield, harvest index, seed oil content, and biological yield by 66%, 5%, 31%, and 23% respectively than NM. Moreover, this fertilizers combination was followed by SSP + BL, while BL performed better than FYS and DAP remained superior to SSP. Furthermore, the correlation analyses indicated moderately stronger direct association of seed yield with vegetative growth traits and highly stronger linear relationship with reproductive yield attributes. Thus, co-application of broiler litter (5 tons ha−1) with reduced doses of DAP (60 kg ha−1) might be recommended to temperate soybean growers having access to poultry wastes.