## 4 Discussion
### Chlorophyll Fluorescence  
The primary reaction of every crop to drought stress is the closing of the stomata to avoid losing water via transpiration. The closing of stomata might be due to a prompt reaction to control the water level in leaves [72] or a reduced rate of moisture in the air. The closing of the stomata controls CO2 absorption, which prompts oxidative harm and no photosynthate uptake. Stomata closing likewise upsurges the heat dispersal in leaves [73]. Also, the pigments of photosynthesis and the thylakoid membrane are harmed by drought stress. The decreased chlorophyll composition within the drought episodes has likewise been accounted for [74]. Notwithstanding, a few studies have elaborated a surge in chlorophyll composition in oats under water stress [36]. It appears to rely on the type of crop and variety. For example, chlorophyll composition in certain cultivars of a dark gram _Vigna mungo_ L was augmented while, in other cases, it was reduced in situations of water stress [75]. These can be ascribed to the varied changes in the activities of catalysts engaged in chlorophyll biosynthesis. It has been accounted for that the content of \"chlorophyll a\" was more relative to \"chlorophyll b\" within plants that were stressed under drought [76]. A decline in the chlorophyll a/b proportion was accounted for in the _Brassica_ species during drought [75]. The activities of the Rubisco catalyst in leaves rely on the rate at which the photosynthetic apparatus, including the stomata, functions [77]. Furthermore, significant harm is caused by the reduction in the Rubisco due to the reduction in its subunits. The binding of inhibitors like 2-Carboxyaribinitol 1-Phosphate to the catalytic site of Rubisco is also common under drought stress, which affects enzyme activity [78]. Likewise, other significant catalysts associated with photosynthesis are additionally adversely impacted by drought. The reduction in phosphorylation and debilitated ATP amalgamation have been accounted for as the central point restricting the photosynthetic process in mild drought periods [45]. The decreased generation of nicotinamide adenine dinucleotide phosphate NADP\({}^{+}\) during drought results in low control of the non-cyclic electron transportation link, lessening ATP production [79, 80]. Chlorophyll fluorescence analysis provides an in-depth insight into the photochemical and photosynthetic activities to depict plants' health and stress levels [81]. Drought strongly inhibits the process of photosynthesis. Under its influence, the probability of PSII damage, characterised by reduced photosynthetic efficiency and increased dissipation of absorbed energy in non-photochemical quenching, increases [82]. The measurements carried out record dynamic changes in PSII functioning under the influence of ongoing drought stress and the application of acid spraying. Initial fluorescence (F\({}_{0}\)) analyses the level of fluorescence when all the RCs (reaction centres) of the photosystems are open. Furthermore, it is a vital parameter to analyse a fully oxidised plastoquinone acceptor pool (QA) [83, 84]. An increase in F\({}_{0}\) indicates any disruption of energy transfer to the reaction centre [85]. For example, with PEG 5%, stress was noted in the second term, while later plants sprayed with MA and CA adapted to unfavourable environmental conditions. On the other hand, with PEG 7.5%, fluctuations in F\({}_{0}\) changes were shown, alternately positive and negative. Considering the average of the combinations, the acid treatment showed a positive effect on the increasing trend of F\({}_{\text{M}}\), indicating an improvement in PS II's functioning. The changes in F\({}_{\text{V}}\) trends varied dynamically. Lower values of this parameter lower the performance of PS II [86]. This generally reduced the field efficiency of PS II quantum (lower F\({}_{\text{V}}\)), which may result in greater dissipation of energy in the form of heat [87].