| Amino acid fertilizers are known as natural stimulators of plant growth and are widely used to promote crop yield and quality.Several researchers have demonstrated the influence of various amino acid fertilizers as foliar sprays in several plant species.However,the effects of amino acid water-soluble fertilizer on plant growth,physiology,and postharvest quality of peppers are still unclear.The objective of the first and second studies was to determine the effects of different concentrations of amino acid water-soluble fertilizer on growth,physiological indices,yield,and nutritional quality of pepper.The third study examined the postharvest performance of pepper grown with amino acid water-soluble fertilizer and CK at different storage temperatures.The fourth study investigated the effects of 1-MCP treatments on the storage stability of nutritional properties,enzyme activities,MDA,and volatile compounds of pepper pretreated with amino acid water-soluble fertilizer and CK for 12 days.Subsequently,four series of experiments,namely CK（control）,T1(270kg ha-1 amino acid water-soluble fertilizer),T2(405 kg ha-1 amino acid water-soluble fertilizer),and T3(540 kg ha-1amino acid water-soluble fertilizer)were conducted under field and greenhouse conditions in 2020 and 2021,respectively.（1）The results of the effects of amino acid water-soluble fertilizer on plant morphology,physiological characteristics and mineral uptake of plant organs under field and greenhouse conditions showed,that treatment with 540 kg ha-1 amino acid water-soluble fertilizer increased plant stem diameter（15.03 and 16.86%）,root activity（20.06 and 55.77%）,magnesium in roots（22.42 and 13,78%）,stomatal conductance（47.50 and 42.25%）in both experiments,and net photosynthetic rate（47.50%）only in field experiment compared to control.Soil amendment with 405 kg ha-1 of amino acid water-soluble fertilizer had high nitrogen content（47.52 and 30.37%）,calcium in roots（47.32 and 61.04%）,and Y（NPQ）（62.75 and 56.67%）in both experiments,while transpiration rate was highest only in the field experiment.Fertilization with 270 kg ha-1 amino acid water-soluble fertilizer increased plant height,chlorophyll and carotenoid content,improved chlorophyll fluorescence such as ETR,Y（ii）,Fv/Fm and Qp.It also increased calcium in leaves（47.31 and 55.53%）,nitrogen in roots（35.22 and 35.90%）,iron in leaves（59.51 and 60.30%）in both experiments compared to control.（2）The application of amino acid water-soluble fertilizer during plant growth and fruit development on yield,pepper quality parameters,and bioactive compounds showed that treatment with 270 kg ha-1 amino acid water-soluble fertilizer increased fruit chlorophyll content,fruit firmness（69.81 and 59.90%）,fresh weight（10.78 and 34.72%）,and dry weight（47.98 and 51.93%）of pepper,capsaicin（64.83 and 65.78%）and dihydrocapsaicin（84.23 and 55.56%）,resulting in higher fruit pungency（67.89 and 39.53%）,vitamin C（72.32 and 55.56%）,soluble protein（20.18 and 39.53%）,fruit calcium content（35.18%and 35.67%）,higher essential and non-essential amino acids,and accumulation of lower nitrate content in field and greenhouse conditions.Fertilization with 405 kg ha-1 of amino acid water-soluble fertilizer was the best to produce longer fruit length and higher yield（22.21 and 22.20%）,color and carotenoids in field and greenhouse conditions,respectively.This study also showed that higher application of amino acid water-soluble fertilizer(540kg ha-1)resulted in higher soluble sugar（9.02 and 12.86%）and manganese content（60.85and 10.88%）and fruit copper content in field and greenhouse conditions.（3）Postharvest performance of amino acid water soluble fertilizer treatments and CK grown pepper（"Hangjiao No.2"）at different storage temperatures provided evidence that storage behavior of pepper pretreatment with amino acid water-soluble fertilizer was related to fruit characteristics at harvest.The results of this study showed that the nutritional quality of pepper such as capsaicin,dihydrocapsaicin,and vitamin C,fruit chlorophyll content,soluble protein,and fruit firmness decreased with increasing storage period in both high（22±2℃）and cold（10℃）storage in all categories of stored pepper.However,the decrease in these quality parameters was much lower in 270 kg ha-1 pepper grown with amino acid water-soluble fertilizer at the end of storage,resulting in higher fruit quality of these pepper fruit.Amino acids and soluble sugar content increased to a maximum at day 9 and then decreased at the end of storage in pepper pretreated with 540 or 405 kg ha-1 of amino acid water-soluble fertilizer and in the CK,respectively.In addition,the MDA and nitrate content of pepper fruit in all categories of stored pepper increased with advancing storage days and then decreased at the end of storage,with lower concentration in 270 kg ha-1 of amino acid water-soluble fertilizer.The results clearly show that the higher the postharvest quality of green chilies of the cultivar"Hangjiao No.2",the lower the quality loss during short-term storage.（4）Positive effects of 270 kg ha-1 amino acid water-soluble fertilizer and CK grown pepper randomly selected and treated with 0.5,1.0,and 1.5μL L-1 1-MCP on storage stability of nutrient content,antioxidant enzyme activities,MDA content,and volatile profile of pepper fruit during storage were found.The study found that the application of 1-MCP to the pretreated pepper inhibited the increase in nitrate content and further delayed the degradation of chlorophyll,vitamin C,and protein content of"Hangjiao No.2"pepper grown with amino acid water-soluble fertilizer than CK pepper.In addition,1-MCP had the greatest effect on the activities of antioxidant enzymes such as SOD,POD and CAT,decreased the accumulation of MDA in the pepper grown with amino acid water-soluble fertilizer than in the CK pepper.However,the 1-MCP treatments had no significant effect on the shelf-life of this pepper cultivar during the 12-day storage period.Weight loss increased significantly with increasing storage time,with lower weight loss in amino acid water-soluble fertilizer grown pepper than in CK pepper.However,treatment with 1.0μL L-1 1-MCP further reduced the percent weight loss in both categories of stored pepper.The study also showed that pepper grown with amino acid water-soluble fertilizer and CK contained 88 and 81 volatile compounds,respectively,with terpenes dominating,followed by aldehydes,esters,alcohols,alkanes,acids,phenol derivatives,ketones,and other volatile compounds whose content was lower in CK grown pepper.Significant volatile compounds,including aldehydes,esters,alkanes,and alcohol classes in"Hangjiao No.2"pepper treated with 1.0μL L-1 1-MCP showed higher retention during storage period compared to the other treatments applied to pepper grown with amino acid water-soluble fertilizer while 1.5μL L-1 1-MCP was the most suitable concentration of all treatments for CK pepper.Taken together,these results indicate that soil amended with 270 kg ha-1 amino acid water-soluble fertilizer had the optimal effect in field and greenhouse conditions and can be used as a substitute for synthetic fertilizers to improve the growth and yield of pepper,strengthen bioactive compounds in pepper fruit which in turn positively affect post-harvest quality of pepper while the application of the highest amino acid water-soluble fertilizer(540 kg ha-1)may be detrimental to fruit quality,as most quality parameters obtained were very low compared to the lower concentration of fertilizer applied(270 kg ha-1).The results suggest that when amino acid water-soluble fertilizer is applied at harvest,post-storage effects should be minimal.This represents a new strategy for improving the nutraceutical potential and economic value of pepper,with important implications for the bioeconomy and the environment.Thus,the amino acid water-soluble fertilizer is an effective tool both for research and for more sustainable horticulture and improving food security. |
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