| N-phenyl-phthalamic acid is a novel plant growth regulator,which has the favour able regulation effect on the growth-development of apples,cherries and other fruit tr ees.The previous results showed that phthalamic acid also exhibited good promotion on the growth and certain induction effect of capsicum,cowpea and other crops,how ever,its mechanism of action is still unclear.Therefore,based on the previous resear ch basis,this study selected for capsicum as the test plant and brassinolide as the co ntrol agent to determine effects of three different dosages(133.3,200.0 and 266.7 m g·L-1)of phthalamic acid on growth-development and endogenous hormones of capsic um plants,and capsicum seedlings resistance to drought and low temperature stress.The biological effects on crops were clarified from the perspective of physiology and biochemistry,so as to lay a foundation for further research on the mechanism of ac tion.The main results are as follows:?1?Phthalamic acid can promote the growth-development of capsicum plants.Field trials showed that the capsicum plants of the phthalamic acid treatment groups grew well.During the measurement period?7 d,14 d and 21 d after the second spraying?,compared with the blank control,the relative growth rate of capsicum height was increased by16.67-66.67%,which were treated by 133.3 mg·L-11 phthalamic acid;the net growth of stem diameter and flowering number of capsicum in the 200.0 mg·L-11 phthalamic acid treatment group were significantly improved by 74.83%-179.50%and 258.97%-481.92%,respectively;during the determination period,the 133.3mg·L-11 phthalamic acid treatment significantly increased the net photosynthetic rate and chlorophyll content of capsicum leaves,which was increased by 11.18%-23.39%and 29.19%-60.78%,respectively.Brassinolide treatment also had similar effects,except that the effect on the relative growth rate of capsicum height was significant,and the other regulation effects were weaker than that of phthalamic acid treatments.?2?Phthalamic acid can affect the content and proportion of endogenous hormones in capsicum leaves.In the bud,flowering and fruit stages,compared with the blank control,133.3 mg·L-11 phthalamic acid treatment can significantly increase theauxin?IAA?and reduce abscisic acid?ABA?content in capsicum leaves,which were increased by15.42%-26.03%and reduced by 22.25%-26.70%,respectively;the 266.7 mg·L-11 phthalamic acid treatment significantly increased the zeatin?ZR?content in capsicum leaves,which was23.41%-253.10%higher than the blank control;but the gibberellin?GA3?content in capsicum leaves was not obviously impacted by all phthalamic acid treatments;the ratios of IAA/ABA,ZR/ABA and GA3/ABA of 133.3 mg·L-11 phthalamic acid treated capsicum were significantly increased at the measurement period,and the IAA/ZR ratio increased at the fruiting period.The effects of brassinolide treatment on the endogenous hormone content and ratio were different from that of phthalamic acid treatments.?3?Phthalamic acid can increase the yield and improve the quality of capsicum.The results showed that in each treatment group,the effect of 133.3 mg·L-11 phthalamic acid treatment was the most obvious,which increased the yield by 37.91%compared with the blank control,and the single fruit weight,dry matter content and fruit shape index of capsicum increased by 14.75%,26.09%and 25.38%,respectively;the soluble sugar,soluble protein,vitamin C,capsaicin content of nutrient and flavor substances in fruits were also increased to some extent under phthalamic acid treatments.Brassinolide treatment was inferior to phthalamic acid in improving quality,but it showed the same effect on increasing yield,which was 38.01%higher than that of the blank control.?4?Phthalamic acid can induce the resistance of capsicum seedlings to low temperature stress.After 2 days of treatment with 133.3 mg·L-11 phthalamic acid?once?,capsicum seedlings were given moderate low temperature stress:12.5°C?16 h L?/7.5°C?8 h D?,which all grew well;and plant height,stem diameter,root-shoot ratio and seedling index compared with blank control were significantly increased by 7.79%,7.52%,16.46%and11.41%,respectively;the photosynthesis of capsicum seedlings was improved,during the measurement period,compared with blank control,the net photosynthetic rate,water use rate and chlorophyll content of capsicum seedlings were increased by 31.95%-44.74%,8.48%-71.10%and 17.59%-76.61%,respectively,and the stomatal limit value decreased by13.12%-37.01%;compared with the blank control,the antioxidant enzyme activities?SOD,POD,CAT?of capsicum seedlings were significantly increased,especially SOD activity increased by 21.04%-38.66%;the content of soluble sugar,soluble protein and free proline in capsicum seedlings were also significantly increased,which were 9.31%-65.92%,11.35%-20.89%and 41.24%-83.08%,respectively,compared with the blank control.In addition,under the mild:15??16 h L?/10?8 h?D?and severe:10??16 h L?/5??8 h D?low temperature stress,133.3 mg·L-11 phthalamic acid treatment before stress has a similar effect on capsicum seedlings.The effect of brassinolide treatment on the resistance of capsicum seedlings to low temperature stress was similar to that of phthalamic acid,but there were also some differences.?5?Phthalamic acid can induce the resistance of capsicum seedlings to drought stress.After 2 days of treatment with 133.3 mg·L-11 phthalamic acid?twice?,capsicum seedlings were given mild drought stress:50%-60%relative water content of soil,which all grew well;and plant height,root-shoot ratio and seedling index compared with blank control were significantly increased by 3.45%,20.21%and 23.20%,respectively,but no difference was found in stem diameter;the photosynthesis of capsicum seedlings was improved,during the measurement period,compared with blank control,the net photosynthetic rate,water use rate and chlorophyll content of capsicum seedlings were increased by 38.65%-61.04%,20.61%-33.63%and 13.30%-39.20%,respectively,and the stomatal limit value decreased by12.53%-17.66%;compared with the blank control,the antioxidant enzyme activities?SOD,POD,CAT?of capsicum seedlings were significantly increased,especially POD activity increased by 28.64%-65.78%;the content of soluble sugar,soluble protein and free proline in capsicum seedlings were also significantly increased,which were 21.57%-50.22%,33.46%-58.74%and 44.61%-72.92%,respectively,compared with the blank control.In addition,under the mild:15??16 h L?/10?8 h?D?and severe:10??16 h L?/5??8 h D?low temperature stress,133.3 mg·L-11 phthalamic acid treatment before stress has a similar effect on capsicum seedlings.The effect of brassinolide treatment on the resistance of capsicum seedlings to drought stress was better than that of phthalamic acid.In summary,phthalamic acid has obvious promotion and induction effects on the growth-development and stress resistance of capsicum.The effects of phthalamic acid treatments on capsicum growth-development are mainly through the regulation of endogenous hormones to promote plant growth-development,increase yield and improve fruit quality.By inducing and activating the antioxidant and osmotic regulation system of capsicum seedlings,the seedlings can resist the stress of low temperature and drought stress.As a kind of efficient and new plant growth regulator,phthalamic acid has the good application prospect in production practice. |
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