Study Of Exogenous Hormones On Early Senescence And Mechanism In Sweet Pepper (Capsicum Frutescens L.vargrossum.Bailey)

The experiment was conducted with Zhongjiao 4 variety of sweet pepper, treated by exogenous hormones, to probe into probability and physiological mechanism for early senescence prevention during late growing season. The exogenous hormones of uniconazole (S3307), indolebutyric acid (IBA), α-naphthaleneacetic acid (NAA), 6-benzyladenine (6-BA), and gibberellic acid (GA3) were used in the experiment. Physiological indexes of the seedling were taken under coldness stress condition where the pepper seeds were soaked with S3307 and IBA and NAA, and the seedling growth, photosynthetic pigment content, root vigor, late season plant growth vigor, yield, chlorophyll, soluble protein, and superoxide dismutase (SOD) and peroxidase (POD) were also measured when S3307 and IBA and NAA soaked the seeds and 6-BA and GA3 treated the seedlings. Results obtained from the study were as follows:1. S3307 and IBA and NAA can improve the ability of the pepper seedling resistant to coldness stress when the seeds were soaked. It increased protection enzymes activities of SOD and POD and raised soluble protein and carbohydrates and praline content, which may result in damages reduction from MDA accumulation decline. Recommended concentration for S3307 and IBA and NAA were 5 and 10 and 10 mg L^-1, respectively. In addition, the effectiveness for increasing resistance of the seedling was higher for S3307 only than for IBA and NAA combination.2. Soaked seeds by S3307, it reduced significantly plant height of the pepper seedlings, increased stem diameter and dry matter weight and ratio of root to canopy and root vigor, improved greatly photosynthetic pigment content, lowered ratio of Chla to Chlb, and maintained the pepper grow vigorously indicated by lots of leaf numbers and high leaf area index in late growing season.3. Treated the pepper seedlings with GA3 at concentration of 50 mg L^-1, pepper grown well during early and middle seasons while early senescence were found in late season. Protection enzymes activities and chlorophyll content and soluble protein highly dropped, which were probably attributed to GA₃'s effect on carbohydrate allocation. GA₃ can enlarge pepper fruit capacity and let higher amount of assimilative matter be flown into fruit, which resulted in leafs and roots nutrient deficiencies relate to sudden senescence.4. When the seeds were soaked with IBA of 10 mg L^-1 and NAA of 10 mg L^-1 combination,...