| This experiment was conducted to study the effects of chlormequat chloride?CCC?,mepiquat chloride?Pix? and paclobutrazol(PP333),on the growth as well as physical and chemical indices of tomato plug seedlings.The plant growth retardants?PGRs? were applied by foliar sprays or media drenches at different concentrations to discuss the effects of the PGRs applied on the morphological indices,physiological indices and photosynthetic characteristics of tomato plug seedlings.This could provide references for controlling excessive growth and improving seedling quality in industrial seedling-raising technique as well as for studying mechanism of chemical control and applying chemical control technology.The conclusions are as follows:The PGRs applied had a significant effect on the height, hypocotyl length, stem diameter, fresh weight and dry weight of tomato seedlings. Spraying with 200 or 300mg·L-1 chlormequat chloride,30 mg·L-1 mepiquat chloride,or 150mg·L-1 paclobutrazol or drenching with 200m·L-1 chlormequat chlorid or 50 or 70m·L-1 mepiquat chloride resulted in excessive growth suppression and a significant increase in stem diameter. Retardation effect of PGRs decreased with time and tomato seedlings grew normally afterwards.With the PGRs applied,the root/top ratio and seedling vigor index of tomato seedlings were increased. Compared with the control group, spraying with 200 or 300mg·L-1 chlormequat chloride increased seedling vigor index by 50.85% and 40.34% respectively; drenching with 200 mg·L-1 chlormequat chloride increased the root/top ratio and seedling vigor index by 42.86% and 29.03%; spraying with 30 mg·L-1 mepiquat chloride increased the root/top ratio and seedling vigor index by 54.17% and 46.98% respectively; drenching with 50 or 70mg·L-1 mepiquat chloride caused great increase in the root/top ratio, and increased the seedling vigor index by 50.80% and 43.34% respectively; spraying with 150 mg·L-1 paclobutrazol increased the root/top ratio and seedling vigor index by 52.78% and 24.53% respectively.With the PGRs applied,the root vigor,leaf chlorophyll content,proline content and activities of antioxidative enzymes of tomato seedlings were increased, and malondialdehyde?MDA? content was decreased. As a result, the harm of accumulation of active oxygen species to the cell was reduced and the seedlings were more resistant. Spraying with 200 or 300mg·L-1 chlormequat chloride,30mg·L-1 mepiquat chloride,or 150mg·L-1 paclobutrazol or drenching with 200mg·L-1 chlormequat chloride or 50mg·L-1 mepiquat chloride produced the best possible results.PGRs applied have a major effect on the photosynthetic characteristics of tomato seedlings. Spraying with 200 or300 mg·L-1 chlormequat chloride,30mg·L-1 mepiquat chloride, or 150mg·L-1 paclobutrazol or drenching with 200m·L-1 chlormequat chloride or 50m·L-1 mepiquat chloride greatly enhanced photosynthesis, which was conducive to the process of physiological metabolism.Therefore it is concluded that spraying with 200 or 300mg·L-1 chlormequat chloride,30mg·L-1 mepiquat chloride,or 150 mg·L-1 paclobutrazol when there were two leaves and one bud or drenching with 200m·L-1 chlormequat chloride or 50 or 70m·L-1 mepiquat chloride before raising seedling produced the best possible results and were recommended to be applied in production. |
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