Effect Of Plant Growth Regulators On Growth State And Quality Of Yam Growing In South China

This study was carried out to research on effect of different plant growth regulators on growth and quality of yam(Dioscorea opposita Thunb.)from south China and to look for effective concentration and category of plant growth regulators.Yam variety,Guihuai No.2,was used in this study.In 2006,6 kinds of plant growth regulators were adopted as samples for experiments. Based on the yield and growth state of plants,chlormequat chloride(CCC)and CC(choline chloride)+NAA(naphthalene acetic acid)were picked out for studying on their effect on growth state and quality of yam.The results showed as follows.1.To spray chlormequat chloride could coordinate nutrition of yam leaves in the middle-late period of tuber growth.To spray the low concentration of chlormequat chloride and CC+NAA could hardly influence on N content of yam leaves.However,to increase concentration of CCC and CC+NAA used to treat yam could maintain high level of N content of leaves in the late period of leaf growth so as to delay aging of leaves.If yam was sprayed with chlormequat chloride which concentration was 2,250mg/L,P content of leaves would be enhanced and decrease of K content of leaves would slow down in the late period.2.To spray chlormequat chloride could effectively improve photosynthesis of yam in the middle-late period.To spray chlormequat chloride(2,250mg/L)could delay decrease of chlorophyll content of leaves, raise significantly net photosynthetic rate and transpiration rate and stomatal conductance of leaves,speed up synthesis and accumulation of dry matter so that the yield of yam could be raised. 3.To spray chlormequat chloride could promote decomposition and conversion of yam starch.To spray chlormequat chloride(2,250mg/L)could raise significantly amylase activity of leaves and be helpful for transport of storage substance from source to bank.To spray chlormequat chloride which concentration was 1,750mg/L or 2,250mg/L or CC 225mg/L+ NAA 20mg/L respectively could raise ADPG pyrophosphorylase activity of yam in the late period of tuber growth and benefit for starch synthesis and raise the yield of starch.4.To spray chlormequat chloride could raise the yield and improve the yield component.If the yam was sprayed with chlormequat chloride(2,250mg/L),yield of tuber per ha would reach 33,255.15kg,which was higher 15.20%and 13.22%than yield of CK and yam sprayed only with KH₂PO₄(0.15%)respectively.Yam grew tubers in the optimal proportion and 94.66%yam grew a tuber or two only.The average length of tuber was 61.1cm,which showed that to spray chlormequat chloride could promote growth and extension of tuber.To spray chlormequat chloride(2,250mg/L)was helpful for raising dry matter content,yield of fresh yam,content of water-soluble extracts and alcohol-soluble extractive,and wouldn't affect significantly on edible quality of soluble total sugar at the same time.That could also promote elevation of starch content in yam and maintain high content of protein as raising yield and starch content of yam so as to pledge that yam possessed good edible quality and flavor.Therefore,to spray chlormequat chloride(2,250mg/L)would be helpful for growth of yam from south China in the middle-late period and elevating quality of tuber under this experimental condition.