Studies On The Effects Of Chitosan On Growth Physiological Machanism And Quality Of Broccoli

Chitosan, a nature high molecular weight cationic polysaccharide, is normally obtained by the alkaline deacetylation of chitin. Chitosan and its derivatives have a wide range of applications due to their low toxic ,antibacterial activity,edibility and biodegradability, They have been employed, for example, to solve numerous problems in medical , agriculture ,foodstuff environmental and chemical engineering. Because the molecular structure of chitosan is similar with the structure of cell wall, it has great significance to be applied in plants as a new plant growth regulator.1.Seeds of Broccoli were film-coated with chitosan of different concentration.Our results showed that film-coating with chitosan had no significant effect on fresh weight of ground parts and roots of Broccoli seedlings.And there was no significant effect on the absorption of N and K.But film-coating significantly improved the content of chlorophyll and protein in seedling leaves. It also improved the dry weight of ground parts and roots of cauliflower seedlings. Film-coating with chitosan of appropriate concentration can increase the content of total soluble sugar and N in seedling leaves. Film-coating with chitosan significantly improved the content of free ammonium ,the activity of NR, GDH and GS, and film-coating markedly increased photosynthetic captivity and photochemical efficiency of PS II reaction center( PS II).2.We sprayed chitosan on "zhulv"and "shanshui"-two variation of Broccoli under salt stress to investigate the effect of chitosan on salt tolerant of Broccoli.The results showed chitosan significantly increased the germination percentage, germination index and vigor index of Broccoli seeds and increased the salt tolerance index of Broccoli seedings. The effect was more significant on seeds of low germination percentage.Under salt stress ,chitosan significantly decreased the MDA content and membrane permeability of Broccoli leaves.Activities of SOD,POD and PPO in Broccoli leaves was significantly promoted treated with chitosan . Proline content in leaves continuously increased ,while protein content continuously decreased. Reducing sugar content changed little .Content of sucrose and totalsoluble sugar decreased a little under low salt concentration and increased late with the increase of salt concentration.It indicated that plants decompose macromolecular substances to small molecule substance to improve their tolerance captivity under stress.3.Spraying with chitosan of different concentration significantly increased the content of chlorophyll ,anthoxanthin ,chlorogentic acid, polyphenal ,soluble protein and total soluble sugar of Broccoli flowers. 40 mg L-l chitosan showed the most remarkable effet,compared to control, the content ofchlorophyll ,anthoxanthin ,chlorogentic acid, total soluble sugar and soluble protein of treated Broccoli flowers increased by 64.4%,282.5%,35.6%,16.2% 22.7% respectively.PAL and PPO are key enzymes in synthesize of phenolics.No relation was found between phenolics synthesize and PAL activity in Broccoli flowers,but it showed positive relation between phenolics synthesize and PPO activity.