Studies On Physiological And Biochemical Foundations And Control Technology Of Lignification In Asparagus (Asparagus Officinalis L.)

Effects of temperature (7, 13, and20 ), gibberellic acid (the concentration of 50 g-g-1 for asparagus, 20 g.g-1 for pea seedlings), abscisic acid (50 g.g-1 for asparagus, 10 g.g-1 for pea seedlings ), ethylene (10 L.L-1) GSH Clg.L-1), ethanol (2%) and 1-Methylcycloprope (1 L.L-1) on lignification and qualities of green asparagus (Asparagus officinalis L., cv. Mary Washington 500) and excised pea seedlings (Pisum sativum L.) were studied in this paper. Changes in total phenol content, active oxygen content, RNA content, DNA content , cell wall composition and PAL, PPO, CAD, POD activities were analyzed. The results obtained will be useful for inhibiting the deposition of lignin in asparagus and improving the quality at room temperature.The chlorophyll and soluble sugar content of green asparagus and pea seedlings declined during storage period, and the contents of free amino acid, fiber, cell wall polysaccharides, lignin increased. The reduction in chlorophyll, soluble sugar levels and the increase in free amino acid, fiber, cell wall polysaccharides, lignin levels were enhanced by ABA and ethylene , however substantially inhibited by low temperature, GA, MCP, GSH and ethanol. The fiber level stored at 20 was 55.1 % or 33.7% higher than that stored at 7 or 13 , respectively. .The cell wall polysaccharides and lignin content treated by GA, MCP, GSH or ethanol was 44.6%, 27.6%, 20.9% or 12.5% and32.8%, 30.8%, 22.3% or 29.3% lowerthan that of control.The correlation between lignin deposition and O2- content , H2O2 content, PAL ,CAD or POD activity was positively significant. The correlation between lignin deposition and coumaric acid, caffeic acid, ferulic acid, protein or DNA content was negatively significant. No statistically significant correlation was obtained between lignin deposition and total phenol content, RNA content or PPO activity. The O2- and H2O2 content of green asparagus increased during storage period, and the contents of protein, DNA and RNA decreased. The activities of PAL, CAD and POD increased at early storage period, but declined thereafter. The increase in O2 , H2O2 levels and the reduction in protein, DNA, RNA , PAL, CAD, POD activity levels were enhanced by ABA, ethylene and inhibited by GA, MCP, GSH and ethanol. The lignification in different part of green asparagus was varied. The contents of lignin, DNA, RNA and O2" in base were higher than those of in apex. The same trend was observed in PAL, CAD and POD. But the DNA and RNA in apex decomposed faster than those of in base.In a word, the mechanism of postharvest toughening in green asparagus including three aspects. First, the increase of PAL, CAD and POD activities lead to the rapid accumulation of lignin in asparagus. Second, the increase of O2- and H2O2 content will strengthen the cross-links between lignin and cellulose , hemi-cellulose . Third, with the break down of protein, DNA and RNA, lignin , cellulose and hemi-cellulose accumulated substantially because of serious senescence. Whether the postharvest lignification is attributable to the separate action or the cooperated action of the three aspects is not known.These results suggested that the quality of excised pea seedlings was improved by GA or low temperature, and the declining of chlorophyll, protein, sugar levels and increasing of cell wall polysaccharides and lignin content in green asparagus were significantly suppressed by GA, MCP, and ethanol. It was shown that the green asparagus treatment with GA, MCP, and ethanol maintained excellent quality and high commodity rate.