Studies On Effects Of Salicylic Acid On Pollination, Fertilization And Phenol Metabolism In Pear (Pyrus L.)

Salicylic acid (SA) is an endogenous signal substance that exists universally in the plant, which has been confirmed as a new hormone, and plays a crucial role in regulation of physiology and biochemistry action. Good pollination and fertilization is the basis of high-quality fruit; On the other hand, metabolism of phenols can directly affect the fruit quality. Therefore it has an important significance to improving the quality of fruit and revealing biology sense of salicylic acid by studying the effect of SA on the two aspects. This experiment studied the effects of SA on pollination, fertilization and phenol metabolism in Ya-li pear and Xue-li pear. The main results were as follows:1. SA existed in the flower of Ya-li pear. With blooming there was a marked peak of SA content and it appeared at the day after blooming, the maximal value attained 266.58 μg.g-1 FW. Then the content of SA dropped gradually, and ascended within a narrow range at the fifth day after blooming.2. It improved the rate of fruit setting by spraying 0.02 mmol.L-1 SA in florescence. Spraying 0.002 and 0.2 mmol.L-1 SA can only improve the rate of fruit setting after two weeks of bloom, yet there was unobvious divergence between treatments and control after June drop.3. The releasing rate of ethylene was a jump pattern in florescence, the peak appeared at the day after blooming. It was reduced by spraying 0.0002 and 0.002 mmol.L-1 SA, and was inhibited and maintained in a low level all along by 0.02 and 0.2 mmol.L-1 SA.4. Spraying SA of different concentrations in florescence resulted in the increase of endogenous GAs content of Ya-li pear pistil. ABA content was reduced with spraying 0.0002, 0.002, 0.02mmol.L-1 SA. IAA content was also reduced by 0.0002 and 0.002 mmol.L-1 SA. Only spraying 0.2 mmol.L-1 SA that improved the contents of IAA and ABA in the pistil.5. With 0.002, 0.02mmol.L-1 SA liquid cultivating Ya-li pear flower branchs, it prolonged the life of pistils, enhanced the activity of peroxidase (POD), supereoxide dismutase (SOD) and decreased the content of malondialdehyde (MDA), superoxide anion radical (O2-). There was only a short-term increasing effect on 0.0002 mmol.L-1 SA on the two enzymes, so the accumulation of MDA and O2 was relieved temporarily. Pistil apolexising was accelerated under the concentration of 0.2 mmol.L-1 SA treatments, meanwhile the POD and SOD activity were inhibited, MDA and O2 contents were raised.6.The treatments of 0.0002,0.002,0.02 mmol.L-1SA improved the pollen activity of Ya-li pear and Xue-li pear, moreover accelerated germinating of pollen and extending of pollen tube.7.0.0002, 0.002, 0.02 mmol.L-1 SA treatments antagonized the inhibition of EGTA on germination of pollen and extending of pollen tube, and the same to LaCl3. But the accelerating action of SA on pollen was neglected by using CaCl2; only individualtreatment of SA was obviously higher than control.8. The inhibitions of LiCl and Neomycin on germination and extending of pollen tube were antagonized by 0.0002, 0.002, 0.02mmol.L-1 SA, it was more marked at the situation of higher concentration of LiCl and Neomycin.9.The result showed that successive spraying 0.02mmol.L-1 SA inhabited polyphenoloidase (PPO) activity during mature period of fruit and decreased the number of fruit spots, the size of stone cell, content of phenols and lignin. But 0.002 and 0.02 mmol.L-1 SA treatments improved the activity of POD in fruit.