Effects Of Irrigation Amount On Relative Indexes Of Loquat’s Frost Resistance In Flowering And Young-fruit Stage In North Marginal Area

The loquat tree is green through all four reasons, which flowering and fruit setting in autumn and winter. Besides, the growth of loquat is in spring and the ripening time is during early summer. The critical time of blossom and fruit setting is winter and spring, in this period, the growth and yield of loquat is closely relate to the nutritional status and physiological metabolism of loquat tree. Ankang is located in Qinba mountainous area and which is belong to the north subtropical climate zone, in addition, it is also the northern marginal area of natural distribution of loquat in China. But, the strong cold air climate always make bad influence on this area, which led to the temperature cooling seriously, more serious is the radiation cooling, under this condition, the flower bud and young fruit of loquat will be damaged seriously, it also led to loquat fruit disorder and do harm to the flowering and fruit setting. The Changqizaosheng loquat as experimental material which is belong to Ankang area, the period of this experiment is from the end of August 2013 to the end of April 2014. During experiment, nine times irrigation treatment to the loquat is conducted. The irrigation amount is 10, 20, 30, 40 kg respectively and no irrigation as the contrast experiment, each group of treatment text includes three loquat trees and the irrigation area is limited to the tree disks. The soil moisture content and temperature should be measured before irrigation, beside, the samples of flower spikes and young fruit of loquat should be collected and then to determine the relative indexes through experiment. The period of this experiment is from the end of November 2013 to the end of April 2014. The aim of this experiment is study to the relationship between irrigation amount and relative indexes of frost resistance, and results will provide theoretical and technical reference to the cultivation and protection against cold conditions of loquat. The conclusions are as follows:(1) In the period of temperature drop, appropriate irrigation will be contribute to improve the soil moisture content and temperature during the loquat flowering and fruit bearing. As far as the soil moisture content and temperature, the condition of 30 kg or 40 kg irrigation amount is better than the condition of no irrigation or small irrigation amount. The former condition is benefit to keep the soil moisture content and temperature stability, thus meet the need of loquat growth.(2) The irrigation has little influence on the relative electrical conductivity of young fruit in January. According to the situation of no freezing damage in Ankang area, the low temperature has not do serious harm to young fruit during this experiment, it illustrates that low temperature stress is not seriously.(3) In the period of temperature drop, the low temperature stress to young fruit and flower of loquat can be relieved by irrigation. The soluble sugar, soluble starch and proline, SOD activity, pod activity, PAL activity are all decrease under the condition of 30 kg or 40 kg irrigation amount. The resistant ability of loquat is weak under the condition of no irrigation and the body is sensitive to low-temperature stress. As a result, the protection mechanism of loquat can activate in time when temperature drop. Appropriate irrigation volume can contribute to the loquat against low temperature stress and relieve the damage of low temperature.(4) In the cold month, the part of material content and enzymatic activity can be improved by the irrigation. The content of soluble protein and GSH increased under the condition of irrigation amount is 30 kg or 40 kg, besides, the PPO activity also increases. But, as far as no irrigation, the loquat is easily damaged by low temperature and the synthesis of soluble protein and GSH is restrained, in addition, the PPO activity also decreases.(5) The appropriate irrigation amount of 14-year-old loquat is 30 kg, which can meet the need of flowering and fruit setting under low temperature. In the period of temperature drop, the loquat which in Ankang area is irrigated 30 kg water every month. As a result, this treatment can contribute release the low temperature stress and improve the frost resistance of loquat.