Study On Microenvironment In Different Bags And Their Effects On Light Distribution In Canopy Apple

The paper studied the change of temperature and humidity in different bags during the development of Fuji apple and its effects on fruit appearance quality,and the distribution of relative light radiation in different tree shapes and investigate the effects of light. The main research results were as follows:1. Dynamic influence of outside environment on microenvironments in different paper bags. In sunny and mild days, the dynamic change curves of temperature in all the bags are just like mountain peaks, that is, the temperature inside the bags rises with the increase of outside temperature, but the time when it reaches its peak varies according to different years, seasons and types of paper bags. Within a single day, the temperature is lowest at about 5:00, and after 9:00 it rises sharply, reaching its peak in early and late stages usually at 13:00—14:00 and in hot summer usually at 13:00—17:00; humidity inside the bags has a negative correlation with temperature, changing in V shape with maximum humidity at about 6:00.2. Under high temperature, the change curves of temperature and humidity in different bags are significantly different. As atmospheric temperature is above 30℃, temperature inside the paper bags rises sharply, while humidity declines in the same manner. Duration of being above 38℃inside the Xiaolin bag amounts to 34 hours, in single-layer paper bag 29 hours and in Huang Wen bag 21 hours; extreme dryness inside bags under high temperature is another noticeable phenomenon, and when temperature inside bags is above 35℃, relative humidity is usually below 40%. Accumulated hours of relative humidity being lower than 60% reach 207～227 h, and among them single-layer bag has the most accumulated hours of being less than 40% say 56h, Huangwen has the least 37h and Xiaolin and Kaixiang stand in the middle; under extreme dry conditions, relative humidity in all the bags is 18.8%～22.6%.3. In rainy days, temperature and humidity in different paper bags are similar, with relatively low temperature and decreasing diurnal amplitude. Most of the rain water filters into the bags, and duration of sustained high humidity inside the bags is obviously longer than that of raining; among all the bags, single-layer bags have a longer duration of sustained high humidity than that of double-layer bags.≥90% accumulated hours in single-layer bags reach 576 hours, among which Xiaolin bag has most accumulated hours of sustained high humidity say 565 hours.4. The selection of bags has an important effect on fruit appearance quality and double-layer bags perform better in improving fruit appearance quality. Fruit developing inside Xiaolin bags has the highest appearance quality, with 44% first-rate fruit. Huiyang is second and Shuangbao is worst with 34% first-rate fruit. The fruit developing in single-layer paper bags and reflection bags is relatively bad, with more black-dot disease and rust disease and first rate fruit is less than 21%. Damage rates of different paper bags after wind and rain are significantly different. Xiaolin is best with a damage rate of only 2%, Kaixiang second, and Shuangbao suffers little damage but many clefts. Damage rates of Qingtian and Fenghua are highest say 22% and 14% respectively.5. Influence of bagging on illumination on tree canopy. The 3-5 leaves clinging to the bagged fruit cannot reach any light, and their photosynthetic rate is below zero; the inner bore and under-layer of a bagged tree are affected, and their relative light intensity are reduced to 72.7% and 63.6% respectively; trees with high stem and open center shape or small and sparse canopy shape are affected most greatly by bagging, their relative light intensity at 50cm are reduced to 54.1% and 45.5% respectively.6. Due to their different structures, different tree shapes have different rules of 3D light distribution. Trees with high stem and open center shape have fewer canopy layers, so transmitting coefficient of the direct light is high and extinction coefficient is low. The light intensity at the lower part of the tree is 45.1%; Trees with big canopy and densely planted spindled-shape tree has lowest transmission coefficient for solar radiation penetration and extinction coefficient is as high as 0.94～1.1. Light intensity within the canopy is poor, The light intensity at the lower part of the tree is 27.9% and 24.7%,and the leaves'photosynthetic rate is negative . Generally speaking, illumination level and light energy utilization of small canopy trees is obviously better than that of big canopy trees; trees with high stem are better than trees with low stem.