Effects Of Light Intensity On Physiological Indexes And Fruit Quality Of ‘Wen 185' Walnut

Walnut is a kind of tall tree and closely cultivated species in agricultural production,and it shades seriously among tree body.Our aim is to explore the effects of severe shading on walnut trees.‘Wen 185'walnut cultivar was selected as the test material and white nylon mesh was used to artificial simulate shade in the walnut Hardcore phase.In addition,different gradients for light treatments were also set in order to research the effects of different light treatments on physiological and biochemical indexes,leaf anatomical structure,photosynthetic fluorescence characteristics,fruit quality and yield of walnut leaves.Our paper aims to figure out the reasonable and effective cultivation management measures by studying different light environments to provide the basis for arborescent close planting pattern and pruning of‘Wen 185'walnut finally.The results are as follows:(1)During the hard phase,the chlorophyll content is high under the treatment of 43% light transmittance,and after filling period,the chlorophyll content marks a low level under treatment of 43%light transmittance,while the treatment of 84% light transmittance marks higher level.Hence,the results showed that short duration,heavy and time heavy shading could improve chlorophyll content.At the moment,light transmittance is 84% can help anatomical structure of the leaves to promote the growth of walnut through improving the thickness of spongy tissue,epidermal cell length,palisade tissue / spongy tissue,stomatal length and stomatal area.Compared with full sunlight,light transmittance is 43% increased the chlorophyll content by 0.913 mg·g-1 in a short time and reached the significant level.But when light transmittance is lower than 69%,it is not conducive to the accumulation of photosynthetic products or improves stress resistance of walnut tree which highlights the chlorophyll and proline content decreased,while MDA content increased.In addition,leaf potential and area of walnut leaf under shading treatment are higher than the full exposure but it will reduce the weight of single leaf.(2)During the oil conversion period,84% light treatment can improve the stomatal conductance(Gs),intercellular C02 concentration(Ci)and transpiration rate(Tr),they were increased 0.016 mol·m-2·s-1,35.25?mol·mol-1,0.95 mmol·m-2·s-1 respectively compare with 100% translucent treatment.Severe shading can reduce the net photosynthetic rate,stomatal conductance and transpiration rate,and were reduced 6.01?mol·m-2·s-1,0.064 mol·m-2·s-1,3.15 mmol·m-2·s-1 respectively.At the same time,shading can reduceinitial fluorescence(F0),increase the maximum fluorescence(Fm),primary conversion of light energy of photo-system ?Quantum yield of photosynthesis,photo-chemical and non-photo chemical chlorophyll fluorescence to avoid high temperature and strong light stress on walnut production.(3)From the beginning of short duration shade,the vertical diameterof nut,single fruit weight,kernel rate,protein content and yield were 39.43 mm,13.88 g,69%,2.806 mg·g-1 and 4159 kg·hm-2 respectively under 84% translucent treatment,and significantly higher than other light intensity treatments.Under 43%translucent treatment the crude fat,reducing suger and hard shell thickness increased by 8%,0.127 mg·g-1,2.66 mm respectively compares with 100% transmittance.At the moment,43% translucent treatment reduced fruit taste and increased fruit lignification and astringency because cellulose,tannin and total polyphenol content of walnut nuts had risen.Shading can improve organic acid,soluble sugar and fatty acid content in walnut kernels,but there was no significant correlation between different light conditions.