Studies On Photosynthetic Physiology And Carbon Substance Metabolism In 'Hanfu'Apple

The breeding of 'Hanfu' apple played an important role for expanding the cultivation area and building the new superior industry belt of big fruit apple,but the researches of related physiological basis and the mechanism of technical measures are great shortage. Particularly,the researches on effects of cold weather conditions on related physiological basis of high-quality and big fruit apple has not been reported.In this paper,with 'Hanfu' apple and its parents 'Dongguang' and 'Fuji' apple as the materials,the photosynthetic physiology and carbon material metabolism of 'Hanfu' apple were evaluated preliminarily by the means of photosynthetic gas exchange and chlorophyll fluorescence analysis combining with tissue anatomy characteristic analysis and physiological and biochemical detection.The photosynthetic physiological and carbon material metabolism basis of 'Hanfu' apple under the conditions of a variety of stress,different soil management systems were studied for discussing the mechanism of photosynthetic physiological and carbon material metabolism, revealing the physiological basis of multiple resistance expression of 'Hanfu' apple in cold regions and providing a theoretical basis for high-quality cultivations and managements of 'Hanfu' apple in cold regions.The main results were as follows:1 Compared with that of 'Dongguang' and 'Fuji'apple,the leaves of 'Hanfu' apple had higher thickness of mesophyll and the largest rate of palisade tissue and spongy tissue.The stomatal density,grana thickness,number of grana lamellae and specific lamella number of granum were significantly higher than its parents.The photosynthetic capacity,apparent quantum yield,carboxylation efficiency and maximum regeneration velocity of RuBP, chlorophyll content and specific leaf weight were higher than its parents.The leaves of 'Hanfu' apple had higher initial fluorescence,lower maximum fluorescence yield, PSâ…¡maximum photochemical efficiency and performance index.The photosynthesis starting time of leaves in 'Hanfu' apple was shorter and the maximum(19.5μmol·m^-2·s^-1) was appeared at about 22 minutes.'Hanfu' apple had a higher saturation light intensity,Saturation CO₂,CO₂ compensation point and lower light compensation point,which respectively were (1665±20)μmol·m^-2.s^-1,(2961±41)μmol·mol^-1,(87.5±1.4)μmol·mol^-1,and (5.9±1.8)μmol·m^-2·s^-1.During annual growth cycle,the eontents of soluble sugar and starch in 'Hanfu' apple were slightly lower than that of 'Dongguang' apple leaves,but significantly higher than that of 'Fuji' apple leaves.2 The photosynthetic physiological parameters of different developmental leaves were different.The photosynthesis starting time of functional and young leaves were shorter start photosynthesis,the maximum(19.5μmol·m^-2·s^-1 and 12.29μmol·m^-2·s^-1) were appeared at about 22 minutes.The apparent quantum efficiency and stomatal limitation value of functional leaves were significantly higher than that of young leaves and senescence leaf.The photosynthetic capacity of functional leaves and young leaves was no significant difference, but both were significantly higher than senescence leaf.The carboxylation efficiency and RuBP maximumn regeneration rate of leaves at different developmental stageshad no difference.The saturation light intensity,light compensation point and saturation CO₂ of functional leaves were higher than that of young leaves and senescence leaves whereas the CO₂ compensation points was lower,which respectively were(2210±10.6)μmol·m^-2·s^-1, (28.5±2.8)μmol·m^-2·s^-1,(1222.7±42)μmol·mol^-1,and(85.6±1.5)μmol·mol^-1.All showed that the functional leaves and the capacity of using high light,high and low CO₂.With the development of leaves,the net photosynthetic rate gradually increased,it reached the peak after leaf maturation and decreased rapidly with the aging of leaves.The soluble sugar contents of leaves were higher at the early stage of development,which decreased with the flowering and rapid growth of new shoots.After new shoots stopped growth,the soluble sugar and starch content reached peaks,which decreased with leaf senescence.During the annual growth cycle,the glucose and sorbitol content(44.587mg·ml^-1 and 32.287mg·ml^-1) was significantly higher than that of sucrose and fructose content(3.841mg·ml^-1 and 2.333mg·ml^-1) in 'Hanfu' apple.3 The nutrient content of different types of tissues,organs and branches were different in 'Hanfu' apple.The soluble sugar content in leaves was the highest,and the starch content in phloem was the highest.The soluble sugar content in leaves,the soluble sugar and starch content in xylem of autumn shoots were higher than that of spring shoots and one-year-old top-cutting shoots.During the process of nutrient redistribution,the starch content in the one-year-old branch phloem and xylem,the soluble sugar in one-year-old branch xylem were the highest,and the soluble sugar content in trunk phloem was the highest. 4 The photosynthetic physiological parameters of leaves at different leaf node in 'Hanfu' apple were different.The net photosynthetic rate showed the trend of from low to high.The Pn of basal leaves was lower,it maintained a fairly high level from the base fourth node,and the difference among the nodes was smaller.The leaves at the 11th to 16th nodes had lower initial fluorescence and maximal fluorescence yield,the PSâ…¡maximumn photochemical efficiency and performance index were higher than that of leaves at the base and tip of shoot.5 Under planting and covering grass treatment,the thickness of leaves,palisade tissue and the rate of palisade tissue and spongy tissue,the stomatal density,the number of chloroplasts,chloroplast length,number of grana lamellae and specific lamella number of granum increased to some extent.The granum-thylakoid were arranged compactly and regularly with developed chloroplast lamellar structure.The photosynthetic pigment content, the net photosynthetic rate,the initial fluorescence,maximal fluorescence yield and the performance index improved.The soluble sugar and starch content of leaves,phloem and xylem increased.6 Under low-light stress,the thickness of leaves and spongy tissue were thinned with loose palisade tissue,the rate of palisade tissue and spongy tissue and basal granule thickness increased.The size of chloroplast was significantly smaller,the number of grana lamellae and specific lamella number of granum decreased,the chloroplast grana lamellae structure was thickened,the lamellar gap was enlarged and a large number of plastoglobuli appeared. Under low light stress,the net photosynthetic rate,water use efficiency and stomatal conductance were reduced,and PSâ…¡conversion efficiency of primary light energy and the potential activity of PSâ…¡improved.The photosynthetic capacity,apparent quantum yield, carboxylation efficiency,stomatal limitation value and the RuBP maximum regeneration rate, saturation light intensity,light compensation point and saturation CO₂ decreased with the weakness of light intensity,but the CO₂ compensation points increased.After the 'Hanfu' apple leaves constructed in low light transferred to the strong light suddenly,the photosynthesis starting time was prolonged.The soluble sugar content increased,the activity of sucrose phosphate synthase enhanced,but the activity of glutamine synthetase,invertase, sorbitol dehydrogenase and sorbitol oxidase declined,the activity of sucrose synthase maintained stability,which indicated that 'Hanfu' apple was a photophil and shade-tolerant plants. 7 Under light drought stress,the thickness of palisade tissue and the rate of palisade tissue and spongy tissue increased.A layer of inactivated phellem tissue appeared on the upper epidermis and the inactivation point appeared in the palisade tissue cells.In moderate and high drought stress and waterlogging conditions,the palisade tissue and spongy tissue cells in mesophyll disintegrated,a lot of broken cells and cavity appeared,and the proportion of xylem increased.Under moderate water stress,the stomatal conductance,water use efficiency increased and PSâ…¡conversion efficiency of primary light energy and the potential activity of PSâ…¡improved,but the net photosynthetic rate had no effect.With the heavier of stress levels,the photosynthetic parameters and chlorophyll fluorescence parameters of 'Hanfu' apple had be affected irreversibly.In water stress conditions,the soluble sugar content increased,and the starch content reduced.The heavier of stress,the greater of change range.Under light drought stress,the neutral invertase,acid invertase and sucrose synthase activity improved,sucrose phosphate synthase,sorbitol dehydrogenase,sorbitol oxidase and glutamine synthetase activity reduced.In moderate and high drought stress and waterlogging conditions,neutral invertase,acid invertase and sucrose synthase activity reduced enhanced. 'hanfu' apple was a cultivar with strong drought resistance because it could tolerate light and moderate drought.8 Under high humidity stress,the thickness of leaves and palisade tissue cells markedly increased.The structure of spongy tissue was damaged,mesophyll cells was disintegrated,a large number of cavity and inactivation point appeared.The net photosynthetic rate, PSâ…¡conversion efficiency of primary light energy and the potential activity of PSâ…¡reduced and the initial fluorescence yield increased,but the distribution of energy did not significantly be affected.The soluble sugar increased and starch contents decreased.The neutral invertase, acid invertase,sucrose synthase and glutamine synthetase activity improved,sucrose phosphate synthase,sorbitol dehydrogenase,sorbitol oxidase activity reduced.'hanfu' apple was a cultivar with strong high humidity resistance.