| Jujube tree is an important economic species. In recent years, the Jujube industry has been developed rapidly, the current cultivated area has more than 1,000,000 square meters. With the scope of the cultivation area and the rapid expansion, a large number of seedlings are be needed from the garden through digging seedling, grading, original packaging, wintering, storage and long-distance transporting to afforestation, Jujube seedlings suffered many factors of stressing, which results a low survival rate and prophase growth. Therefore, study on physiological responses under transplanting stress on Jujube seedling and explore physiological influence under transplanting stress on seedlings and finding survival and resume growth mechanise of stransplanting seedlings can enrich theory of silviculture and provide theory foundation of enhancing sylvicultural effects.One-year-old Jujube seedlings was used in this experiments as materials, through different degree of stressing, simulated of the production process of planting, laws of water content, SOD activity, soluble protein content, soluble sugar content, MDA content content, photosynthetic, chlorophyll fluorescence parameters, transpiration and prophase growth were studied and discussed the physiological responses under transplanting stress on Jujube seedlings. on this basis, physiological foundation of antitranspirant alleviating tress on seedlings also were systemic studied,The main conclusions were as follows:(1) Transplanting stress had a significant effect on the water situation. Transplanting accelerated seedling water loss. The greater stress intensity was, the higher the seedlings water loss rate was. Root water loss rate was higher than the stem’. Stress time were designed by 12h,24h,36h and 48h and stem water loss rate was 5.68%,7.46%,8.61% and 9.99%, while root water loss rate was 16.83%, 27.02%,33.80% and 38.86%, respectively. The differences were obvious among different stress. There was a significant negative correlation between seedling water loss rate and transplanting survival rate. The correlation coefficient were 0.9177 between stem water loss rate and transplanting survival rate, while 0.8979 between root water loss rate and transplanting survival rate in transplanting 90d. According to the established regression equation, if transplanting survival rate was more than 40% in 90d, stem and root water loss rate’threshold was 9.63% and 35.57%,respectively. Or else, seedling was difficult to survive. The appropriate interval between transplanted and planted was no more than 36h,24h in the best control.(2) After seedling was transplanted, different part water content trends was different. Seedling stem water content had a "down to up to stable" trend. In transplanting 0-5d, stem water content from 26.7% to 36.0% dropped from 23.9% to 30.1%.In 60d, stem water content rose from 41.9% to 42.5% and then it was gradually stabilized from 42% to 47%. Root water content had a "up to stable" trend. In transplanting 0-20d, root water content from 27.2% to 39.0% rose from 42.5% to 44.6%, followed stabilized at the level from 44% to 54%.(3) After seedling was stressed by transplanting, stem SOD activity had a "up to down to stable" trend. In transplanting 0-5d, SOD activity from 152.3 to 177.2U/g rose from 158.9 to 190.3U/g. In transplanting 45d, it dropped to the level from 132.3 to 136.3U/g. SOD activity was identical with left seedling’, after this it was stabilized at the level from 129 to 133U/g.(4) During seedling transplanting survival, stem soluble protein content had a "down to up to stable" trend. In transplanting 0-5d, stem soluble protein content from 21.39 to 26.61mg/g dropped from 13.90 to 22.33mg/g. In transplanting 45d, it rose to the level from 24.16 to 26.11mg/g. Stem soluble protein was basically identical with left seedling’, after this it was stabilized at the level from 25 to 28mg/g.(5) After seedling transplanted and planted, stem soluble protein content had a "up to down to stable" trend. In transplanting 0-5d, stem soluble protein content from 17.66 to 21.15mg/g rose from 18.39 to 21.87mg/g. In transplanting 45d, it dropped to the level from 14.51 to 15.58mg/g. Stem soluble protein content was basically identical with the seedling’, after this it was stabilized at the level from 14 to 15mg/g.(6) After seedling transplanted, stem MDA content had a "up to down to stable" trend. In transplanting 0-10d, stem MDA content from 21.1 to 25.5mg/g rose from 25.0 to 35.4mg/g. In transplanting 60d, it dropped to the level from 20.0 to 20.8mg/g. Stem MDA content was basically identical with left seedling’, after this it was stabilized at the level from 20 to 21mg/g.(7) Transplanting stress had a significant effect on Jujube seedling photosynthesis and transpiration. With different disposal level, net photosynthetic rate (Pn), transpiration rate (Tr), water use efficiency (WUE) and stomatal conductance (Gs) had an evident differences in the day changes. After transplanting, left seedling and stress over 12h, all the parameters changes were double-peak curve. The first peak was at 11 o’clock and the second peak at 15 o’clock in the afternoon. There was a "lunch" phenomenon. Stress over 24h including 24h, the day change was single peak-curve, the second peak disappeared. After seedling was stressed, transpiration and stomatal conductance reduced which affected leaf gas transmission and caused photosynthesis to drop. If seedling was stressed by 48h,Tr, Gs, Pn was decreased by 30.8%,47.5%,40.0% than left seedling’, respectively.(8) Seasonal variation of Jujube seedling photosynthesis and transpiration were double-peak curve. In June and September there were two peaks and the second peak was lower than the first. Throughout the growing season, in different stress disposal level, Pn, Tr that were lower than left seedling. The greater transplanting stress was, the lower Pn, Tr was. In June, stress 48h, Pn and was decreased by 43.2%,52.7% than left seedling, respectively.(9) Transplanting stress had a significant impact on Jujube seedling fluorescence parameters. After transplanting, Jujube seedling leaves initial fluorescence (Fo). the largest fluorescence (Fm) and the variable fluorescence (Fv) were lower than left seedling. Fv/Fm and Fv/Fo) were both lower than left seedling. The longer Jujube seedling transplanted was, the more obvious differences were. When seedling was stressed by 48h, Fo, Fm and Fv was 29.2%,17.2% and 14.8% higher than left seedling, while Fv/Fm and Fv/Fo was decreased by 2.1% and 11.5%. Transplanting stress restrained normal photosynthesis and resulted in a corresponding fluorescence parameters change.(10) Transplanting stress slowed the seedlings growth. The greater the stress intensity was, the smalle seedling growth was. The main effects of transplanting stress on the height and diameter was taken place in three months. Seedling height and diameter had a significant difference in different stress time. The growth difference was no evident in 3 months. Stress 48h, from April to June, height increment were reduced by 61.67%,58.46%,64.19% while diameter increment were reduced by 48.28%,47.67% and 37.50%, respectively.(11) Antitranspirant had a significant restraining effect on water loss during transplanting seedlings was stressed. With antitranspirant spraying, stem and root seedling water loss rate was less than non-spraying. With spraying concentration increasing, restraining effect was enhanced. Stress 12h, spraying 100ml.L-1 antitranspirant, root water loss was 8.33% lower than non-spraying. Stem water loss rate was reduced by 4.01%. To a certain extent, spraying antitranspirant could be offset by transplanting seedling stress on water loss.(12) Antitranspirant spraying significantly affected transplanted seedling water situation. With antitranspirant spraying, within 15d, stem and root water content was higher than without antitranspirant. With spraying concentration increasing, seedling water content was enhanced. In transplanting 0,5,15 and 20d, spraying 100ml.L-1 antitranspirant, root system water content was 4.48%,5.61%,7.45% and 6.72% higher than seedling without it, while stem water content were 4.93%,3.96%,6.14% and 4.59% higher than seedling without it, respectively.(13) Antitranspirant had a significant impact on survival rate of transplanted seedling. Seedling of antitranspirant sprayed, transplant survival rate was higher than without antitranspirant in transplanting 120d, but there was not a positive correlation between antitranspirant concentration and seedling survival rate. The highest seedling survival rate was 94.3% with spraying concentration 50ml.L-1 while survival rate decreased to 86.5% with spraying concentration 100ml.L-1 antitranspirant.(14) Spraying antitranspirant had an impact on Jujube seedling SOD activity. In transplanting from Od to 10d, seedling of antitranspiran sprayed, SOD activity change range reduced than without spraying it. In 10d, seedling SOD activity was enhanced comparing with non-spraying. Antitranspirant increased seedling resistance. Concentration 50ml.L-1 was the most effective. Its change range was 32.6 U/g (from 135.7 to 168.3 U/g) that decreased 75.28% comparing with non-spraying change range 131.9U/g (from 85.6 to 217.5 U/g).(15) Antitranspirant spraying increased transplanted seedling soluble protein content. Antitranspirant restrained depressed trend of 0-10d transplanted seedling soluble protein content. In 10d, antitranspirant sprayed seedling, soluble protein content was still higher than non-spraying seedling and seedling resistance was increased.50ml.L-1 concentration was the best. Average content was 21.12mg/g that increased by 16.58% comparing with non-spraying.(16) Antitranspirant spraying increased transplanted seedling soluble protein content. Transplanting seedling of antitranspirant sprayed, soluble sugar content was higher than non-spraying during different period. Antitranspirant enhanced seedling osmotic adjustment ability. 100ml.L-1 concentration was the best. Average content was 18.28mg/g and 13.76% was increased comparing with non-spraying (17) Different antitranspirant spraying concentrations had different impacts on transplanted seedling MDA content. With 25 and 50ml.L-1, transplanted seedling MDA content was not lower than non-spraying. With 100ml.L-1, MDA content was higher than non-spraying. Aappropriate antitranspirant concentration was favorable to membranaceous permeability. 50ml.L-1 was the best. Average content was 25.39μmol/g and 11.12% was decreased comparing with non-spraying.(18) Antitranspirant spraying had no evident impact on transplanted seedling Pn and Tr. Different antitranspirant spraying did not change Pn and Tr day law. With 25 and 100ml.L-1, Pn and Tr was lower than non-spraying while 50ml.L-1 was higher. Different disposal was not a significant level.(19) Different antitranspirant spraying concentrations had different impacts on transplanted seedling increment.25 and 50ml.L-1 increased transplanted Jujube seedling height and diameter. Growth was reduced with 100ml.L-1. 50ml.L-1 had the most significant promotion on the growth, and in 180d, height and diameter increased by 16.44% and 17.14% compared with non-spraying, respectively.(20) Antitranspirant reduced seedling water loss and then improved infiltration conditions, raised seedling resistance, ect, and effectively reduced adverse effects of transplanting stress, and increased transplanted seedling survival rate, and promoted seedling growth. The results of functions comprehensive analysis shown that 50ml.L-1 was the best for transplanted seedling. Comprehensive value was 0.272 and was 7.77 times than non-spraying seedling (0.035).In the process of seedling transplanting, there was excavating seedling, transportation, grading, packing, storage, temporary planting, then transportation again, eventually planted. In the period, there was some factors such as cutting, water loss, abrasion, vibration, heat or cold, light cycle disorders, inadequate light, lack of oxygen, water-logging, pests, toxic substances, changes in rhizosphere abnormal, ect. If seedling was stressed by one or more the listed factor and planted to cause death or abnormal growth. One reason was that transplanting stress continued to play a role, on the other hand, some afforestation conditions could be not suitable for seedling growth and development and also be a new stress. The process was a multi-factor, uncontrollable, longtime and was an integrated stress state. The process could not be a factor or a certain period to be represented. Therefore the concept of transplanting stress was brought forth in this paper. Based on seedling physiological and biochemical changes index, the process of seedling survival or restoration growth was divided into tolerance, stability and recovery three time. To Jujube seedling, tolerance time was from 5 to 10d, and recovering time was from 11 to 60d, and in 60d it was stability time... |
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