Differences in Light Response Curve and CO_2 Response Curve of Korla Fragrant Pear Trees in Different Training Systems

[Objective] This study was conducted to evaluate three training systems for Korla fragrant pear trees by comparing the characteristic parameters of light response curve and CO2 response curve, and to provide some theoretical basis for improving the pruning techniques of Korla fragrant pear trees. [Method] The light response curve and CO2 response curve of the trees trained to three systems were measured by LI-6400 portable photosynthesis system. The SPAD value was measured using SPAD-502 chlorophyll meter, and specific leaf weight was calculated, to evaluate the effects of the three training systems. [Result] The CO2 response curves of the three training systems were basically in agreement with their light response curves, but there were some differences in their characteristic parameters. Among the three training systems, the maximum net photosynthetic rate, apparent quantum yield and light compensation point of espalier trained trees were the highest, while their light saturation point was the lowest. The CO2 saturation point of delayed-open central leader trained trees and open center trained trees were 1 752 and 1 665 μmol/mol, both of which were much higher than that of espalier trained trees. In addition, the carboxylation efficiency and photorespiration rate of espalier trained trees were both higher than those of delayed-open central leader trained trees and open center trained trees, while the CO2 compensation point of espalier trained trees was the lowest. The leaf SPAD value of espalier trained trees was the largest, followed by that of open center trained trees, and the leaf SPAD value of delayed-open central leader trained trees was the smallest. In addition, the leaf area and specific leaf weight of espalier trained trees were both the highest, followed by those of open center trained trees. [Conclusion] Among the training systems for Korla fragrant pear trees, the espalier training system had better ability to capture light, higher photosynthetic productivity and strongest adaptability to light environment, and open center training system takes the second place. On the contrary, delayed-open central leader training system has the weakest adaptability to light environment, but it can adapt to a higher CO2 concentration. In summary, for the training of Korla fragrant pear trees, espalier training system, which has the highest theoretical yield, is the best among the three training systems, and delayed-open central leader training system is the worst.

Responses of Phytolith in Guinea Grass(Leymus chinensis) Leaves to Simulated Warming,Nitrogen Deposition and Elevated CO_2 Concentration in Songnen Grassland,Northeast China

Deposited in plant cells and their intercellular space,phytoliths,a special form of silica,could be used to determine information on plant structure and physiology especially their size and content.With the hypothesis that phytolith in plant would change under variable climate and environment,the dominant plant species in Songnen grassland,guinea grass(Leymus chinensis),was treated by an open-top chamber(OTC) to elevate CO2 concentration,infrared heaters,and artificial nitrogen(N) addition for three years from 2006–2008.Phytoliths were extracted by wet-ashing method and analyzed by variance analysis and so on.We found that the responses to elevated CO2 are complicated,and warming is positive while N addition is negative to the deposition of phytoliths in L.chinensis leaves.Especially,warming could reduce the negative impact of N addition on phytolith in L.chinensis.The short cell's taxonomic in graminea is significant because of no disappearance with simulated environmental changes.The phytolith originated in the long cell and plant intercellular space are more sensitive to elevated CO2 concentration,warming,and N addition,and could become some new indicators for environmental changes.In conclusion,different phytolith types have various responses to simulated warming,N addition and elevated CO2 concentration.

Differences of Photosynthetic Characteristics of the Grape Cultivated in Greenhouse and Open Field in Turpan

[Objective] This study compared the leaf photosynthetic characteristics of Turpan grape cultivated in greenhouses and open field to provide a scientific basis for the high-quality and high-yield cultivation of grape. [Method] Two precocious grape varieties as experimental materials were cultivated in greenhouses and open field, and their net photosynthetic rates （Pn）, photo-response curves and CO2 response curves were determined using Li-400XT portable photosynthesis system. [Result] The leaf Pn of the two varieties cultivated in open field was higher than that in greenhouse. The Pn of Hongqitezao cultivated in open field was the highest, up to 19.79 μmol/（m^2·s）; in the photo-response curves, Hongqitezao cultivated in greenhouse had the largest Pnmax and apparent quantum yield （AQY）, while the Flame Seedless in greenhouse had the smallest light compensation point （LCP）. The light saturation point （LSP） value of greenhouse cultivation was higher than that of open field cultivation. In the CO2 response test, the dark respiration rate （Rd） and Pnmax of greenhouse cultivation were higher than those of open field cultivation, and the carboxylation efficiency （CE） of greenhouse cultivation was lower than that of open field cultivation; the CO2 compensation point （CCP） and CO2 saturation point （CSP） of greenhouse cultivation were lower than those of open field cultivation. [Conclusion] The utilization of elevated light in greenhouse cultivation was more efficient than in open field cultivation; however, the utilization of elevated CO2 in greenhouse cultivation was weaker than tin open field cultivation.

Comparison of Photosynthetic Characteristics among Different Prunus domestica × armeniaca Cultivars

[Objective] This study aimed to investigate the photosynthetic characteristics of different Prunus domestica × armeniaca cultivars, thereby providing some theoretical basis for high-yield and high-quality cultivation of P. domestica × armeniaca. [Method] Total three cultivars（Konglongdan, Fengwei Huanghou and Weiwang）of P. domestica × armeniaca were selected as the test materials, and their leafphotosynthetic parameters were measured with Li-6400 portable photosynthesis system.The light response curve and CO_2 response curve were drawn. [Result] There were significant differences in photosynthetic rate among the three cultivars of P. domestica × armeniaca（P〈0.01）. The photosynthetic rate of Konglongdan [14.76 μmol/（m^2·s）]was highest. When the light intensity reached 1 800 μmol/（m^2·s）, the maximum net photosynthetic rate of Konglongdan was up to 27.27 μmol/（m^2·s）, and its apparent quantum yield reached the peak. Konglongdan showed lower light compensation point [43.069 μmol/（m^2·s）] and higher light saturation point [697.684 μmol/（m^2·s）].Weiwang showed the lowest CO2 compensation point（68.264 μmol/mol） and the highest carboxylic efficiency [0.072 μmol/（m^2·s）]. [Conclusion] Konglongdan showed the highest light utilization efficiency and photosynthetic potential, and it had the strongest utilization ability for weak light. The utilization ability of Weiwang for lowconcentration CO2 was strongest, followed by those of Fengwei Huanghou and Konglongdan.

Response of soil CO_2 efflux to precipitation manipulation in a semiarid grassland

Soil CO_2efflux（SCE） is an important component of ecosystem CO_2 exchange and is largely temperature and moisture dependent, providing feedback between C cycling and the climate system. We used a precipitation manipulation experiment to examine the effects of precipitation treatment on SCE and its dependences on soil temperature and moisture in a semiarid grassland. Precipitation manipulation included ambient precipitation, decreased precipitation（- 43%）, or increased precipitation（＋ 17%）. The SCE was measured from July2013 to December 2014, and CO_2 emission during the experimental period was assessed.The response curves of SCE to soil temperature and moisture were analyzed to determine whether the dependence of SCE on soil temperature or moisture varied with precipitation manipulation. The SCE significantly varied seasonally but was not affected by precipitation treatments regardless of season. Increasing precipitation resulted in an upward shift of SCE–temperature response curves and rightward shift of SCE–moisture response curves,while decreasing precipitation resulted in opposite shifts of such response curves. These shifts in the SCE response curves suggested that increasing precipitation strengthened the dependence of SCE on temperature or moisture, and decreasing precipitation weakened such dependences. Such shifts affected the predictions in soil CO_2 emissions for different precipitation treatments. When considering such shifts, decreasing or increasing precipitation resulted in 43 or 75% less change, respectively, in CO_2 emission compared with changes in emissions predicted without considering such shifts. Furthermore, the effects of shifts in SCE response curves on CO_2 emission prediction were greater during the growing than the non-growing season.