Study On Citrus Leaves Photosynthetic Rate Models In Response To The Environmental Factors And Effects Of Arbuscular Mycorrhizal Fungi On Photosynthesis Characteristics

The citrus is a member of Citrus Linn of Rutaceae. The fruit of citrus is delicious, rich in nutrient and can be eaten raw, which also can be processed into kinds of production including juice. The citrus plants are high and stable yield, so they can create high economic value, which have become the most important fruit trees in the south of China. They play a significant role in developing rural economy.It is considered that Chongqing is one of the three major places of citrus production in China, however, according to the characteristics of climate and climate data in Chongqing, it is showed that during the summer (May-August), the environmental conditions are high temperature, drought, sufficient sunshine; and in fall and winter season (September-December) it often has "little" sunshine. Photosynthesis is the most important chemical reaction on Earth, which is not only the source of all matter and energy, but also the basis of the quality formation and the production of citrus. Environment is an important factor in restriction of photosynthesis. In order to improve photosynthesis and increase yield and quality in citrus, it is great significant to in-depth understand how environmental factors regulate photosynthesis of physiology and mechanism. In this paper, under the Chongqing "special" climatic conditions in different periods, we established a photosynthetic rate model to study the major environmental factors which affected the capacity of citrus photosynthesis most and its mechanism of action. We also answered the problem that whether to inoculate AMF could improve and enhance the capacity of photosynthesis at different P levels in citrus. The results are as follows:Experiment 1: The research for citrus leaves photosynthetic rate models in response to the environmental factorsThe experiment used Wmurcott (Citrus reticulata Blanco×Citrus sinensis Osb. cv. Murcott) as the materials, under conditions of early summer (May, June), summer (July, August) ,autumn (September, October) and winter (November, December) in Chongqing , according to Monsi and Saekit of the rectangular hyperbolic equation of single-leaf photosynthetic rate of photosynthetic active radiation response equation and Jarvis P.G leaf stomata conductance model and the relationship between environmental factors (referred to as Jarvis model),we have measured photosynthetic physiological characteristics of citrus leaves (photosynthetic active radiation, stomata conductance, leaf temperature, atmospheric CO₂ concentration) with LX-6400 portable photosynthetic apparatus to establish citrus leaves photosynthetic rate models in response to the environmental factors in Chongqing. The results are as follows:As we can see from different months or from periods the citrus leaf-scale photosynthetic rate in Chongqing, the environment variables must be greater than 3. Observation data from the environmental group variables on citrus leaf photosynthesis rate show the influence degree of accuracy followed by (photosynthetic active radiation) PAR > stomata conductance > leaf temperature > atmospheric CO₂ concentration. Environmental variables in the models influenced the accuracy of the performance not only a single environmental variable but also the interaction among variables. In the models, PAR and stomata conductance are basic two environmental variables, at the some time, including the leaf temperature or atmospheric CO₂ concentration (one or two) environmental variable(s); In this period of Chongqing in early summer (May, June), citrus leaves photosynthetic rate in response to the environmental models may be in the form of P (G)^*P(A)^* P (T). In this period of Chongqing in autumn (September, October), the environmental models may be the in the form of P (G)^* P (A)^* P (C). And in this period of Chongqing in summer (July, August), winter (November, December) and half the year (May- December)citrus leaves photosynthetic rate in response to the environmental models may be the in the form of P(G)^* P(A)^* P(T)^* P (C).Experiment 2: The research for citrus leaves photosynthesis characteristics at different P levels AMF inoculationThe experiment was conducted with Wmurcott (Citrus reticulata Blanco×Citrus sinensis Osb. cv. Murcott) as materials. AM species are Glomus mosseae spores. Through Clover to mycorrhizal rhizosphere soil for the vaccination after propagation, they were inoculated in the soil of pot. The experiment has 6 treatments (P level of inoculation, P levels; low P level of inoculation, low P levels; high P level of inoculation, high P levels). After AMF inoculation, in May, July, September and November respectively, we have measured photosynthetic physiological characteristics of citrus leaves with LX-6400 portable photosynthetic apparatus and (listed marker on the same shoot) took some materials for analysis. The results are as follows:In May, July, September and November in Chongqing, the research for citrus leaves photosynthesis characteristics of AMF mycorrhizal inoculation at different P levels showed that: whether it was adequate in the sunshine in May and July, or in the "little sunshine" in September and in November, vaccination at different levels of P levels, compared to non-inoculated AMF, could significantly improve the physiological and biochemical indexes of chlorophyll content of citrus leaves and leaf P utilization of light and dry weight content, the leaf photosynthetic products (protein, soluble sugar) content. And at this period, vaccination could prevent photosynthesis reducing. And through improving the stomata conductance, it also could improve the photosynthetic rate; after inoculation, mycorrhizal infection accompany with the deepening of the root system also enhanced Peroxidase activity. Peroxidase activity of roots and root mycorrhizal infection rate was very significant positive correlation, and it showed that mycorrhizal citrus root formation and development could effectively promote the physiological metabolism of citrus roots, thereby enhanced the activity of root system to improve photosynthesis, promoting the plants on soil P absorption and increasing the dry weight of leaf P content. It was not significant to apply P alone (at this P levels treatments of the paper) for photosynthesis of citrus leaf. In mycorrhizal citrus and other host plants of the effects of photosynthesis, AMF could enhance the photosynthesis of infection of citrus leaf and the effects of infection were itself so as to improve the absorption of the P not but the application of P. In Chongqing "special" climate, it is a simple technology and easy way for citrus seedlings to improve the photosynthesis by inoculating AMF.