Research Of Different Cotton’s Photosynthetic Characteristics And Photoprotection Mechanisms In Field

Objective: In southern Xinjiang unique natural conditions the light temperature and drought stress is themain environmental factors may exacerbate plant photoinhibition. In this paper, research of differentvarieties leaf chlorophyll content, photosynthetic gas exchange parameters, chlorophyll fluorescencecharacteristics and antioxidant enzyme activity parameters and compare them to explore the differentvarieties Upland changes and differences in leaf photosynthesis and antioxidant enzyme responsemechanism in the sunny day under natural conditions. Determine the different varieties Upland cottoncultivar selection of high light efficiency, light inhibition of the differences the photoprotective mechanismsas well as varieties provide a theoretical basis.Method: To ’Huazhong111’,’FB20’,’Jimian158’,’Lukang20’,’NJ01’,’13-1’（2011-2012South fan growingnumber）,’anti-1’,’1-6082’ as test materials, the determination of the content of chlorophyll （Chl）, netphotosynthetic rate （Pn）, stomatal conductance （Gs）, intercellular CO₂concentration （Ci）, transpiration rate（Tr）, stomatal limitation value （Ls） and photosynthetic gas exchange parameters; simultaneousdetermination of the blade initial fluorescence （Fo）, PSII maximum photochemical efficiency （Fv/Fm） theactual photochemical efficiency （ΦPSII）, photochemical quenching （qP） non-photochemical quenching（NPQ） of chlorophyll fluorescence parameters; selected upland cotton leaves determination of the contentof malondialdehyde （MDA）, superoxide dismutase （SOD）, peroxidase （POD）, peroxide and catalase （CAT）and other physiological and biochemical indices.Results: High temperature and high light conditions significantly reduced Pn,Tr and significantly increasedNPQ;’13-1’ and ’1-6082’ varieties Pn, Fv/Fm, ΦPSII, qP level was significantly higher than the remainingsix varieties,’Jimian158’ and ’FB20’ varieties under high temperature and light conditions, Fo increasedsignificantly, Fv/Fm, ΦPSII, qP decreased significantly. Environmental stress, cotton active oxygenmetabolism imbalance MDA content increased, the ’central111’ and ’anti’ varieties by increasing theactivities of antioxidant enzymes to regulate metabolic balance, slowing the adversity caused by theperoxide damage. Different varieties upland cotton leaf antioxidant enzyme activities in photoinhibitionconditions different response.Conclusion: Eight varieties Upland strong high temperature, light and drought in different seasons, theyexhibit different optical protection and antioxidant protection mechanisms under various stress factors.Environmental stress, chlorophyll content in plant cells decline, breaking the synthesis of chlorophyll anddegradation balance significantly affect Pn, Tr, but has little effect on Gs, Ls, Ci, and serious damage to thephotosynthetic apparatus of leaves, inhibition of photosynthetic institutions, the mesophyll cells decreasedphotosynthetic ability.’13-1’and ’1-6082’ varieties in the same adversity can be adjusted more sensitivechlorophyll content and Tr, to reduce the leaves tissue damage and photosynthetic apparatus damage,maintain a high moisture, nutrient absorption and transport of power and CO2the ability to have a stronger the adversity environmental adaptability.’The Hebei cotton158’ and ’FB20’ leaf photosynthetic institutionsseverely damaged, destruction of the PSII photochemical reaction center, the electron transfer process isblocked, more excitation energy consumption in the form of heat dissipation to reduce the degree ofinhibition of light.’Lukang20’ and ’FB20’ varieties in the same adversity can be adjusted more sensitiveNPQ, to reduce damage to the leaf photosynthetic apparatus, reduce Photoinhibition to maintain highphotochemical conversion efficiency and photosynthetic electron transport activity, recovery bladecompared high photosynthetic capacity.’Central111’ and ’anti’ variety has a more agile and efficient activeoxygen scavenging capacity, which can effectively resist adversity.