Effects Of Low Temperature Stress And Temperature Rewarming On The Physiological And Biochemical Indexes Of Sugarcane

In order to study the effects on physiological and biochemical indexes of sugarcane in the low temperature stress and temperature rewarming, variety with good cold hardiness Guitang 28(GT28) and variety of poor cold hardiness Taitang 22 (T22) were chosen as materials in this experiment, methods of natural cultivation and artificial control conditions were used, and indexes were measured respectively as follows:one is that physiological indexes as dialdehyde (MDA) content, peroxidase (POD), soluble sugar content, soluble protein (SP) and so on, were measured in the leaves of varieties of sugarcane on seedlings, perennial seedlings, elongation and process maturity stage, growing in the natural temperature reduction condition, the other is in artificial control experiment, under low temperature stress (5±2℃) and the temperature rewarming to 20℃condition, photosynthetic parameters, chlorophyll fluorescence parameters and other physiological indexes of +1 leaves of sugarcane on seeding stage were determined. The results are as follows:1. In the natural temperature reduction condition, the changes of the content of MDA, Pro, SP and the activity of POD of sugarcane leaf in different growth stages were consistent. The content of MDA and the activity of POD from high to low as follows:seedling, perennial seedlings, elongation, maturity, and that is higher in ROC22 than GT28. MDA content and POD activity are correlated with cold resistance, and POD activity is negatively correlated to MDA content to. The content of Pro was positively correlated with cold tolerance of sugarcane, and the content shows as follows:it is higher in perennial seedlings than seedlings stage, more higher in maturity than elongation stage, and higher in GT28 than that in ROC22.The content of SP performance from high to low as follows:the seedling, elongation, ratoon seedling, and maturity stage, and it is higher in GT28 than that in ROC22.2. In temperature-controlled experiments, before low temperature stress, compared to ROC22, GT28 has high level of the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and low level of intercellular CO2 concentration (Ci). Under low temperature stress, Pn, Gs, Tr decreased, Ci rised; the light curve of ROC22 is unstable, while the GT28 shows from decreasing to a rising with time. Temperature rewarming after 2 days-cold stress, the parameters of the two species are both closer to the CK, the effect is bad on that of treatment rewarming 5,9-days cold stress. But after temperatre rewarming,9 days-low temperature stress treatment is less sensitive in the light that 5-day Stress treatment. Both under low temperature stress and temperature rewarming, the recovery of GT28 is better than ROC22,had its light curve of each parameter are relatively smooth and regular.3. Before cold stress, There is no significant difference in initial fluorescence of two species (Fo); compared to ROC22, GT28 has a higher level of relative electron transport rate (ETR), photochemical rough off coefficient (qP), the effective quantum yield (Y[Ⅱ]) and lower heat dissipation of non-regulatory quantum yield (Y (NPQ)), non-regulatory thermal dissipation quantum yield Y (NO). In low temperature stress, the Fo, ETR, qP and Y[Ⅱ] of two varieties decreased, and the Y (NPQ) and Y (NO) increased. After 2 days cold stress, Y (NPQ) is highest, followed by 5-days stress,9-days stress treatment.5-days cold stress treatment, has highest Y (NO), followed by 9 days,2 days to treatmens. After temperature rewarming, ETR, qP, Y (Ⅱ) increased, but still less than CK; low temperature stress treatment for 2 days has maximum degree of recovery and the recovery of GT28 is greater than that of ROC22. After temperature rewarming, Y (NPQ), Y (NO) of 2-day cold stress treatment reduced; Y (NPQ), Y (NO) of treatment for 5-days cold stress,9-days cold stress of ROC22 increased, Y (NPQ) of GT28 decreased, and Y (NO) of GT28 increased by less than ROC22.4. The content of the three species of photosynthetic pigments under low temperature stress in 2-days low temperature stress dropped to the lowest, as stress time increased, the content of pigment increased gradually, and chlorophyll a remaining lower than that of before stress, chlorophyllb and carotenoids recovered to the level before. After temperature rewarming, the two content of chlorophyll a, chlorophyll b of the two species was lower than before; except 5 days cold stress treatment of GT28, content of carotenoids of the other treatments was no significant change after temperature rewarming.5. In temperature-controlled experiment, changes of the content of MDA, Pro, SP performance the same as in cultivation conditions. They increased first and then decline in the low temperature stress; when temperature increasing, they the decreased, but still higher than the control. Except the content of proline declining fast than GT28, the content other material of ROC22 decline less than GT28; after temperature rewarming, the content of soluble protein of ROC22 has no significant difference with CK, but the GT28 is significantly higher than CK.6. Before cold stress, ROC22 SOD activity is higher than GT28. In low temperature stress, activity of SOD of the two varieties shows increasing first and then decreasing with time increasing, and the declining rate of ROC22 is faster than the GT28; the POD activity of ROC22 decreases and then increases to the CK levels, GT28 is increases first and then decreases to CK level; CAT activity of GT28 performance the same with its SOD, ROC22shows decreasing first and then increasing again showed a declining, that changing instabilitly.With the low temperature stress time increasing, after temperature rewarming, SOD, POD activity increases, and is higher than the control, the increasing rate of GT28 is higher than ROC22; CAT activity of the two species emerged increasing first and then decreasing, but is higher than CK, and is higher in GT28 than ROC22.7. In the temperature controlled experiment, the content of soluble sugar of GT28 increases with stress time increasing, soluble sugar content of ROC22 were mixes. After temperature rewarming, the content of soluble sugar of the two varieties is higher than the control, the longer the cold stress is, and the longer rewarming time is, higher soluble sugar content of the two species is, increase rate of GT28 is greater than ROC22. In summary, short-time of low temperature stress has caused a serious impact on photosynthesis system of ROC22. GT28 has a coordinating oxidase system, high levels of photosynthetic pigments content, discipline change osmotic material and strong adjustment ability to repair itself, making it more resistant to low temperature than ROC22, and more easily adapt to the changes of temperature.