Studies On The Mechanism Of Carbon Metabolism Of Spring Maize And Chemical Regulation Effects Under Different Accumulated Temperature Zones

This study was conducted with different maize varieties of Fengdan3（FD3, coldresistant） and Zhengdan958（ZD958, cold sensitive） to observe the effects ofaccumulated temperature on plant morphological indexes, growth process, dry matteraccumulation, the key enzymes involved in carbohydrate metabolism during grain fillingstage, the grain yield and the effects of PKN chemical regulation of spring maize. Studyon physiological mechanism with temperature characteristics and chemical regulation oncarbohydrate metabolism of two maize varieties, in order to provide theory evidence forhigh-yield cultivation techniques of maize in cold region. This study is of great importantto guarantee the stable high yield of maize in cold region. The results were showed asfollows.1. In the three accumulated temperature zones （for short: ATZ）, the effectiveaccumulated temperature performance, Ⅰ>Ⅱ>Ⅲ ATZ. In2011, the effective accumulatedtemperature of Ⅰ ATZ was82.23and297.91℃higher than that of Ⅱ, Ⅲ ATZ. In2012,the effective accumulated temperature of Ⅰ ATZ was83.93and220.90℃higher than thatof Ⅱ, Ⅲ ATZ. Compared with Ⅱ, Ⅲ ATZ, in Ⅰ ATZ, the sowing date of maize was1-16din advance, which not only prolonged the growth process, especially increasedaccumulated temperature and daily average temperature of spring maize after silking, andthe effective used light and heat resources during the growth stage.2. In Ⅰ, Ⅱ, Ⅲ ATZ, the average temperature in2011was12.43,12.66and13.26℃,respectively, while in2012it was13.22,12.40and13.37℃respectively, from sowing toemergence. The sowing time temperature met the limited temperature for emergence, inthree ATZ, maize at seedling stage was subjected to little low temperature stress. In threeATZ, for FD3, the average temperature in2011was23.07,21.27and18.21℃,respectively, while in2012it was22.62,21.18and18.14℃, respectively during grainfilling period. Maize in the three ATZ at grain filling stage was subjected to serious lowtemperature stress. Especially in Ⅲ ATZ, the frost period was early, resulting in grainfilling deficiency and reduced the yield and quality of spring maize.3. In the three ATZ, the change trend of leaf, leaf sheath, stem and ear dry weight ofFD3and ZD958were the same: it was firstly increase and then decrease, ear dry weight and total dry weight increased with the growth process. PKN treatment increased leaf dryweight and total dry weight in different degree.4. In the three ATZ, the change trend of leaf area index （LAI） and chlorophyllcontent of FD3and ZD958were the same, they all showed single-peak curve changewith the growing process. LAI started to increase gradually from the seedling stage,reached the peak at reproductive growth stage, and then decreased gradually, themaximum chlorophyll content was in the leaves at the early filling stage; Thephotosynthetic rate of FD3and ZD958increased in grain filling stage, and it wasgradually decreased after anthesis. LAI, chlorophyll content and photosynthetic rate wereincreased in different degree by PKN treatment.5. In the three ATZ, there were differences exist for the activity of photosyntheticenzymes （RuBP carboxylase and PEP carboxylase） at different leaf positions of maizevarieties of FD3and ZD958, it showed a single-peak curve or decreased with the grainfilling time. For FD3, the effect of effective accumulated temperature on the leafphotosynthetic enzymes was significantly at early （0²0d） and late （20⁴0d） grainfilling stage. While for ZD958, it was significantly in the whole grain filling stage. Theactivities of RuBPCase and PEPCase were improved in different degree by PKNtreatment, and the leaf photosynthesis was strengthened.6. In the three ATZ, there were differences exist for the activity of sucrosemetabolism enzymes（sucrose synthetase, sucrose-phosphorus synthetase and invertase）and sucrose content at different leaf positions of FD3and ZD958. There was nosignificant correlation between Sucrose content and accumulated temperature of FD3.While for ZD958it was significant positive correlated. For different types of maize, thecorrelations of accumulated temperature and activity of sucrose-metabolizing enzymeswere different. FD3was significantly influenced by temperature in the later grain fillingstage, while for ZD958it was in the whole grain filling stage. Sucrose content andsucrose-metabolism enzymes activity were improved in different degree by PKNtreatment.7. For different type of maize, the correlation of sucrose content andsucrose-metabolizing enzymes activity in leaves was different. For FD3, the correlationof sucrose content and sucrose synthetase（SS） activity in0-10d and20-30d after silkingis greater than that with SPS activity. For ZD958, the correlation of sucrose content andsucrose phosphate synthetase（SPS）activity in whole grain filling stage was greater thanthat with SS activity. of FD3and ZD958with There were significant positive correlationsexist between sucrose content and acid invertase （AI）, neutral invertase （NI） activity forboth maize varieties.8. In the three ATZ, the yield of two maize varieties showed in an order of Ⅰ>Ⅱ>ⅢATZ, the yield ZD958was higher than that of FD3. The yield of two maize varieties was increased in different degree by PKN. In2011, the yield of FD3treatmented by PKN in3ATZ was7.36,552.71and227.51kg·hm^-2, respectively, higher than that of control; whilefor ZD958it was1180.6,1223.97and1261.73kg·hm^-2, respectively. In2012, for FD3itwas118.02,642.79and723.02kg·hm^-2, respectively; while for ZD958it was306.50,311.32and989.53kg·hm^-2, respectively.