Studies On Leaf Redundancy In High Yield Maize (Zea May L.) And Regulation

In order to determine whether or not there is the phenomenon of leaf redundancy in high-yielding maize colony and the effect of leaf-cut to the physiology character, we choose four high-yielding maize hybrids :JH5,DH3719,CS1,CS3,and study at the low plant-density of 15000 plant/ha (2007) , and screen out the redundant type and non-redundant type through compare the result of the yield due to leaf-cutting under the conditions of low-density. Then according to the hybrid's character at the high plant-density(2008) to make further study. We researched the effect of different leaf-cutting on yield and physiological mechanisms at high plant-density. The principal results were as follows:1 Grain yield and characters of matter accumulationUnder the low plant-density of 15,000/ha, four varieties of maize was made of the whole leaf-cutting treatment, the production is decreased. But the results of the comparison of yield differences is different significantly. The yield difference of CS1 and DH3719 leaf-cutting 1/4 with CK is not significant. But after leaf-cutting 1/2, the changes of yield differences are very significant, which explains that the leaves of two varieties under the conditions of the low-density existed a certain degree redundancy. The yield differences about JH5 and CS3 on the three treatments were significant, which explained that the yield was sensitive to reducing leaf area, and didn't exist leaf redundancy under the low-density. According to the comparation of the yield decline after leaf-cutting in 2007, and the author selected the varieties of CS1, CS3 in 2008, which is the redundancy type and non-redundant type under the conditions of low-density.Under the high-density, the biomass above-ground of two varieties of leaf-cutting 1/4 are slightly higher than the CK and the leaf-cutting 1/2, which are reflected in leaf-cutting 1/4 > CK> leaf-cutting 1/2. And with the leaf-cutting 1/4, dry matter is respectively raised to 2.5% and 7.6% compared to CK, but the differences are not significant. After two varieties leaf-cut 1/4, grain yield was slightly increased by 2.3% and 1.5% respectively. The differences were not significant. The results of this study show that: under high-density, the different redundancy types in the low-density exist leaf redundancy phenomena. Removing redundant groups can coordinate the relationship between source and sink and can improve the population quality, and improve the dry matter accumulation and grain yield.The study showed that: the Richards model can be used to simulate grain-filling process, and the decision coefficient (R) reached 0.997 ~ 0.998. The active filling time of CS1 different treatments is more than 50 days. The active filling time of CS1 with leaf-cutting 1/4 is the longest, which is more than 53 days. The active filling time of non-redundant different treatments of CS3 is between the 48d-50d, leaf-cutting 1/4 is the longest too.2 The photosynthetic traits after disposing of Leaf redundancy Two types of the maize varieties in the high density with leaf-cutting 1/4 treatment can improve the canopy extinction coefficient, and the differences are significant (P<0.05). There is no significant changes about CS1 leaf-cutting 1/2 and CK, and there is significant changes about CS3 leaf-cutting 1/2 and CK.Chlorophyll content of two different redundancy tapes of maize varieties under low-density conditions were higher than CK after cutting leaf in high-density. In the later growing stage, the decline of chlorophyll content is lower than the CK. Chlorophyll a/b values with leaf-cutting is higher than CK overall, and shows the trend of the greater degree of leaf-cutting the greater chlorophyll a/b value. Especially after anthesis 30 days, it is increased in chlorophyll a/b of the leaf-cutting treatment of two varieties values with the CK significantly. The carotenoid content after leaf-cutting (after anthesis) is lower than the CK, after anthesis 50 days, there remained at a high carotenoid content.After growing stage of leaf-cutting, the net photosynthetic rate (Pn) of ear leaf with leaf-cutting were higher than CK, and showed that the high- photosynthesis duration is longer than CK. The somatal conductance (Gs) of ear leaf were higher than those of CK. The intercellular CO2 concentration (Ci) of CK was significantly lower than leaf-cutting treatments.ΦPSII and Fv/Fm of two different redundancy tapes of maize varieties under low-density conditions were higher than CK after cutting leaf in high-density. The efficiency actual photochemical efficiency of PSII (ΦPSII) was declining after leaf-cutting 10 days. The changes of maximal photochemical of PSII (Fv/Fm) on anthesis 30 days was stable, but it showed quite different after 30days. Compared between the two varieties, there is no significant difference.3 The membrane permeability and protective enzyme activity after disposing of Leaf redundancyThe soluble protein content, SOD activity, POD activity, CAT activity of two different redundancy tapes of maize varieties under low-density conditions were higher than CK after cutting leaf in high-density, which could improve plant resistance after the leaf-cutting, delay leaf aging and improve scavenging ability of reactive oxygen on maize leaves. The malondialdehyde (MDA) content of CK was higher than the leaf-cutting treatments overall, which could slow down membranaceous peroxide level of leaf cells after leaf-cutting, and delayed leaf senescence.4. The characters of N, P, K accumulation after disposing of Leaf redundancy The nitrogen content of the leaves and grains of two different redundancy tapes of maize varieties under low-density conditions were higher than CK after cutting leaf in high-density, the phosphorus content is the same as it. The leaf-cutting 1/4 and 1/2 boosted plant to absorb N, P under high-density which ensured that the leaves have higher photosynthetic activity and keep green in the late growing stage. It may be one reason of biomass and grain yield without significant reduction under high-density with the leaf-cutting 1/4 and 1/2. The changes of K content among different treatments of stem and leaf sheath are large. There is no significant changes in the grain compared with CK.Under the conditions of high yield, leaf-cutting 1/4 treatment can improve the grain N content and plant total nitrogen content at harvest stage, and leaf-cutting can increase nitrogen harvest index, and shows the trend of the greater degree of leaf-cutting the greater nitrogen harvest index .