| Wheat-maize double cropping is the main cropping system of grain production on Hebei Plain. The two main double cropping models, summer maize sowed inter-rows of winter wheat before wheat harvest, or directly sowed after wheat harvest, have long been eliminating and replacing each other. The crop yield components of wheat/maize compound community have been widely studied, but the effects of wheat/maize compound communities formed through different cropping models on the eco-physiological characteristics of crop photosynthetic organs were rarely reported. In this paper, different wheat/maize compound communities were created, the eco-physiological characteristics of photosynthetic organs in the compound communities and the dynamics of community yield characters were studied during 2007-2010, aiming at providing experimental support for highly yielding cultivation of winter wheat and summer maize in Hebei Province. The main results were as follows.1 On the basis of same planting densities (seedlings per m2), the community and individual characters of wheat were different between the two spacing form treatments,"equal row spacing"(all 15 cm apart) and"three narrow with one wide"(16.7+16.7+26.7 cm apart). The diameters of basal internodes of the stem, the amounts of total spikelets, grains and grain weight per spike all positively correlated to the width of average row space significantly, wider row space was beneficial to the superiority of individual characters of wheat. However, the community characters, such as maximum leaf area index (LAI), the amounts of culms (the sum of main stems and tillers) and spikes were all higher in the 15 cm equal row spacing treatment, although the difference of grain yield was not significant between the two spacing forms, owing to the interaction of the three yield components. Although the maize was inter-planted before wheat harvest and directly sowed after wheat harvest with the same density, 7.5 plants per m2, the ears of earliest inter-planting treatment had least ears per m2 in the two years, 2008 and 2009, and the grain yield of directly sowing maize (sowed on June 16) were higher than those of all the inter-planting treatments (sowed on June 1, 6 and 11) in 2008, and higher than most of the inter-planting treatments in 2009. The yearly grain yields (wheat + maize) was also higher for the treatment 15 cm equal row spacing wheat followed by directly sowing maize in the two years. All the field operations of the treatment can be done mechanically, and was, therefore, the most feasible wheat-maize double cropping model. The yearly grain yields of the relay compound community, maize inter-planted 5~7 days before harvest of wheat which was planted in"three narrow with one wide", was also higher in the two years. Earlier inter-planting maize could escape the peak time of irrigation after directly sowing maize, and was, therefore, a measure of activating the field operations.2 Under different compound community groups, the impact of wheat on the photosynthetic performance a certain reflected in the different spacing forms. Spacing form of"three narrow with one wide"(16.7cm +16.7cm +26.7cm), with marginal effect and the populations maintain a certain transmission rate have more advantages compared to the spacing form of"equal row spacing"(all 15 cm apart) on photosynthesis. The spacing form of"three narrow with one wide"(16.7cm+16.7cm+26.7cm) with marginal effect, the high value of soluble protein content and chlorophyll content in leaf which maintain longer, the function of the middle and lower leaves also maintain longer. As competition of wheat, the inter-planting of maize caused a negative impact on seedling growth before June 6. Soluble protein content, photosyntheticrate, Rubp carboxylase activity, PEP carboxylase activity, and chlorophyll content respectively decreased by 30.0%, 27.0%, 48.1%, 59.5%,18.5% under different sowing dates of inter-plated maize in wheat fields or direct seeding.3 The mesophyll cells of winter wheat and summer maize may all be divided into two types: one was termed regular linked cell, and another was termed irregular lobed cell. Leaves anatomical structure of winter wheat was mainly reflected in the different spacing forms. The leaf blades spacing form of"three narrow with one wide"(16.7cm+16.7cm+26.7cm) were thicker than that of the spacing form of"equal row spacing"(all 15 cm apart). Leaf thickness decreased with leaf position increasing on the stems between two kinds of spacing form. Compared two kinds of spacing form, the percentage of more linked mesophyll cells of leaves of wheat under spacing of"three narrow with one wide"(16.7cm +16.7cm +26.7cm) increased quickly than that of spacing of"equal row spacing"(all 15 cm apart). The size of mesophyll cells decreased was on the coutary. Leaf thickness of maize was the greatest impact of previous crops of wheat during seedling stage.4 This study indicated that the chlorophyll content, the holding-green time and the net photosynthetic rate of plant leaves with border row treatment were all higher than that of other spacing form treatments. As for yield traits, spacing of"equal row spacing"(all 15 cm apart),"three narrow with one wide"(15 cm+15 cm+ 25 cm) and"four narrow with one wide"(14 cm+14 cm +14 cm+25 cm) showed superiority and higher than other spacing forms. There was positive correlation between average increasing of the line width and yield on different levels. The average spacing form of wheat ranged from 15cm to 20cm in which population and yield can be improved optimum in different row spacing. However,"equal row spacing"(all 15 cm apart) treatment without significant differences in yields with"three narrow with one wide"(15 cm+15 cm+ 25 cm) and"four narrow with one wide"(14 cm+14 cm +14 cm+25 cm) treatments, along with the way of maize direct seeding after wheat, was advantaged in increasing all-year yield and mechanized operation, and should be the development target of Hebei plain in future. In this research, wider row spacing had been kept in the treatments of"three narrow with one wide"(15 cm+15 cm+ 25 cm) and"four narrow with one wide"(14 cm+14 cm +14 cm+25 cm), of which the Light transmittances been convenient for maize relay cropping production in the latter growth stage of wheat were higher and offered more light energy for the growth of maize seeding in wheat ridge than that of"five narrow with one wide"(11 cm+11 cm +11 cm +11 cm +22 cm)and"six narrow with one wide"(10 cm + 10 cm +10 cm +10 cm + 10 cm + 20 cm) treatments.5 Compared of different spacing forms such as"equal row spacing"(15cm),"three narrow with one wide"(15 cm+15 cm+25 cm),"four narrow with one wide"(14 cm+14 cm +14 cm+25 cm),"five narrow with one wide"(11 cm+11 cm+ 11 cm+11 cm+ 22 cm),"six narrow with one wide"(10 cm+ 10 cm+ 10 cm+ 10 cm+ 10 cm+ 20 cm), either eco-physiological characteristics of photosynthetic apparatus or yield traits were optimum under spacing of"equal row spacing"(15cm),"three narrow with one wide"(15 cm+15 cm+25 cm),"four narrow with one wide"(14 cm+14 cm +14 cm+25 cm). The study also showed that strong gluten wheat and middle gluten wheat yield was not due to the different types of gluten. The varieties with lower yield such as middle gluten Shi 4185, and strong gluten wheat Gao 8901 were bred relatively early. The maximum Chlorophyll content of the two varieties was lower than other ones , duration was short,the mean photosynthetic rate was lower too. Compared to Shi 4185, Gao 8901 polycyclic mesophyll cells of each leaf were in smaller proportion, the cells were larger, but the yields of these two varieties are not significantly different. Considering the biological production and economic factor of the two varieties, we found that the biological production of Gao 8901 was high, but the economic factor was low. |
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