Studies On Physiological, Morphological Characteristics And Approaches For Super High-yielding Of Super Hybrid Rice

This research take middle-season indica super hybrid rice of new determination as experiment materials, and general yield level of middle-season hybrid rice as control, studied on the yield potential, characteristics of storage capacity, physiological and morphological characteristics in Anhui and Jiangsu province, further exploration of approaches for more higher grain yield, aimed at elucidating the physiological and morphological basis of formation regularity of super high-yielding, revealing the approaches for super high-yielding, discussing the regulating directions for more higher yield, provide theoretical basis for super rice breeding and super-high-yielding cultivation, and the results showed that:1. The gross storage capacity of super hybrid rice is above870kg/667m2,and the actual yield could reach over750kg/667m2.The higher number of population spikelets was a major and direct factor resulting in higher yield, and its corresponding population spikelets is about3500×104/667m2; Combined action of panicle and grain lead to increasing of population spikelets, however, the contribution of this two characters were different in different stage. From middle yield to high yield, panicles and grain numbers contribution were47%and53%, respectively, while, from high yield to super high yield is benefit from larger panicles based on enough panicle number, and the contribution of grain number and panicle number were78.8%and21.1%, respectively. The large panicle was constructed by means of two ways:the first increased the number of primary branches(PB) and its number of grain-setting per PB. The other, the number of secondary branch(SB) was enhanced based on the stable number of grain-setting per SB, in which, the increment of number of SB and total number of grain-setting per plant was a key measure. Super hybrid rice have higher spikelets forming ability, meanwhile, higher glumness is superiority, the centralized reflection is higher single panicle weight; The single panicle weight could be over4.0g,10.9%higher than control; Large panicle and higher single panicle weight are structure peculiarities of storage capacity of super hybrid rice.2. Super hybrid rice have significant superiority of dry matter accumulation, grain yield increased with increase of dry matter accumulation at maturity stage(r=0.886*, r0.05=0.811), while the range of harvest index is about0.5-0.55. Super hybrid rice have higher dry matter accumulation after jointing stage, and the growth rate(CGR) is increasing with the plant growth. After flowering stage, significant higher dry matter accumulated because of higher CGR than control. At the middle and later growth stage, leaf area index(LAI) decreased slowly, which lead to significant higher population leaf area duration(LAD). With the increasing of LAI and LAD, CGR increased significantly, the CGR is302.8g m-2·d-1higher than control in field period.3. Super hybrid rice had high activity of nitrate reductase(NR) and obvious advantages of nitrogen accumulation and utilization, the total amount of nitrogen absorption and accumulation was11.3%more than control. The advantages of nitrogen absorption and utilization of super hybrid rice started from jointing stage and enlarged with growing process, the nitrogen absorption ability of super hybrid rice after heading stage was significantly higher than control, after heading for25d, the rice plant still had certain ability of nitrogen absorption (24g N-667m-2·d-1). Super hybrid rice had the strongest nitrogen absorption efficiency (average at245.3g N·667m-2·d-1) during jointing-booting stage, which was significantly higher than control. The strong ability of nitrogen absorption and utilization after flowering stage increased the N content in functional leaves, slowed down the descending rate of leaf area and prolonged the photosynthetic function duration and high value duration of leaves. In order adapt to the characteristics of nitrogen active metabolism and large absorption amount in later growth stage of super hybrid rice, nitrogen supply should be increased in later stage for super-high-yielding cultivation.4. At booting stage, maximum population leaf area index could reach7.5-8.0, which increased3.4%than control, and the decrease of leaf area after flowering stage slowed down, increased the comparative advantages, at middle grain filling stage and maturity stage, the super hybrid rice had13.8%and16.9%higher LAI than control, respectively. The higher ability of nitrogen absorption is the possible reason of increasing of photosynthetic pigment content (PPC) in function leaf at the later growth stage. During grain filling stage, the content of chla+b is higher than control, and the ratio of chla/b is lower than control at early filling stage, this is a remarkable physiological characteristic of photosynthesis. At the later growth stage, super hybrid rice leaf had higher activities of superoxide dismutase, improved ability of scavenging oxygen free radicals in later stage, which decreased the content of malondialdehyde (MDA) and slowed down leaf presenility, improved the net photosynthetic rate of functional leaves in later stage, and the leaf source capacity increased significantly, so as to significantly improved the ability of photosynthetic production.5. Super hybrid rice had coordinated development of morphological characteristics and physiological characteristics:comparatively ideal plant type, optimized canopy structure, strong and stable supporting system.(1) Super hybrid rice has comparatively ideal plant type:flag leaf has moderate length or little short, longer length of top2nd and3rd leaf, orderly arrangement of function leaves, wide and involution, small basic angle and drooping angle of top three leaves; Dry matter weight of leaves and specific leaf weight is higher significantly, ensure the steady of leaf shape and leaf position; With the plant growth, compared with control, comparative superiority of morphological index is increasing. Good plant type could improve transmittance and decrease extinction coefficient of population. On the basis of above results, ideotype index for more higher grain yield was proposed.(2) Super hybrid rice has optimized canopy structure:the maximum leaf area index could reach330-350cm2per single-stem(10%higher than control), and70%of it is high effective leaf area; Photosynthetic function duration of bottom leaves is26.6%longer than control which caused by improved plant type; Leaf area and dry matter weight are all higher than control, and deceased gently, comparative superiority is increased with plant growth, special leaf weight increased at middle grain filling stage. Shorter basal internode, longer rachis internode, and little higher plant height are the morphological foundation of biological yield, and optimized the leaves structure and position; Higher leaf sheath phimosis degree, and thick wall of leaf sheath are the reasons of stem grow sturdily, and the degree increasing with plant growth; Make sure the index of canopy structure and morphological characteristics for more higher grain yield. (3) Super hybrid rice has strong supporting system:dry matter weight of leaf sheath and stem are higher than control significantly, at grain filling stage, the dry matter which stored in leaf sheath before flowering stage are transformed more than stored in stems, apparent export percentage of leaf sheath and stem are44.9%and14.3%, respectively, and6%and5%decreased than control. However, absolute amount of output from leaf sheath of super hybrid rice is higher than control. Meanwhile, the filling degree of basic internodes is higher than CK significantly, and the degree is increasing with plant growth, especially higher filling degree in leaf sheath is benefit to stabilized leaf area and photosynthetic function, it’s a more important factor for supporting system. The filling and sheath phimosis degree of leaf sheath at the later grain filling stage could as the morphological index for more higher grain yield. Stabilized supporting system enhance the bearing ability and resistance to fracture, and it’s benefit to improve the photosynthetic function at the later growth stage, that’s the most important characteristics of super hybrid rice.6. It compares and analyzes the effect on yield formation and population quality of super hybrid rice in different cultivation patterns, and summarizes the approaches of compensated cultivation for super high yield, and analyzed cultivation principle and yield-increasing mechanism.(1) The suitable beginning population structure confirmed by experiments of seedlings and nitrogen management are follows:sparse planting and proper seedling number and the appropriate N level is17.5kg/667m2; By experiment demonstration and verification, the effects on yield formation and population quality in different cultivation patterns was compared, and bring compensated cultivation for super high yield.(2) It explained cultivation principle of compensated cultivation, revealed yield-increasing mechanism and expounded the core meaning of this approach is to compensate the population leaf area duration, improve the population function after flowering stage.Based on the3rd target yield(900kg/667m2) of super hybrid rice, yield components, physiological and morphological basis, and regulation approaches for getting more higher yield were discussed.