玉米增密缩穗的激素机理与化学调控

In maize production, increasing planting density is one of the way for high yield, however, increasing planting density can lead to poor performance: tassel pollens less, pollen viability decreased; the ear shorten, grain number per ear decreased, the decrease of 100 seed weight, finally, the yield potential will be limited. Therefore, the problems on increasing planting density lead to ear smaller are the main obstacles to limit the potential yield of maize. This study will be conducted at Gongzhuling experimental station of CAAS. Take Dongdan 60 (sparse type) and Zhengdan 958 (High density planting) as material, set the density gradient treatment, namely each 45000, 60000, 75000, 90000, 105000 plants per hectare, then ①to determinate the content of endogenous hormones in leaf, stem, root, tassel, ear and grains in each treatment, ②to determinate the differentiation and development process of spike and tassel, ③to determinate the grain grouting dynamic and mature dehydration process, ④to determinate the morphological index of root, stem and leaf, ⑤to determinate the ability of root uptake of water and mineral elements, the photosynthesis, the stalk supporting ability and so on, and then, to analysis the balance of endogenous hormone between vegetative and reproductive organs, to analysis the relationship between the development of reproductive organs and its endogenous hormone content, then, to study the hormone mechanism of increasing planting density led to corn ear shortening. According to the inducing effect of different endogenous hormone on reproductive organ differentiation and grain filling process are not identical, there are certain mutual coordination and balance between endogenous hormone of vegetative organs and reproductive organs, the PGR has a moderating effect on endogenous hormone synthesis, we will developed a new PGR, which is expected to has the following advantages: 1. to induce the differentiation and development of reproductive organs directional, 2. to induce grain filling process smoothly, to induce grain maturation and dehydration , 3. in the high density population condition, the root system absorb more water and inorganic elements, the leaf photosynthesis ability strong, the stalk is not easy to bend and break, root and leaf senescence occurs after the kernel maturity stage. The optimum dosage and the best period of the new regulator will be studied. Then, the new regulator will be sprayed in different treatment in field trials, and the same as above, to determinate the morphological indexes, physiological indexes and endogenous hormone content of vegetative organs and reproductive organs of each treatment, to get the positive effect of this new regulators to ear growth, then getting the chemical regulation mechanism of increasing yield in high density condition. In order to establish chemical control cultivation technology, this study lays the foundation of increasing planting density to get high yield.

增加种植密度导致玉米果穗发育减弱，雄穗花粉量减少，花粉活力降低；雌穗缩小，穗粒数减少，千粒重降低；因此，增密缩穗是限制玉米群体产量潜力的主要因子。本项目以东单60（稀植型）和郑单958（密植型）为试材，采用大田试验与室内测定相结合的方法，设置密度梯度处理，以雌雄穗分化发育、籽粒灌浆和成熟过程中内源激素（组分、含量）动态变化与其形态变化、代谢生理指标变化的相互关系为主线，在形态学、代谢生理与激素生理学水平上，研究玉米增加密度导致果穗缩小的激素机理；从定向调控雌（雄）穗发育、强化籽粒灌浆的角度，研制促进果穗发育的新型植物生长调节剂，并配套适宜的应用技术；在不同密度群体应用新型生长调节剂，在明确化学调控措施对密植群体根茎叶建构与功能、雌雄穗分化发育、籽粒灌浆和成熟过程影响的基础上，揭示其促进玉米高密群体果穗正常发育、扩穗增粒的化学调控机理；为建立密植高产化控栽培技术，实现玉米高产稳产奠定基础。

【项目背景】增加种植密度导致玉米果穗发育减弱，雄穗花粉量减少，花粉活力降低；雌穗缩小，穗粒数减少，千粒重降低；因此，增密缩穗是限制玉米群体产量潜力的主要因子。【研究内容】在大田条件下，以耐密型品种中单909和稀植型品种吉单35为材料，设置不同密度梯度（3000、5000、7000株/亩）处理，①在形态学、代谢和激素生理学水平，明确了高密度群体根茎叶形态建构、雌穗发育、籽粒灌浆、籽粒成熟过程与内源激素的关系；②在形态学、代谢生理与激素生理水平，明确了玉米增加密度导致果穗缩小的激素机理；③从促进冠层光合产物积累，定向调控雌穗发育、强化籽粒灌浆的角度，研制了高光效调节剂，配套应用技术；④在不同密度群体应用新型生长调节剂，在明确调节剂对密植群体根茎叶建构与功能、雌雄穗分化发育、籽粒灌浆和成熟过程影响的基础上，明确了其促进玉米密植群体果穗正常发育、扩穗增粒的化学调控机理。【重要结果】①增加种植密度，导致叶片和籽粒中生长素和赤霉素的含量降低，ABA含量上升，叶片净光合速率下降，群体早衰，雌穗长度缩短，籽粒体积缩小，灌浆速率和籽粒脱水速率下降。乙矮合剂（EC）+聚糠萘合剂(PKN)和EC+赤嘌合剂(GB)双重化控处理，以及高光效调节剂（EC+ALA）处理，均可提高雌穗伸长速度，增加雌穗长度，提高灌浆速率。②增加种植密度，导致穗位叶和籽粒中氮素代谢关键酶NR、GS、GPT和GOT活力降低， SPS、SS、AI、NI活性降低，叶片光合产物合成与供应迟滞，雌穗营养供应受阻，群体早衰，雌穗长度和籽粒干物重积累减少。③EC+PKN和EC+ GB双重化控处理，以及高光效调节剂（EC+ALA）处理，均可提高穗位叶净光合速率，提高叶片和籽粒中NR、GS、GPT和GOT活力，提高SPS、SS、GS、GPT、GOT的活力，促进叶片中氮素的同化和蛋白合成，促进了碳水化合物的合成和运输。