农林间作模式下扁桃树冠截光对冬小麦籽粒产量形成的影响机制研究

Agro-forestry intercropping is the main mold of agriculture production in southern area of Xinjiang, with the tree age and crown volume increased, shading stresses caused by tree canopy light interception become the main reasons for the dramatic reduction of intercropping crop outputs. The results of our previous studies shown that optimization renovation of almond (full fruit period) tree from could effectively improve the crops production which in the intercropping systems. But the wheat grain yield reduce influence mechanism caused by tree canopy light competition is not clear, restricts the healthy development of intercropping systems. We use almond-winter wheat intercropping system as the research objects, by setting different almond tree-from treatments, through field observation and physical chemical indicators, enzymology, molecular biological laboratory detection to analysis the correlations between intercropping area light environment, wheat photosynthetic physiology, grain filling character, endogenous hormone contents , key enzyme activity and related gene expression, grain yield components and the shading intensity caused by tree. Reveal the critical periods and key factors which influence the grain yield by shading; exploring the regulatory relationships between endogenous hormone, key enzymes activity, gene expression and grain production. Considering the change of light intensity and the spectral composition, elucidate the mechanism of tree canopy shading affect winter wheat grain yield formation. So as to provide theoretical basis for optimization renovation of tree from and increase grain yield of intercropping winter wheat.

果粮间作是南疆主要的农业种植模式，随着树龄和树冠体积的增大，果树遮阴胁迫成为造成间作物减产的主要原因。项目组前期研究发现对盛果期扁桃树形进行优化改造，能有效提高冬小麦的产量。但果树冠层截光对小麦籽粒产量形成的影响机制还不清楚，限制了这一间作体系的健康发展。本项目以扁桃-冬小麦间作模式为研究对象，设置不同树形处理和对照，采用田间观测与室内理化指标、酶学、分子生物学检测相结合的研究方法，分析树冠截光引起的小麦冠层光环境改变，及光环境改变对小麦光合生理、灌浆特征、内源激素含量、关键酶活性、相关基因表达及籽粒产量构成的影响及其相关关系；探讨影响冬小麦籽粒产量形成的关键时期和关键因子；揭示内源激素含量、关键酶活性及基因表达对小麦籽粒产量形成的调控关系，从而阐明果树树冠截光对冬小麦籽粒产量形成的影响机制，为南疆间作模式下果树树形结构优化、小麦优质高产提供实践基础和理论依据。

果粮间作是新疆南疆地区的主要农业生产模式，南疆三地州果麦间作面积超过333000hm²。树冠截光成为间作冬小麦大幅减产的主要原因，严重制约了果粮间作模式可持续发展。因此，明确树冠截光对小麦籽粒产量影响及其生理机制，对于优化果粮间作模式具有重要意义。本项目以扁桃-冬小麦间作模式为研究对象，设置不同树形处理，采用田间观测与室内理化指标、酶学、分子生物学检测相结合的研究方法，分析树冠截光对小麦产量、品质的影响程度及内在机制。研究结果表明：1．树冠截光对间作区域光照强度、光照时长和光质组成均有较大影响，冬小麦拔节期至抽穗期约15d时间为快速消减期，抽穗期后遮阴达到最大水平。树冠截光对PAR的影响范围为树高的1.50倍，冠高的1.70倍和冠幅1.38倍。 “红橙/蓝紫”、“近红光/远红光”和“红橙/远红外”3个光质参数可作为光质的评价参数。间作小麦产量和树冠截光程度密切相关，重度截光产量显著降低，轻度截光产量轻微降低、千粒重显著提高。影响各产量构成指标的关键时期和关键因子分别为，千粒重：灌浆期光照强度，单位面积有效穗数：拔节期PAR日均值、孕穗期 “红光/远红光”，穗粒数：孕穗期至花期PAR强度。间作导致花期和灌浆期旗叶光合能力降低，叶绿素、可溶性蛋白含量下降，最大净光合速率、光系统Ⅱ的实际光合效率降低，对花后光合产物的积累影响较大。轻度遮阴情况下群体光合速率有显著的补偿现象。间作通过光强和光质的改变影响籽粒中激素含量、淀粉酶相关基因表达、淀粉合成关键酶活性进而对籽粒灌浆过程和籽粒干物质积累造成影响。间作模式下，小麦直链/支链降低，蛋白质组份改变，氨基酸含量、氨基酸评分升高，营养品质改变。小冠半圆形对冬小麦产量品质影响小，适于间作。充分利用花期之前较好的光照条件，提高花前光合产物积累量；避免贪青晚熟，促进植株积累碳同化物向籽粒运转，提高收获指数是间作模式下通过农艺措施提高籽粒产量的2条有效途径。