不同水分胁迫下几种春小麦种子根形态结构的研究

Anatomical Structure of Seminal Root of Spring Wheat under Different Water Stress

实验采用快速冷冻切片法及显微摄像系统观察法对甘肃陇中地区 6个品种春小麦在不同水分状况下的种子根进行了形态结构研究。结果表明 ,在不同程度水分胁迫下的同一品种春小麦 ,种子根后生木质部导管 (中央大导管 )直径有显著的差异 ,但这种变化趋势并不是简单的线性关系。随着水分胁迫的增大 ,不同品种春小麦种子根中央大导管的直径有不同的变化趋势。不同品种春小麦在不同程度的水分胁迫下 ,随着胁迫的增大 ,各品种中央大导管直径的变化都逐渐趋于同一区域 。

In semi arid area, root under drought stress should absorb as much water as it can for its needs. The fights for water among individals come along. In ordinary view, the developed root system is favorable for plant absorbing water. But crop production is a process of population. Its objective is to raise drought resistance of population, thus to acquire stable and high yield under drought conditions. In the semi arid area, the connection between the behavior of roots and the yield of a water limited crop can be expressed as follows: yield=water used×water use efficiency×harvest index. Considering the water acquired during all growing period being limited, drought resistance breeding must focus on the rise of water use efficiency and harvest index. Crop yield in drought condition may largely depend on the amount of usable water contained in the soil at about the time of flowering. Passioura (1972,1976) pointed out that when the wheat is growing on a limited supply of stored soil water, small roots can increase the resistance to water flowing and therefore they would conserve some of water for the critical period during flowering and grain filling. Spring wheat typically relies on a very few seminal axes and attendant laterals to collect water in the subsoil, so the activity of seminal root and diameter of the main xylem vessel directly affect the ability of water absorption. Small diameter of the xylem in the upper part of the seminal root like a “bottleneck” is resistant to the flowing of water, which restricts the absorption and transpiration of water and decreases the water use in the former growing period, and therefore it saves some water for later. Through the cryostat microtome method,the anatomical structure of the seminal root of six spring wheat varieties had been investigated. Under different water conditions, the diameter of the main xylem vessel in the seminal axes of the same variety have great differences,and show different change trends with the development of water stress,but concentrate on the same area at the end. This area may be the best diameter of the main xylem vessel to adapt to water deficit. The diameter of seminal root was not in a simple line relation with the diameter of main xylem vessel. The thick cortex has the function of water reserve.