低土壤水分条件下春小麦根系吸水的功能效率研究

The main functions of roots are to absorb water and mineral nutrition from soil to support shoot growth, the cost for the functions is the input of assimilate from shoots. Therefore we can define root function efficiency as the ratio of absorption of soil water / nutrients to input of assimilate from shoots, which represents the trade-off in activity of roots. This research determined the carbon consumption in roots and the function efficiency under the condition of drought stress in spring wheat to explore the yield potential. .Pot experiment shows that under condition of the various soil moisture content root biomass carbon just take up about a quarter of the total carbon consumption in roots including biomass, respiration and exudation; root respiration C is about twice of biomass C, more than the total C of root biomass and exudation. At mature stage, daily biomass C decreased prompt in the old variety (Dingxi 24) treated by drought stress, its daily decrease is more 100 times than total consumption of C in roots, daily respiration C and daily exudation C in roots are 7.89 and 3.75 times of total consumption C in roots, respectively. All these are significantly higher than modern cultivar (Longchun-8139-2) / soil moisture treatments..In another pot experiment, spring wheat plants with small root system in wet and medium soil moisture treatments used less soil water before anthesis, but more water after anthesis than plants treated with lager root system. This lets the soil moisture content in the treatment with small root system is higher than the one with lager root system after anthesis, which is favorable to grain filling and yield formation. In the moderate and severe drought stress treatments, the above ground biomass in the treatment with small root system was lower than that of bigger root system, but the grain yield of former was13% and 34% respectively more than the latter. This means the higher reproductive effort and water use efficiency in the treatment with small root system. .In the experiment of controlling rooting depth, the time when root grown into lower wet soil had great influence on root respiration. The carbon respired by root was significantly increased if the root grown into lower wet soil was occurred at jointing or anthesis stage, however, there had no effect if it occurred at mature stage. Too much root tissue in lower wet soil was not benefit to increasing grain yield and plant positive carbon balance because a large proportion of carbon was respired by root..The stage when roots deepen into wet soil layer is very important for root respiration and grain yield formation. Controlling root deepening into wet soil layer during the period from jointing to anthesis stage can increase significantly root respiration, water use efficiency and grain yield; rooting to wet soil layer before jointing also result in significantly higher root respiration but water use efficiency and grain yield decrease significantly because of too much consumption of assimilate from shoots; if rooting to wet soil layer after anthesis, root respiration has not any response, and water use and grain yield are the lowest. .Root respiration and root biomass decreased significantly when drought occurred during three leaves to tiller period, and grain yield is significantly higher in the modern cultivar Longchun 8139-2 than in the old cultivar Dingxi 24. Root respiration decreases more quickly in Dingxi 24 than in Longchun 8139-2 when drought occurred during jointing to anthesis stage, and grain yield of former was attained the maximum among all the treatments with drought in various stages in Dingxi 24. After re-watering, the root biomass and root respiration rate in Longchun 8139-2 are significantly higher than that of in drought stage, but in Dingxi 24, no matter how is drought or re-watering, the maximum of root dry mass always occurs during the tillering to jointing period. .Root respiration C is higher than root biomass C, and become the most important approach to total C consumption in roots. Crop plants with small

把根系对地上供应水分的能力同消耗同化产物之间的数量关系作为根系水的功能效率。将根系吸水量、干物质生产和产量形成能力统根系对同化产物的消耗联系起来，测定根系分泌物、根呼吸和根生物量作为对能量的消耗，测定根对水的吸收，干物质生产集籽粒产量作为收益，分析小麦根系的产投效率，探讨通过影响根系对同化产物的消耗量，提高产量的潜力。