Effect of assimilate utilization on photosynthetic rate in wheat
Effect of assimilate utilization on photosynthetic rate in wheat
复制标题
同化物利用对小麦光合速率的影响
作者：
R. King;I. Wardlaw;L. T. Evans
开花后两周，小麦籽粒迅速灌浆，旗叶的光合速率。在所用条件下，Gabo在20和30 mg CO2 dm-2叶表小时-1之间。约45%的旗叶同化物转运到穗部，只有12%左右转运到根和新梢，去穗后3-15小时内旗叶净光合速率下降约50%，旗叶~（14）C标记同化物的流出量明显减少，随后无穗植株的其它叶片全部变暗，导致旗叶恢复。通过气体分析和14 CO2固定测定的叶片光合作用，以及增加同化物向根和幼枝的转运。暗呼吸速率的微小变化伴随着光合速率的这些主要的、可逆的变化。在连续的高强度光照下一个多星期后，完整植株旗叶的光合速率显著下降，但在黑暗中一段时间后可以恢复，或者通过喷洒DCMU抑制穗的光合作用。穗部光合作用的抑制增加了标记同化物从旗叶向穗部的转运，而不影响叶片糖水平。穗下秆施用TIBA抑制了生长素向秆部的移动，但对旗叶光合作用没有影响。这些结果表明，至少在这个系统中，旗叶的光合作用直接由对旗叶同化物的需求来调节，而不是间接地通过由“库”器官产生的生长素在叶中的作用来调节。
Two weeks after anthesis, when the grain is filling rapidly, the rate of photosynthesis by flag leaves of wheat cv. Gabo was between 20 and 30 mg CO2dm-2leaf surface hour-1under the conditions used. About 45% of flag-leaf assimilates were translocated to the ear, and only about 12% to the roots and young shoots.On removing the ear, net photosynthesis by the flag leaves was reduced by about 50% within 3–15 hours, and there was a marked reduction in the outflow of14C-labelled assimilates from the flag leaves.Subsequent darkening of all other leaves on plants without ears led to recovery of flag-leaf photosynthesis, as measured by gas analysis and14CO2fixation, and to increased translocation of assimilates to the roots and young shoots. Minor changes in the rates of dark respiration accompanied these major, reversible changes in photosynthetic rate.After more than a week in continuous, high-intensity light, the rate of photosynthesis by flag leaves of intact plants had fallen considerably, but could be restored again by a period in darkness, or by inhibiting photosynthesis in the ears by spraying them with DCMU. The inhibition of ear photosynthesis increased translocation of labelled assimilates from the flag leaf to the ears, without affecting leaf sugar levels.The application of TIBA to the culm below the ear inhibited auxin movement throught the culm, but had no influence on flag-leaf photosynthesis.These results suggest that, at least in this system, photosynthesis by the flag leaf is regulated directly by the demand for assimilates from the flag leaf and not indirectly through action in the leaf of auxins produced by the “sink” organs.