Collier D E, Thibodeau B A
Department of Botany, Erindale College, University of Toronto, Mississauga, Ontario L5L 1C6, Canada.
Tree Physiol. 1995 Nov;15(11):759-64. doi: 10.1093/treephys/15.11.759.
Changes in respiration rate, chemical content and chemical concentration were measured in leaves of field-grown Populus tremuloides Michx. and Quercus rubra L. trees throughout the growing season and autumnal senescence. Chlorophyll, soluble sugar, N, P, K and Mg contents and concentrations all declined during leaf senescence, whereas Ca content and concentration increased. Leaf dry mass per area declined 24 and 35% in P. tremuloides and Q. rubra, respectively, during senescence. In leaves of both species, respiration rates peaked during leaf expansion in the spring and then declined, as a result of reduced cytochrome-mediated respiration, to reach relatively constant rates by midsummer. In senescing P. tremuloides leaves, respiration rates remained relatively constant until mid-October and then declined rapidly. In senescing Q. rubra leaves, respiration rates increased in late September, as a result of the appearance of residual respiration that could not be reduced by respiratory inhibitors, and then declined quickly in early November. No changes in alternative pathway respiratory activity were observed in leaves of either species during senescence until late autumn when rates declined. Because respiration rates were correlated with both leaf sugar and nitrogen content during leaf senescence, we conclude that respiration rates were maintained or increased during leaf senescence to supply energy for degradation and mobilization of chemical constituents.
在整个生长季节和秋季衰老过程中，对田间生长的颤杨（Populus tremuloides Michx.）和红栎（Quercus rubra L.）树叶的呼吸速率、化学成分和化学浓度变化进行了测量。在叶片衰老过程中，叶绿素、可溶性糖、氮、磷、钾和镁的含量及浓度均下降，而钙的含量和浓度增加。在衰老过程中，颤杨和红栎单位面积的叶片干质量分别下降了24%和35%。在这两个物种的叶片中，呼吸速率在春季叶片扩展期间达到峰值，然后由于细胞色素介导的呼吸作用减弱而下降，到仲夏时达到相对稳定的速率。在衰老的颤杨叶片中，呼吸速率在10月中旬之前保持相对稳定，然后迅速下降。在衰老的红栎叶片中，由于出现了呼吸抑制剂无法降低的残余呼吸作用，呼吸速率在9月下旬有所增加，然后在11月初迅速下降。在衰老过程中，直到深秋呼吸速率下降之前，未观察到这两个物种的叶片中交替途径呼吸活性有任何变化。由于在叶片衰老过程中呼吸速率与叶片糖和氮含量相关，我们得出结论，在叶片衰老过程中呼吸速率得以维持或增加，以便为化学成分的降解和转运提供能量。
