Schoettle Anna W., Smith William K.
USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Ft. Collins, CO 80526, USA.
Tree Physiol. 1991 Jul-Sep;9(1_2):245-254. doi: 10.1093/treephys/9.1-2.245.
In Pinus contorta Doug. ssp. latifolia (Engelm.), annual shoot length increment, annual foliage production per shoot, and the daily integral of photosynthetically active radiation (DPAR) at shoot tips increased with height in the crown, whereas leaf longevity decreased. There was a decrease in DPAR along the shoot from the tip to beyond the oldest leaves, and the value reached at the point just proximal to the oldest leaf cohort was the same for all shoots from all crown locations, regardless of the age of the oldest leaves. The results suggest that shoot elongation, leaf production and leaf retention are controlled by the light environment within the crown. Because high irradiance promotes leaf production and low irradiance promotes leaf shedding, foliage is not randomly distributed in the crown.
在扭叶松（Pinus contorta Doug. ssp. latifolia (Engelm.)）中，一年生新梢长度的增加量、每枝新梢的年叶产量以及新梢顶端的光合有效辐射日积分（DPAR）随树冠高度的增加而增加，而叶片寿命则下降。从新梢顶端到最老叶片以外，沿新梢的DPAR下降，并且对于来自所有树冠位置的所有新梢，在最老叶簇近端的那一点所达到的值是相同的，无论最老叶片的年龄如何。结果表明，新梢伸长、叶片产生和叶片保留受树冠内光照环境的控制。由于高辐照度促进叶片产生，低辐照度促进叶片脱落，所以叶片在树冠中并非随机分布。
