General Botany Laboratory, Institute of Experimental Biology, Faculty of Biology, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 6, 61-614, Poznań, Poland.
Poznań University of Life Sciences, ul. Wojska Polskiego 71a, 60-625, Poznań, Poland.
Photosynth Res. 2022 Oct;154(1):41-55. doi: 10.1007/s11120-022-00953-4. Epub 2022 Sep 3.
Trees regenerating in the understory respond to increased availability of light caused by gap formation by undergoing a range of morphological and physiological adjustments. These adjustments include the production of thick, sun-type leaves containing thicker mesophyll and longer palisade cells than in shade-type leaves. We asked whether in the shade-regenerating tree Acer pseudoplatanus, the increase in leaf thickness and expansion of leaf tissues are possible also in leaves that are already fully formed, a response reported so far only for a handful of species. We acclimated potted seedlings to eight levels (from 1 to 100%) of solar irradiance and, in late summer, transferred a subset of them to full sunlight. Within 30 days, the pre-shaded leaves increased leaf mass per area and became thicker mostly due to the elongation of palisade cells, except for the most shaded individuals which suffered irreversible photo-oxidative damage. This anatomical acclimation was accompanied by a transient decline in photosynthetic efficiency of PSII (F/F), the magnitude of which was related to the degree of pre-shading. The F/F recovered substantially within the re-acclimation period. However, leaves of transferred plants were shed earlier in the fall, indicating that the acclimation was not fully effective. These results show that A. pseudoplatanus is one of the few known species in which mature leaves may re-acclimate anatomically to increased irradiance. This may be an important mechanism enhancing utilization of gaps created during the growing season.
林下更新的树木通过一系列形态和生理上的调整来响应因间隙形成而导致的光可用性增加。这些调整包括产生厚的、太阳型叶片，其含有比阴影型叶片更厚的叶肉和更长的栅栏细胞。我们想知道在阴影再生树种 Acer pseudoplatanus 中，叶片厚度的增加和叶片组织的扩张是否也可能发生在已经完全形成的叶片中，这种反应迄今为止只在少数几个物种中报道过。我们将盆栽幼苗适应 8 个水平（从 1 到 100%）的太阳辐照度，然后在夏末将其中一部分转移到全光照下。在 30 天内，预遮荫的叶片增加了比叶面积和叶片厚度，主要是由于栅栏细胞的伸长，除了最遮荫的个体，它们遭受了不可逆转的光氧化损伤。这种解剖适应伴随着 PSII（F/F）的光合作用效率的短暂下降，其幅度与预遮荫的程度有关。F/F 在再适应期间有了很大的恢复。然而，转移植物的叶片在秋季更早脱落，这表明适应还不完全有效。这些结果表明，A. pseudoplatanus 是少数几种已知的成熟叶片可能对增加的光照进行解剖适应的物种之一。这可能是一种重要的机制，可增强对生长季节中形成的间隙的利用。
