Calzavara A K, Rocha J S, Lourenço G, Sanada K, Medri C, Bianchini E, Pimenta J A, Stolf-Moreira R, Oliveira H C
Department of Animal and Plant Biology, UEL - State University of Londrina, Londrina, Brazil.
Plant Biol (Stuttg). 2017 Sep;19(5):720-727. doi: 10.1111/plb.12592. Epub 2017 Jul 15.
The re-composition of deforested environments requires the prior acclimation of seedlings to full sun in nurseries. Seedlings can overcome excess light either through the acclimation of pre-existing fully expanded leaves or through the development of new leaves that are acclimated to the new light environment. Here, we compared the acclimation capacity of mature (MatL, fully expanded at the time of transfer) and newly expanded (NewL, expanded after the light shift) leaves of Guazuma ulmifolia Lam. (Malvaceae) seedlings to high light. The seedlings were initially grown under shade and then transferred to full sunlight. MatL and NewL were used for chlorophyll fluorescence and gas exchange analyses, pigment extraction and morpho-anatomical measurements. After the transfer of seedlings to full sun, the MatL persisted and acclimated to some extent to the new light condition, since they underwent alterations in some morpho-physiological traits and maintained a functional electron transport chain and positive net photosynthesis rate. However, long-term exposure to high light led to chronic photoinhibition in MatL, which could be related to the limited plasticity of leaf morpho-anatomical attributes. However, the NewL showed a high capacity to use the absorbed energy in photochemistry and dissipate excess energy harmlessly, attributes that were favoured by the high structural plasticity exhibited by these leaves. Both the maintenance of mature, photosynthetically active leaves and the production of new leaves with a high capacity to cope with excess energy were important for acclimation of G. ulmifolia seedlings.
对森林砍伐后的环境进行重新植被恢复需要在苗圃中让幼苗预先适应全日照环境。幼苗可以通过使已有的完全展开的叶片适应，或者通过发育适应新光照环境的新叶来克服过多的光照。在此，我们比较了危地马拉破布木（锦葵科）幼苗的成熟叶（MatL，转移时已完全展开）和新展开叶（NewL，光照改变后展开）对强光的适应能力。幼苗最初在遮荫条件下生长，然后转移到全日照环境中。MatL和NewL用于叶绿素荧光和气体交换分析、色素提取以及形态解剖测量。将幼苗转移到全日照环境后，MatL持续存在并在一定程度上适应了新的光照条件，因为它们在一些形态生理特征上发生了变化，维持了功能性电子传递链和正的净光合速率。然而，长期暴露在强光下导致MatL发生慢性光抑制，这可能与叶片形态解剖特征的可塑性有限有关。然而，NewL表现出较高的能力，能够将吸收的能量用于光化学反应并无害地耗散多余能量，这些特性得益于这些叶片所表现出的高结构可塑性。对于危地马拉破布木幼苗的适应而言，维持成熟的、具有光合活性的叶片以及产生具有高能力应对多余能量的新叶都很重要。
