Jurczyk Barbara, Grzesiak Maciej, Pociecha Ewa, Wlazło Magdalena, Rapacz Marcin
Department of Plant Physiology, Faculty of Agriculture and Economics, University of Agriculture in Kraków, Kraków, Poland.
Institute of Plant Physiology, Polish Academy of Sciences, Kraków, Poland.
Front Plant Sci. 2019 Jan 9;9:1963. doi: 10.3389/fpls.2018.01963. eCollection 2018.
Photosynthetic acclimation to cold conditions is an important factor influencing freezing tolerance of plants. Photosynthetic enzyme activities increase as part of a photochemical mechanism underlying photosynthetic acclimation to low temperatures. Additionally, a non-photochemical mechanism may be activated to minimize photooxidative damage. The aim of this study was to test the hypothesis that differences in stomatal conductance in plants with contrasting freezing tolerances induce various strategies for photosynthetic acclimation to cold stress. Different stomatal behaviors during the prehardening step resulted in diverse plant reactions to low-temperature stress. Plants with a relatively low freezing tolerance exhibited decreased stomatal conductance, resulting in decreased photochemical activity, faster induction of the non-photochemical mechanism, and downregulated expression of two Rubisco activase (A) splicing variants. In contrast, plants with a relatively high freezing tolerance that underwent a prehardening step maintained the stomatal conductance at control level and exhibited delayed photochemical activity and A expression decrease, and increased Rubisco activity, which increased net photosynthetic rate. Thus, in barley, the induction of photoinhibition avoidance (i.e., non-photochemical photoacclimation mechanism) is insufficient for an effective cold acclimation. An increase in cold-induced net photosynthetic rate due to open stomata is also necessary.
光合作用对寒冷条件的适应是影响植物抗冻性的一个重要因素。作为光合作用适应低温的光化学机制的一部分，光合酶活性会增加。此外，可能会激活一种非光化学机制，以尽量减少光氧化损伤。本研究的目的是检验以下假设：具有不同抗冻性的植物气孔导度差异会引发光合作用适应冷胁迫的各种策略。预硬化阶段不同的气孔行为导致植物对低温胁迫产生不同反应。抗冻性相对较低的植物气孔导度降低，导致光化学活性降低、非光化学机制诱导加快以及两种核酮糖-1,5-二磷酸羧化酶/加氧酶激活酶（A）剪接变体的表达下调。相比之下，经过预硬化阶段的抗冻性相对较高的植物将气孔导度维持在对照水平，光化学活性延迟降低，A表达下降，核酮糖-1,5-二磷酸羧化酶活性增加，净光合速率提高。因此，在大麦中，避免光抑制（即非光化学光适应机制）的诱导不足以实现有效的低温驯化。通过开放气孔导致冷诱导净光合速率增加也是必要的。
