Hembrom Richard, Ünnep Renáta, Sárvári Éva, Nagy Gergely, Solymosi Katalin
Department of Plant Anatomy, Institute of Biology, Faculty of Science, ELTE Eötvös Loránd University, Budapest, Hungary.
Neutron Spectroscopy Department, HUN-REN Centre for Energy Research, Budapest, Hungary.
Physiol Plant. 2025 Jan-Feb;177(1):e14621. doi: 10.1111/ppl.14621.
Investigating the effects of drought stress and subsequent recovery on the structure and function of chloroplasts is essential to understanding how plants adapt to environmental stressors. We investigated Ctenanthe setosa (Roscoe) Eichler, an ornamental plant that can tolerate prolonged drought periods (40 and 49 days of water withdrawal). Conventional biochemical, biophysical, physiological and (ultra)structural methods combined for the first time in a higher plant with in vivo small-angle neutron scattering (SANS) were used to characterize the alterations induced by drought stress and subsequent recovery. Upon drought stress, no significant changes occurred in the chloroplast ultrastructure, chlorophyll content, 77K fluorescence emission spectra and maximal quantum efficiency of PSII (Qy dark), but the actual quantum efficiency of PSII (Qy light) decreased, the amounts of PSI-LHCII complexes and PSII monomers declined, and that of PSII supercomplexes increased. Thickness of the leaf and of the adaxial hypodermis, chloroplast length and granum repeat distance (RD) values decreased upon drought stress, as shown by light microscopy and SANS, respectively. Because of the very slight (nm-range) changes in RD values, the large biological variability (significant differences in RD values among the leaves and studied leaf regions) and the invasive sampling required for this method, transmission electron microscopy (TEM) hardly showed significant differences. On the other side, in situ SANS analyses provided a unique insight in vivo into the fast structural recovery of the granum structure of drought-stressed leaves, which happened already 18 h after re-watering, while functional and biochemical recovery took place on a longer time scale.
研究干旱胁迫及其后续恢复对叶绿体结构和功能的影响，对于理解植物如何适应环境压力至关重要。我们研究了绒叶肖竹芋（Ctenanthe setosa (Roscoe) Eichler），这是一种能够耐受长时间干旱期（断水40天和49天）的观赏植物。首次将传统的生化、生物物理、生理和（超）结构方法与高等植物体内小角中子散射（SANS）相结合，用于表征干旱胁迫及其后续恢复所引起的变化。在干旱胁迫下，叶绿体超微结构、叶绿素含量、77K荧光发射光谱和PSII的最大量子效率（Qy暗）没有显著变化，但PSII的实际量子效率（Qy光）下降，PSI-LHCII复合物和PSII单体的数量减少，而PSII超复合物的数量增加。光学显微镜和SANS分别显示，干旱胁迫下叶片和近轴皮下层的厚度、叶绿体长度和基粒重复距离（RD）值均下降。由于RD值的变化非常微小（纳米级）、生物学变异性大（叶片和所研究叶片区域之间的RD值存在显著差异）以及该方法需要侵入性采样，透射电子显微镜（TEM）几乎没有显示出显著差异。另一方面，原位SANS分析提供了对干旱胁迫叶片基粒结构快速结构恢复的独特体内见解，这种恢复在重新浇水后18小时就已发生，而功能和生化恢复则发生在更长的时间尺度上。
