Peršić Vesna, Melnjak Anja, Domjan Lucija, Zellnig Günther, Antunović Dunić Jasenka
Department of Biology, Josip Juraj Strossmayer University of Osijek, 31000 Osijek, Croatia.
Institute of Biology, University of Graz, 8010 Graz, Austria.
Plants (Basel). 2025 Jun 20;14(13):1907. doi: 10.3390/plants14131907.
is a suitable model organism for investigating plant developmental influences due to its intracolonial variations in response to various environmental fluctuations, like nutrient deficiency. In this study, transmission electron microscopy was used to examine age-dependent variation in chloroplast ultrastructure, while pigment levels (chlorophyll and anthocyanins), starch accumulation, and metabolic activity (photosynthetic and respiratory rates) were measured to determine metabolic responses to sulfur deficiency. For a comprehensive insight into electron transport efficiency and the redox states of the photosynthetic apparatus, rapid light curves, chlorophyll fluorescence (JIP test parameters), and modulated reflection at 820 nm were analyzed. Under S deficit, mother fronds relied on stored reserves to maintain functional PSII but accumulated reduced PQ pools, slowing electron flow beyond PSII. The first-generation daughter fronds, despite having higher baseline photosynthetic capacity, exhibited the largest decline in photosynthetic indicators (e.g., rETR fell about 50%), limitations in the water-splitting complex, and reduced PSI end-acceptor capacity that resulted in donor- and acceptor-side bottlenecks of electron transport. The youngest granddaughter fronds avoided these bottlenecks by absorbing less light per PSII, channeling electrons through the alternative pathway to balance PQ pools and redox-stable PSI while diverting more carbon into starch and anthocyanin production up to 5-fold for both. These coordinated and age-specific adjustments that provide response flexibility may help maintain photosynthetic function of the colony and facilitate rapid recovery when sulfur becomes available again.
由于其在菌落内部对各种环境波动（如养分缺乏）的反应存在差异，是研究植物发育影响的合适模式生物。在本研究中，使用透射电子显微镜检查叶绿体超微结构的年龄依赖性变化，同时测量色素水平（叶绿素和花青素）、淀粉积累和代谢活性（光合和呼吸速率），以确定对硫缺乏的代谢反应。为了全面了解电子传递效率和光合装置的氧化还原状态，分析了快速光曲线、叶绿素荧光（JIP测试参数）和820nm处的调制反射。在硫缺乏条件下，母叶依靠储存的储备来维持功能性PSII，但积累了减少的PQ池，减缓了PSII之后的电子流动。第一代子叶尽管具有较高的基线光合能力，但光合指标下降幅度最大（例如，相对电子传递速率下降约50%），水裂解复合体存在限制，PSI末端受体能力降低，导致电子传递的供体侧和受体侧瓶颈。最年轻的孙叶通过每个PSII吸收较少的光来避免这些瓶颈，通过替代途径引导电子以平衡PQ池和氧化还原稳定的PSI，同时将更多的碳转移到淀粉和花青素的生产中，两者的产量都提高了5倍。这些协调的、特定年龄的调整提供了反应灵活性，可能有助于维持菌落的光合功能，并在硫再次可用时促进快速恢复。
