Soil temperature and intermittent frost modulate the rate of recovery of photosynthesis in Scots pine under simulated spring conditions
Soil temperature and intermittent frost modulate the rate of recovery of photosynthesis in Scots pine under simulated spring conditions
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DOI：
10.1111/j.1469-8137.2007.02273.x
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发表时间：
2008-01-01
期刊：
影响因子：
9.4
通讯作者：
Lloyd, Jon
中科院分区：
文献类型：
--
作者：
Ensminger, Ingo;Schmidt, Lilian;Lloyd, Jon
随着气候变暖，北方森林树木春季光合作用的开始时间较早，但土壤与空气温度对春季恢复的重要性仍有待确定。在人工控制的环境条件下，研究了不同土壤和气温条件对樟子松（Pinus sylvestris）幼苗光合作用春季恢复的影响。以冬季驯化的樟子松幼苗为材料，将其转移到不同的模拟春季条件下，跟踪光合作用的响应。与对照相比，低温或冻土处理的幼苗光合电子传递和净CO2吸收的恢复速率较慢。此外，吸收的大部分光没有被光化学利用，而是通过叶黄素循环色素热消散。间歇性霜冻事件降低光合能力，增加热能耗散。霜冻后的几天内，光合能力恢复到霜冻前的水平。春季条件下18 d后，间歇性霜冻处理的幼苗与对照植物的最佳光合量子产量没有差异。这些结果表明，如果气温保持有利且冰点以下气温持续时间较短，间歇性霜冻事件会延迟但不会严重抑制春季万年青针叶树光合作用的恢复。冷和/或冻结的土壤施加更强的抑制作用的恢复过程中，但他们并不完全抑制它。
An earlier onset of photosynthesis in spring for boreal forest trees is predicted as the climate warms, yet the importance of soil vs air temperatures for spring recovery remains to be determined. Effects of various soil- and air-temperature conditions on spring recovery of photosynthesis in Scots pine (Pinus sylvestris) seedlings were assessed under controlled environmental conditions.Using winter-acclimated seedlings, photosynthetic responses were followed after transfer to different simulated spring conditions.Recovery rates for photosynthetic electron transport and net CO2 uptake were slower in plants from cold or frozen soil compared with controls. In addition, a greater fraction of light absorbed was not used photochemically, but was dissipated thermally via xanthophyll cycle pigments. Intermittent frost events decreased photosynthetic capacity and increased thermal energy dissipation. Within a few days after frost events, photosynthetic capacity recovered to prefrost levels. After 18 d under spring conditions, no difference in the optimum quantum yield of photosynthesis was observed between seedlings that had been exposed to intermittent frost and control plants.These results show that, if air temperatures remain favourable and spells of subfreezing air temperatures are only of short duration, intermittent frost events delay but do not severely inhibit photosynthetic recovery in evergreen conifers during spring. Cold and/or frozen soils exert much stronger inhibitory effects on the recovery process, but they do not totally inhibit it.