涝渍对3个树种生长、组织孔隙度和渗漏氧的影响

为了了解落羽杉(Taxodium distichum)、乌桕(Sapium sebiferum)和美国山核桃(Carya illinoensis)等树种的耐涝机制, 采用盆栽模拟涝渍环境的试验方法, 设置了淹水、渍水和对照3个处理, 测定了一年生落羽杉、乌桕和美国山核桃实生苗的生长、组织孔隙度、根氧消耗等指标。结果表明, 涝渍处理抑制了落羽杉、乌桕和美国山核桃的生物量和生物量增量(渍水处理下落羽杉的生长得到了促进), 增加了3树种的根冠比, 从生物量和生物量增量下降幅度来评价, 落羽杉的耐涝性最强, 其次为美国山核桃。淹水和渍水处理下, 落羽杉、乌桕和美国山核桃的根、茎和叶中的组织孔隙度显著增加, 且随着处理时间的延长, 各器官的组织孔隙度有增加的趋势, 3个树种中, 落羽杉的根、茎和叶中的组织孔隙度均较其他2个树种高。淹水和渍水处理下, 移除茎明显增加了落羽杉、美国山核桃和乌桕的根的氧消耗, 表明涝渍处理增强了O₂在3个树种体内的运输并通过根系扩散到涝渍土壤中的能力, 并且随着处理时间的延长, 3个树种体内运输O₂并扩散到土壤中的能力有逐渐增强的趋势。因此, 涝渍环境总体上抑制了落羽杉、乌桕和美国山核桃等树种的生长, 但各树种为了适应这种生长环境, 形成了大量的通气组织, 从而导致各器官组织孔隙度的增加, 增强了O₂通过植物体运输到根系并扩散到土壤中的能力, 解决了根系及根际缺氧的矛盾。

Effects of waterlogging on growth, porosity and radial oxygen loss of three tree species

Aims Flooding reduces soil oxygen content, and leads to oxygen deprivation in the root system of plants. Since oxygen is essential for mitochondrial respiration, this process cannot be maintained under anoxic conditions and must be replaced by other pathways. Our objective was to understand flooding adaptation mechanisms of baldcypress (Taxodium distichum), Chinese tallow tree (Sapium sebiferum) and pecan (Carya illinoensis) under waterlogged conditions.
Methods One-year seedlings of baldcypress, Chinese tallow tree and pecan were grown in pots, and three treatments were implemented: CK (control, common soil water content), WA (waterlogging, water level equal with soil surface) and FL (flooding, water level 8 cm above soil surface). Treatments lasted 65 days, and indexes of growth, porosity and root oxygen consumption were determined at different times after treatment.
Important findings We found that WA and FL treatments inhibited growth of both Chinese tallow tree and pecan, but biomass and biomass increment of baldcypress increased under WA condition, indicating that baldcypress was more tolerant to flooding. Root/shoot ratio of the three tree species increased significantly under WA and FL treatments, which was primarily due to the decrease of stem and leaf biomass. WA and FL treatments also stimulated aerenchyma formation in the roots, stems and leaves of the three tree species, thereby the porosity in the roots, stems and leaves of the three tree species increased significantly under WA and FL conditions. The aerenchyma formation and increased porosity enhanced O₂ diffusion to roots and rhizosphere. Our results indicate that baldcypress, Chinese tallow tree and pecan exhibit several adaptive mechanisms in response to waterlogging, including formation of new roots, aerenchyma formation, increased porosity of the roots, stems and leaves, and increased O₂ release into the rhizosphere.