喀斯特土壤厚度和水分变化对两种菊科草本种子及果实的物候、可塑性和子代种子萌发率的影响（英文）

缺水的浅层土壤是植物在脆弱喀斯特地区生长和繁殖的关键限制因素。一年生草本植物是适应喀斯特地区严苛生境的先驱，但其繁殖策略对短缺水资源和有限土壤资源的双重限制响应尚不明确。因此，在这项研究中，我们通过评估果序和种子的数量、生物量和后代种子的发芽率，研究了两种一年生的菊科草本苍耳（Xanthium sibiricum）和三叶鬼针草（Bidens pilosa）在恶劣的喀斯特土壤环境中，种子和果实物候的可塑性和后代种子萌发率。苍耳和三叶鬼针草在完整的双向随机区组设计中，设置了三种土壤深度和三种水分梯度下生长。主要研究结果如下：（1）随着土壤厚度或（和）水分的降低，苍耳的子代数量（种子和果实）和生物量显著减少（P<0.05），三叶鬼针草在水分降低时增加果序和种子的生物量。（2）苍耳的亲本经历了资源减少后，种子数量和种子生物量没有相关性，而三叶鬼针草中种子数量和种子生物量之间存在显着的正相关（P<0.05）。（3）三种水分处理条件下，苍耳种子的萌发率没有随土壤厚度的减少而变化。对照条件下，随着土壤厚度的减小，三叶鬼针草的种子萌发率显著降低（P<0.05）。结果表明，苍耳倾向于通...

Seed and Fruiting Phenology Plasticity and Offspring Seed Germination Rate in Two Asteraceae Herbs Growing in Karst Soils with Varying Thickness and Water Availability

Shallow soil with low water availability is the key limiting factor for plant growth and reproduction in vulnerable karst regions. Annual herbs are pioneers adapted to these areas; however, little is known about the responses of their seeds and infructescence, and the germination of their offspring to these limited water and soil resources. In this study, we investigated how the seed and fruiting phenology plasticity and offspring seed germination rates of two annual Asteraceae herbs (Xanthium sibiricum and Bidens pilosa) respond to the harsh karst soil environment, by assessing the seed number, seed biomass and offspring seed germination rate. X. sibiricum and B. pilosa were grown under three soil thicknesses and three water availability levels in a full two-way randomized block design. The key results were as follows: (1) The number and biomass of progenies (infructescence and seeds) of X. sibiricum decreased with the decline of soil thickness and/or water availability (P <0.05). The infructescence and seed biomass of B. pilosa increased with the decline of water availability. (2) Seed quantity and seed biomass of X. sibiricum showed no correlation after their parents experienced resource reductions. A significant positive relationship between seed number and seed biomass was observed in B. pilosa (P <0.05). (3) The offspring seed germination rate of X. sibiricum did not change with the decrease of soil thickness under three levels of water treatment. However, the offspring seed germination rate of B. pilosa decreased significantly with the decrease of soil thickness under the control water level (P<0.05). The results show that X. sibiricum tends to improve its competitiveness by ensuring the quantity and quality of offspring in order to adapt to the shallow karst soils and dry karst habitats. In contrast, B. pilosa adapts to the unfavorable karst habitats by a risk-sharing strategy. B. pilosa produces more and bigger seeds to in an attempt to expand its survival range and escape from the unfavorable living environment, but this results in a lower seed number and germination rate of its progeny under the karst soil resource reduction.