根茎型植物扁秆荆三棱对光照强度和养分水平的生长响应及资源分配策略

自然界中光照和养分因子常存在时空变化,对植物造成选择压力。克隆植物可通过克隆生长和生物量分配的可塑性来适应环境变化。尽管一些研究关注了克隆植物对光照和养分因子的生长响应,但尚未深入全面了解克隆植物对光照和养分资源投资的分配策略。以根茎型草本克隆植物扁秆荆三棱(Bolboschoenus planiculmis)为研究对象,在温室实验中,将其独立分株种植于由2种光照强度(光照和遮阴)和4种养分水平(对照、低养分、中养分和高养分)交叉组成的8种处理组合中,研究了光照和养分对其生长繁殖及资源贮存策略的影响。结果表明,扁秆荆三棱的生长、无性繁殖及资源贮存性状均受到光照强度的显著影响,在遮阴条件下各生长繁殖性状指标被抑制。且构件的数目、长度等特征对养分差异的可塑性响应先于其生物量积累特征。在光照条件下,高养分处理的总生物量、叶片数、总根茎分株数、长根茎分株数、总根茎长、芽长度、芽数量等指标大于其他养分处理,而在遮阴条件下,其在不同养分处理间无显著差异,表明光照条件可影响养分对扁秆荆三棱可塑性的作用,且高营养水平不能补偿由于光照不足而导致的生长能力下降。光照强度显著影响了总根茎、总球茎及大、中、小球茎的生物量分配,遮阴条件下,总生物量减少了对地下部分根茎和球茎的分配,并将有限的生物量优先分配给小球茎。总根茎的生物量分配未对养分发生可塑性反应,而随着养分增加,总球茎分配下降,说明在养分受限的环境中球茎的贮存功能可缓冲资源缺乏对植物生长的影响。在相同条件下,根茎生物量对长根茎的分配显著大于短根茎,以保持较高的繁殖能力;而总球茎对有分株球茎的生物量分配小于无分株球茎,表明扁秆荆三棱总球茎对贮存功能的分配优先于繁殖功能。研究为进一步理解根茎型克隆植物对光强及基质养分环境变化的生态适应提供了依据。

Growth and biomass allocation responses to light intensity and nutrient availability in the rhizomatous herb Bolboschoenus planiculmis

In natural habitats, plants often experience selective pressure caused by temporal and spatial variation in light and nutrient availabilities, and clonal plants possess potential added capacity to respond to environmental changes via phenotypic plasticity and biomass allocation. Although many previous studies have focused on the effects of light and nutrient availability on plant growth and reproduction, few have explicitly tested for adaptive plasticity to resource allocation in clonal plants in response to light and nutrient levels. We conducted a greenhouse experiment on the rhizomatous, clonal plant Bolboschoenus planiculmis to investigate the effects of light intensity and nutrient availability on its growth, asexual reproduction, and resource storage strategies. The experiment incorporated two levels of light intensity (full daylight and shade) with four levels of nutrient availability (control, low, medium and high nutrient). Clonal growth, asexual reproduction, and resource storage were significantly decreased by shading. Plastic responses in the number and size of modules seemed to precede responses in biomass accumulation. Under full light, total biomass; number of leaves, rhizome ramets, and long rhizome ramets; total rhizome length; and length and number of buds were greater at the highest nutrient level than at the other three nutrient levels. Under shading, nutrient level did not affect these traits, indicating that low light intensity can constrain responses to different nutrient levels, and that high nutrient levels cannot compensate for lack of light. Allocation to total rhizomes, and to each of three size classes of corms was also significantly affected by light intensity. When light was limited, plants allocated less mass to rhizomes and large and medium corms but maintained allocation to small corms. Nutrient level did not affect allocation to total rhizomes, but the allocation to corms decreased with increasing nutrient availability, suggesting that the storage function of corms may serve to buffer the effects of nutrient shortage on future growth. Under the same conditions, the total rhizome biomass allocated more resources to long rhizomes than to short rhizomes to maintain a relatively high reproductive ability. Further, total corm mass allocated more resources to corms without ramets than to corms with ramets, suggesting that the storage function of the corm was given priority over its function in asexual reproduction. This study increases our understanding of the ecological significance of adaptive responses of rhizomatous clonal plants to environmental changes.