镉处理对植物-传粉者相互作用的影响

Effects of cadmium treatment on plant-pollinator interactions

植物、传粉者及其相互作用随环境改变而变化,但关于重金属污染土壤如何通过对植物的影响进而间接影响传粉者觅食行为仍缺乏系统研究.以辣椒为对象,采用盆栽实验方式,设置4个镉处理水平(0、2、4、8 mg/kg),比较植物性状(花性状和营养性状)和昆虫访花行为差异,并采用最优化模型方法揭示植物性状和昆虫访花行为变化的主要影响因素.结果表明:(1)相对于对照,中等浓度(4 mg/kg)的镉处理下辣椒花蜜体积显著增加(提高44.8%),高浓度(8 mg/kg)镉处理下花蜜浓度显著下降(降低21.0%).相对于对照,花朵数目和花冠直径均显著增加(分别提高18.3%和28.2%),而柱头长度显著降低(下降4.7%).花寿命呈下降趋势,但处理和对照间没有达到差异显著性水平;(2)辣椒的非结构性碳水化合物在中等浓度的镉处理下显著增加(相对对照提高25.8%),生物量随镉浓度的增加而显著下降(降低14.1%);(3)相对于对照,随镉浓度增加昆虫访花频率显著降低,下降30.0%;(4)随镉浓度的增加座果率均下降,但未达到差异显著性水平;(5)最优化模型结果表明非结构性碳水化合物显著影响辣椒的花蜜体积和花蜜浓度.花蜜体积和开花数目是昆虫访花频率最显著的影响因素.本研究结果表明镉处理引起花报酬数量和质量增加,但并没有提高昆虫访花频率.说明并不是丰富的花报酬资源都利于区域内传粉者种类和数量的维持,一旦花报酬中含有不利于传粉者生长发育的物质,传粉者数量和种类存在潜在的下降趋势.

Variations in floral traits that respond to environmental changes have been shown as correlating with pollinator foraging behavior.However,it is still unknown how cadmium stress affects floral traits and in turn influences pollinator foraging behavior.We conducted an experiment to explore the effects of cadmium stress on plant-pollinator interactions.Cadmium stress was administered at four levels(0,2,4,and 8 mg/kg).Our results demonstrated that the volume of nectar in flowers increased significantly after treatment with 4 mg/kg of cadmium,an increase of 44.8%compared to the treatment with 0 mg/kg.However,the concentration of nectar decreased significantly,by 21.0%,after treatment 8 mg/kg.Flower number and corolla diameter were significantly higher with the 0 mg/kg treatment compared to the others,increasing by 18.3%and 28.2%,respectively.Flower life span,however,decreased insignificantly by 4.7%with the treatments compared to the treatment with 0 mg/kg.Furthermore,cadmium stress significantly decreased the plant biomass and insect visitation rate(by 14.1%and 30.0%,respectively),but increased non-structural carbohydrates(by 25.8%)in Capsicum annuum leaves.There was an insignificant difference in fruiting rate among the cadmium treatments.Model selection results suggest that cadmium stress increase the volume and concentration of nectar;however,these variations decrease insect visitation rates.Our study shows that the abundance of flower rewards does not seem to be determined by pollinator species and density;Instead,heavy metals in nectar or pollen may adversely affect pollinator populations.