氟离子和碳酸氢根对构树幼苗生长和碳代谢的影响

Effects of Fluoride and Bicarbonate on Growth and Carbon Metabolism of Broussonetia papyrifera Seedlings

【目的】通过研究氟离子和碳酸氢根添加对构树幼苗生长和碳代谢的影响,探讨喀斯特生态区域内的氟离子对植物光合作用和糖代谢过程的影响机制,以期为氟富集地区的森林植被管理和修复提供理论依据。【方法】以喀斯特适生植物构树幼苗为研究对象,通过在Hoagland营养液中加入NaF和NaHCO_(3)制成处理液。试验共设置4个处理组,即对照组、3 mmol·L^(-1)NaF处理组、3 mmol·L^(-1)NaHCO_(3)处理组和3 mmol·L^(-1)NaF+3 mmol·L^(-1)NaHCO_(3)处理组。测定构树幼苗在处理条件下的生长指标、光合指标、磷酸果糖激酶(PFK)活性、葡萄糖-6-磷酸脱氢酶(G6PDH)活性和碳酸酐酶(CA)活性。【结果】1)F^(-)添加显著抑制了构树幼苗的生长和光合能力,并且使葡萄糖代谢从糖酵解途径转移到磷酸戊糖途径。在不同时添加HCO^(-)_(3)的情况下,F^(-)对叶片内的CA酶活性不产生显著影响,但在同时添加HCO^(-)_(3)时,F^(-)显著抑制叶片内的CA酶活性。2)根际HCO^(-)_(3)添加能够显著促进构树幼苗的生长和光合能力,提高葡萄糖代谢总量和CA酶活性。而同时添加F-能抑制HCO^(-)_(3)添加对植株产生的正面效应,使植株的生长、光合、葡萄糖代谢总量都显著下降,而G6PDH酶活性显著上升。【结论】环境中较高浓度的F-能够显著抑制构树的生长,具体体现在对光合过程的抑制和把过多的糖代谢底物分配到PPP途径上。而在根际添加适量的HCO^(-)_(3)能够为植株的生长提供额外的光合代谢底物,提高植株的糖代谢水平,从而对植物的抗逆性和生长都产生有利的影响。在同时添加HCO^(-)_(3)和F-条件下,HCO^(-)_(3)对植物生长的增益效果被F-的作用所削减,这主要是因为F-对植物光合系统中各种酶结构和活性的破坏和抑制作用,也可能与F-和HCO^(-)_(3)在根系吸收时存在竞争关系有关。

【Objective】The study was aimed to investigate the effects of fluoride and bicarbonate on the growth and carbon metabolism of Broussonetia papyrifera seedlings,and to reveal the mechanism of the effects of fluoride ions on plant photosynthesis and sugar metabolism in karst ecological region,in order to provide a theoretical basis for forest vegetation management and restoration in fluorine rich areas.【Method】B.papyrifera seedlings were treated with Hoagland nutrient solution added with NaF and NaHCO3 in 4 ways:control,3 mmol·L^(-1)NaF,3 mmol·L^(-1)NaHCO_(3) and 3 mmol·L^(-1)NaF+3 mmol·L^(-1)NaHCO_(3).The growth parameters,photosynthetic parameters,phosphofructokinase(PFK),glucose-6-phosphate dehydrogenase(G6PDH)and carbonic anhydrase(CA)enzyme activities of B.papyrifera seedlings were measured.【Result】1)Addition of F-significantly inhibited the growth and photosynthetic capacity of plants,and transferred glucose metabolism from glycolysis pathway to pentose phosphate pathway.When HCO^(-)_(3)was not added at the same time,F-had no significant effect on CA activity in leaves;but when HCO^(-)_(3)was added at the same time,F-significantly inhibited CA activity in leaves.2)Rhizospheric HCO^(-)_(3)significantly promoted plant growth and photosynthetic capacity,increased total glucose metabolism and CA enzyme activity.However,F^(-)inhibited the positive effects of HCO^(-)_(3)on plants,consequently significantly reduced growth,photosynthesis and glucose metabolism,but significantly increased G6PDH activity.【Conclusion】In conclusion,the higher concentration of F^(-)in the environment significantly inhibits the growth of B.papyrifera seedlings,and its adverse effects on the growth of B.papyrifera are reflected in the inhibition of photosynthetic process and the distribution of excessive carbohydrate metabolic substrates to pentose phosphate pathway.The appropriate amount of rhizospheric HCO^(-)_(3)provides additional photosynthetic metabolic substrate for plant growth,and improves the glucose metabolism level of plants,which improves the stress resistance and growth ability of plants.Under the HCO^(-)_(3)and F-treatment,the favorable effect of HCO^(-)_(3)on plant growth was reduced by F-,mainly due to the destruction and inhibition of the structure and activity of various enzymes in plant photosynthetic system,and it may also be related to the competition between HCO^(-)_(3)and F-during root absorption.