外源硒对罗布麻幼苗生长及光合作用的影响

Effects of exogenous Selenium on growth and photosynthesis of Apocynum venetum L. seedlings

硒是植物生长发育的必需元素,能促进植物生长。采用盆栽试验的方法,研究了施用不同浓度的外源硒对一年生罗布麻幼苗生长及叶绿素荧光参数的影响。研究结果表明：根施（R）和叶面喷施（L）两种施硒方式下,硒浓度与罗布麻一年生幼苗生长及叶绿素荧光参数有极显著相关性,表现为,一定浓度范围内（0-1.5 mg·kg^-1）,随着硒浓度的增加,罗布麻茎干重、叶干重、株高、茎粗、主叶对数和侧枝数均有有不同程度的上升;Fv/Fm、Fv/Fo、Ψo、φEo、PIABS、均随着施硒浓度的增加而增加;VK、VJ、VI均随着施硒浓度的增加而逐渐下降,Sm逐渐上升;说明施硒促进了罗布麻叶PSII的活性,提高了PSII反应中心的开放程度,增大其光能利用率。但随着供应浓度的进一步提高,各项生长及荧光指标有所降低,因此过量的硒供应对于罗布麻生长不利,而且有益与有害之间的范围很小,具体罗布麻栽培中要严格控制硒用量在1-3 mg·kg^-1范围内。

Selenium is a necessary element for plant growth. This study employed the method of pot experiments to investigate the effect of exogenous selenium concentration on the growth of annual seedlings and chlorophyll fluorescence parameters of Apocynum venetum L. The results showed that annual A. venetum L. seedling growth and chlorophyll fluorescence parameters had significant correlation under root applied Selenium（R） or spray Selenium of A.venetum L. Within a certain range of concentration（0-1.5 mg·kg^-1）,stem dry weight,weight,plant height,stem diameter,the number of leaves of A. venetum L. on the stem and branches increased significantly with the increase of selenium concentration. Fv/Fm,Fv/Fo,Ψo,φEo,PIABS also increased with the increase of selenium concentrations while VK,VJ,VIgradually decreased. However,the growth and chlorophyll fluorescence parameters of Apocynum venetum L. reduced with the excessive supply of selenium. Selenium promoted the growth of Apocynum,particularly the function of the root system,which reinforced the nutrient absorption ability of the plant. Although high concentration（3-5 mg·kg-1）of selenium put stresses on the aboveground parts of the plant,it could still boost the growth of the root. There might be two reasons why the root can grow fast under the high concentration. On the one hand,the root might have a better tolerance to selenium toxicity than the rest parts of the plant. On the other hand,it was possible that A. venetum L. had had developed an adaptive response to selenium poisoning. A. venetum L. could change the growth strategy to let more photosynthetic product and nutrients being allocated to roots,to increase root cap ratio and to improve the absorbing ability to maintain the normal growth. A certain concentration of selenium can improve the activity of PSII and increase the PSII reaction central open degree,and then improve the utilization rate of light energy,so as to effectively promote the growth of A. venetum L.. The suitability range of selenium concentration was not obvious. The concentration below 1 mg·kg^-1had no significant influence on the growth of A. venetum L. but the concentration greater than 3 mg·kg^-1would significantly inhibit the growth of the plant. Therefore,concentration of selenium should be strictly controlled within 1-3 mg·kg^-1to avoid the accumulation of selenium in the soil. Leaf spray might be a better harmless way to improve the growth of the plant.