川西南紫茎泽兰(Eupatorium adenophorum)旱季光合生理及其在四川盆地的入侵风险分析

Photosynthetic Ecophysiology of Crofton Weed During the Dry Season in the Dry Valley of Jinsha River and its Invasion Risks to Sichuan Basin

起源于墨西哥的紫茎泽兰是一种入侵我国云南和川西南等地危害极大的杂草.通过在金沙江干热河谷旱季对不同海拔和干旱程度的紫茎泽兰的光合作用进行原位观测和控制条件监测发现,紫茎泽兰光合作用旱季日变化方面具有典型的双峰曲线,光合作用抑制时间为14∶00-15∶00.干旱和高海拔可能提高紫茎泽兰叶片的净光合速率,水分利用效率亦随着干旱和海拔升高而提高,这表明紫茎泽兰对干旱河谷旱季干旱和高温环境的适应.同时,在叶面有效光合辐射(PAR)1,740μmol.m-2.s-1、叶面温度44℃的条件下仍然能够正常光合作用,并具有较高的净光合作用速率,显示出极高的抗高温和高光强胁迫能力,这些生理特点决定了紫茎泽兰比其它植物具有更大的光合作用优势和抗胁迫环境优势,从而决定其在营养生长竞争中对其它大多数植物的比较优势.紫茎泽兰净光合作用对叶面温度和光照强度的响应结果显示,紫茎泽兰光饱和点随着温度的升高而降低,最大净光合作用峰值在25℃至40℃之间,高温对紫茎泽兰光合作用有抑制作用,温度对光照有一定的补偿作用,这暗示紫茎泽兰潜在扩散区域气候特点是冬季具有较高光照或者较高温度或者二者同时具备,低温低光照不利于紫茎泽兰越冬和获得竞争优势.综上所述,紫茎泽兰在四川首要的潜在扩散区域和预防重点是横断山区中段和中北段干旱河谷地区(干暖和干温河谷)、川南宜宾和泸州各区县、以及盆地中部一些光热条件较好的局部区域.

Eupatorium adenophorum（also called crofton weed）,originating in Mexico,is a noxious non-native weed which has spread rapidly and endangered local ecosystem in the southwestern China,especially in Yunnan and Sichuan provinces.Monitoring of photosynthetic ecophysiological characteristics of crofton weed under natural and controlled conditions of microclimate has been conducted at different altitudes in the dry-hot valley of Jingsha River in the drought season.The results suggested that the photosynthetic diurnal variation of Eupatorium adenophorum generally presented typical double-peak curves and depressed during 14：00~15：00.However,the drought and high altitude may improve the photosynthesis net rate and the water use efficiency to a certain extent,which indicated the high adaptation of crofton to rigorous environmental factors stress of drought and high temperatures in dry season in this region.Meanwhile,Eupatorium adenophorum can still photosynthesize normally at relatively high photosynthesis net rate under leaf photosynthetically active radiation（PAR） of 1740 μmol·m-2·s-1 and the leaf temperature of 44℃,which implied that Eupatorium adenophorum was superior to some other plants in the aspects of highly efficient photosynthesis and resistance to environmental stress.The response of Eupatorium adenophorum photosynthesis to the leaf temperature and PAR showed that light saturation point decreased while the temperature got higher,and the peak of net photosynthesis rate is between 25℃~40℃.Temperature higher than 40℃ generally depressed photosynthesis of Eupatorium adenophorum,while higher temperature can also compensate for lower PAR to a great extent,which implied that the potential extending areas of E.adenophorum were relatively high solar radiation,or relatively high temperature,or both in winter climatically.Low radiation and temperature made against Eupatorium adenophorum to live through winter and get the competitive predominance over other native species.Therefore,the most possible regions of crofton weed invasion were the dry-hot valleys and dry-warm valleys located in middle and northern sects of Hengduan Mountains,and all counties of Yingbin and Luzhou in southern Sichuan,and some local areas with proper temperature and radiation in the central Sichuan basin as well.