刈割对外来入侵植物黄顶菊的生长、 气体交换和荧光的影响

为明确不同刈割处理对黄顶菊生长和生理特性的影响,本研究在田间条件下,对黄顶菊在生长季内不同时间进行刈割处理。结果表明,刈割降低了黄顶菊植株各部分的生物量积累,其中以刈割3次效果最为显著,使黄顶菊总生物量、根生物量、茎生物量、叶生物量分别较对照下降82.57%、44.53%、80.04%、91.76%;植株的高度和花序数随刈割次数的增加显著降低,其中刈割3次的花序数为0;刈割1次植株分枝数最大,出现超补偿现象,刈割3次分枝数显著低于其他处理;叶绿素含量除了刈割2次出现增高趋势外,随刈割次数的增加,叶绿素含量逐渐降低;刈割处理使黄顶菊净光合速率(Pn)、气孔导度(Cond)和蒸腾速率(Tr)均显著升高;刈割3次的PSⅡ的最大光化学效率(Fv/Fm)和PSⅡ的潜在活性(Fv/F0)显著低于其它各处理,而初始荧光(F0)则显著增加;生长指标的可塑性指数大于生理指标可塑性指数,表明前者在黄顶菊对刈割处理等物理措施适应方面起到了更为重要的作用。总之,刈割3次处理黄顶菊的各项生长和生理指标所受影响最大,对黄顶菊植株的再生和开花结实抑制效果最为理想。

Effects of clipping on the growth, gas exchange and chlorophyll fluorescence of invasive plant, Flaveria bidentis

Flaveria bidentis,an exotic plant with the strong invasiveness,spreads at the most regions of Tianjin,Hebei,Province and Shandong Province,China,and there is an evidence that it has high potential to expand to other provinces.This article aims to find out an effective,economic and environmentally friendly measure to manage F.bidentis.Clipping is a common management measure to forage species,and proper clipping can promote their tillering and regeneration,thus enhancing their production yield and quality.However,excessive clipping may restrict the growth of aboveground part of forage species.High frequency clipping above the ground not only restrain plant growth,but also prevent the seed set.After 3 to 4 years′ consecutive clipping treatment,the plant would be killed eventually.There are many successful examples using the clipping measure to prevent and control invasive plants. A field experiment was carried out to clarify the effects of clipping measure on the growth and physiological characteristics of invasive plant F.bidentis,Sixty 3 m by 3 m plots were established.Four treatments(control,one-time clipping,two-time clipping and three-time clipping) were applied to the plots in completely randomized design. The results showed that clipping reduced the biomass accumulation of F.bidentis.Compared with the control,three-time clipping treatment was most efficient,and a reduction of 82.57%,44.53%,80.04% and 91.76% in total biomass,root biomass,stem biomass and leaf biomass was found respectively.The plant height and the inflorescence numbers decreased significantly with clipping times,especially under three-time clipping treatment,the inflorescence numbers declined to 0.The maximum branch numbers was recorded under one-time clipping treatment(so-called super-compensation phenomenon),while three-time clipping yielded the lowest branch numbers.Compared with control,chlorophyll content tended to decrease with increasing clipping times.In addition,clipping treatments significantly enhanced net photosynthetic(Pn),stomatal conductance(Cond) and transpiration rate(Tr).The maximum photochemical efficiency of photosystem Ⅱ(Fv/Fm) and potential activity of photosystem II(Fv/F0) under three-time clipping were significantly lower than other treatments,whereas initial fluorescence yield(F0) increased obviously.At same time,there was a trend of rise in parameters,such as net photosynthetic(Pn),stomatal conductance(Cond) and transpiration rate(Tr) upon clipping,In short,the impact of every growth and physiological index of F.bidentis was greatest by three clipping,three-time clipping affected growth and physiological indices of F.bidentis greatly,restricting its regeneration,flowering and eventually fructifying.The index of growth plasticity was higher than that of physiological plasticity,suggesting that growth plasticity was an important acclimation characteristic for clipping regimes for this invasive species. In practice,we suggest that the clipping measure should be adapted,combine with field replacement with clipping-resistance forage species such as Sorghum bicolor × S.sudanense,Dactylis glomerata,Medicago sativa,for wise management on F.bidentis.