Photosynthetic Physiology and Clonal Growth of Solidago canadensis at Different Light Intensities:Implications for Invasive Mechanism

Understanding the eco-physiology and growth patterns of invasive plant is crucial to identify its invasive mechanism and formulate effective management strategy.Solidago canadensis,a noxious invasive plant throughout world including China,is able to invade into many habitats of various light intensities.To explore the invasive mechanism of this plant invader,we study its photosynthetic physiology and patterns of clonal growth in habitats of different light gradients.The results showed:that(1)The net photosynthetic rates,maximum net photosynthetic rates,light compensation point,light saturation point,and apparent quantum yield of S.canadensis declined with the decrease of light intensity.There was no significant differences among the photosynthetic physiological traits under highest light intensity(lx:50 000)and moderate light intensity(lx:30 000),while difference between moderate and low light intensities(lx:10 000),and between low light intensity and weak light intensity(lx:2 500)were significant.(2)The clonal growth(number of ramets(>15),number(>7)and length(>64 cm)of rhizome,diameter of rhizome(>0.59 cm))of S.canadensis under the high and moderate light intensities showed no significant differences,normally with more than 15 ramets and with very long rhizomes(usually >50cm).However,plants cultured under low and weak light intensities showed significantly decreased clonal growth,normally with only 2 ramets and much shorter(<17 cm)rhizomes.The plants in different light intensities also showed a different clonal architecture because the rhizomes changed greatly,plants in high and moderate light intensities had very long rhizomes and the plants were guerilla strategist,while the plants in low and weak light intensities had very short rhizomes and the plants grew in phalanx forms.This different clonal architecture greatly enhanced the plants’ability to adapt to various habitats of different levels of resources such as light intensity.Collectively,the results showed that S.canadensis was well adapted to habitats with high light intensity,and clonal growth and photosynthesis was inhibited under low and weak light intensities.However,its photosynthetic characters and clonal growth can maintained via plastic responses to a broad range of light intensities,which possibly facilitate its successful invasions in various habitats,including cropland,roadside and forest edge.