Effects of wind on hydraulic properties and growth of Artemisia annua Linn

Wind is one of the most ubiquitous ecological factors affecting hydraulic properties,photosynthesis,mechanical properties and biomass distribution. In spite of more than two centuries of research,the response mechanism of plants to wind remains poorly understood. A major difficulty with understanding the effects of wind is that it affects both water balance by blowing the air and mechanical properties by wind drag. Yet it is uncertain that what patterns wind blowing influences stem hydraulic structure of plants. The relation between stem hydraulic structure and mechanical properties imposed by wind is rarely studied. Thus,study on comprehensive effects of wind on plants can contribute to understanding plant response mechanism under wind stress. In this study,Artemisia annua was used as material to evaluate the impacts of wind on plants.The wind-treated plants were blowed four hours everyday with wind speed of 5m / s for 60 days. We comparatively measured hydraulic properties,photosynthesis,mechanical properties of stem and biomass distribution of A. annua between wind blowing treatment and no wind control. The results showed that wind blowing significantly reduced midday twig water potential,and wind blowing significantly increased stem percent loss in conductivity( PLC),with PLC being 60.6% and44.3% for wind blowing treatment and control respectively. The maximum net photosynthetic rate and stomatal conductance of plants subjected to the wind were also reduced,which was only 62% and 55% of the control respectively. The height ofA. annua subjected to wind blowing was only 68% of the control at the end of the experiment,while the stem taper of wind blowing treatment was markedly higher than that of control. Total biomass was significantly decreased by the wind,with total biomass being( 44.0+ or - 6.03) g and( 32.8 + or - 7.01) g for control and wind blowing treatment respectively,while root / shoot ratio was significantly increased. However,flexural stiffness( EI) of treated plants was considerably higher compared to the control. Meanwhile,wind blowing reduced both stem vessel diameter and vessel density,with stem vessel diameter and vessel density being 77% and 55% as much as that of control respectively. Those results indicated that wind blowing limited the ability of plant hydraulic conductivity,leading to leaf water deficits through increasing cavitation embolism and decreasing the abality of hydraulic conductivity of stem,which limited plant photosynth