xylem Water 30 physiology 30 water 30 Plant Stems 24 Xylem 24 plant stem 24 article 22 Plant Leaves 20 metabolism 20 plant leaf 20 Argentina 18 Trees 16 hydraulic conductivity 16 tree 16 Droughts 12 Plant Stomata 12 Plant Transpiration 12 drought 12 evapotranspiration 12 plant stoma 12 stomatal conductance 12 wood 12 deciduous tree 10 Photosynthesis 8 Plant Roots 8 South America 8 Water relations 8 Wood 8 photosynthesis 8