Functional Magnetic Resonance Microscopy of long- and short distance water transport in trees

Water transport in plants is one of the processes in the global water cycle that has a direct eect on climate and weather and supports plant growth. Water is absorbed byroots from the soil and is transported via the xylem to the leaves where it evaporates,the vapour diuses to the atmosphere via the stomata. This flux water vapour outof the leaf is accompanied by the diusion of CO2 into the leaf, a process driven by the photosynthetic xation of CO2 in the leaf (Sperry, 2004).

From 100 up to 1000 water molecules are lost per xed CO2 molecule (Maseda et al., 2006). Of all the water absorbed by plants, less than 5% remains in the plant for growth and storagefollowing growth. Transpiration by higher plants accounts for about one eight of allthe water evaporated to the atmosphere, or about three quarters of all water thatevaporates from land. Therefore, water transport in plants plays a signicant rolein the global water cycle (Sellers et al., 1997). The mechanisms of water uptake andtransport within the plant to the leaves and growing tissues and the means by which these fluxes are determined and regulated are still incompletely understood despite their evident importance to photosynthesis and growth and global water cycle.