PS 57-115
What limits growth of vines under drought?
Growth and productivity of plants are limited by water availability. Climbing plants and vines in particular, combine some important traits of herbs (thin stems and leaves with high water content) and woody plants (long transport pathway of water from roots to leaves, vulnerability to cavitation). It is unclear how different processes (e.g. water uptake by roots, transport in xylem, stomatal regulation in leaves) may contribute to the overall limitation of productivity in these plants. We present first complex study focused on functioning of vine Humulus lupulus under water deficiency. Experimental plants were 2-3 m tall and grown in containers with regulated water supply. We measured the rate of transpiration, leaf water potential and the rate of net photosynthesis of hop plants in relation to water availability in soil. We also explored the anatomical traits of xylem in the stem. Finally, we analyzed potential limitations that structural and functional traits may represent in vines.
Results/Conclusions
We found anisohydric behavior of hop leaves with fluctuation of leaf water potential (WPL) in the range of -0.3 to -2.5 MPa. Diurnal fluctuation of WPL was greater under drought. We found that transpiration rate in ideal evaporative conditions was close to the rate of evaporation. Net photosynthesis decreased to 50% of its maximum when the water potential of leaves dropped to - 1.75 MPa, which indicates moderate sensitivity of leaves to water deficit. The transport capacity of stem for water was limited by embolism in the range 5 to 30%. Under normal conditions plants use only 30% of their maximum transport capacity in stem, hence the stem transport capacity is not limiting trait for water supply to leaves.