Water relations in silver birch during springtime: How is sap pressurised?

• DOI: 10.1111/plb.12838
• Publication Date: 2018-05-07T03:59:19Z
• Authors: T. Hölttä; M. D. R. Domingue...; Y. Salmon; J. Aalto; A. Vanhatalo; J. Bäck; A. Lintunen
• Keywords: Osmotic pressure; Parenchyma; Transpiration stream

Positive sap pressures are produced in the xylem of birch trees boreal conditions during time between thawing soil and bud break. During this period, embolisms accumulated wintertime refilled with water. The mechanism for pressurization its environmental drivers not well known. We measured flow, pressure, osmotic concentration, whole stem diameter changes, root non-structural carbohydrate concentrations, along meteorological at two sites Finland after pressurisation period. diurnal dynamics pressure flow period varied, but were more often opposite to pattern burst, i.e. increased rate mostly decreased when temperature increased. Net conversion soluble sugars starch roots occurred Xylem was small comparison total it did follow changes or tree water relations. Based on these findings, we suggest that embolism refilling occur gradually over a few weeks through transfer from parenchyma cells vessels daytime, then nighttime by uptake soil. Possible discussed. Also functioning thermal dissipation probes changing content is