Location of hydraulic resistance in the soil–plant pathway in seedlings of Pinussylvestris L. grown in peat

Abstract

Seedlings of Pinussylvestris L. were grown in three different soil media: 100% peat, 40% silt–60% peat, and 60% silt–40% peat. The percentages refer to total dry weight. Needle conductance, needle water potential, and plant water conductance were measured at different levels of soil water potentials controlled with a semipermeable membrane system. Seedlings grown in the 60:40 silt–peat mixture had a plant water conductance at a soil water potential of −0.1 MPa 3 times that of seedlings grown in pure peat. In an experiment where the roots were dipped in a silt slurry before planting, it was found that the plant water conductance at low soil water potential (−0.1 MPa) increased more than 2 times compared with undipped controls. We concluded that an important resistance to water flow in the soil–plant pathway was located in the soil outside the roots and probably was the most important resistance in the root–soil interface. The use of low humified peat as a growth medium is open to discussion from a silvicultural point of view because of its hydraulic properties under dry conditions.

Gas exchange and water relations of 3 sizes of containerized Picea mariana seedlings subjected to atmospheric and edaphic water stress under controlled conditions

“…The wet portion of that range is similar to tensions measured in planting areas normally targeted for black spruce (eg, Bernier, 1993 (Örlander and Due, 1986;Bernier, 1992 (Stewart et al, 1995). Instead, the parallel drop in P n and g sW suggests a common mechanism of regulation.…”

Performance and physiology of large containerized and bare-root spruce seedlings in relation to scarification and competition in Qu�bec (Canada)

“…Available soil water, root system characteristics (size, distribution, and hydraulic conductivity), and root-soil contact influence the seedling's ability to take up water [15]. For example, for containerized Scots pine [Pinus sylvestris L.] seedlings, the most important resistance to water-flow in the soil-plant pathway is located in the peat soil surrounding the roots [42]. Bernier [4] and Bernier et al [5] also reported low soil hydraulic conductivity of peat-based growing medium under low soil water content conditions and its effect on seedling water stress.…”

Influence de la présence de racines adventives et du continu en eau du substrat sur l échange gazeux la croissance et l allocation glucidique chez les semis d épinette noire (Picea mariana (Mill ) B S P )

“…Chaque point correspond à la moyenne de "n" mesures ( les épinettes noires avaient donc formé un système racinaire entièrement nouveau. La formation de ces nouvelles racines adventives permettrait l'ancrage à long terme du plant ainsi que l'absorption de l'eau et des minéraux à la surface du sol, ce qui est très important pour la survie des semis (Sutton 1987, Tang et Kozlowski 1983, Topa et McLeod 1986, Burdett 1990, Coutts et al 1990, Megonigal et Day 1992 Lors de la plantation de semis de conifères, le stress hydrique est la première cause de mortalité ou de baisse de croissance (Kramer 1986, Ôrlander et al 1986, Burdett 1990). Un stress hydrique causé par la transplantation peut être dû au confinement des racines au trou de plantation, au mauvais contact des racines avec le sol ou à la faible perméabilité des racines (Sands et al 1984, Burdett 1990, Jiang et al 1994.…”