Do Various Conifers Respond Differently to Water Stress? A Comparative Study of White Pine, Concolor and Balsam Fir

Abstract

Aim of study: Two-year-old containerized balsam and concolor fir and one-year-old Eastern white pine transplants were grown under variable watering regimes with the goal of identifying plant morphological and some physiological traits under water stress. Area of study: This experiment was conducted in a greenhouse at the Tree Research Center on the Michigan State University campus, East Lansing, Michigan. Material and methods: Relative root collar diameter (RRCD), height growth (RHG), and root length (RRL) were measured as growth parameters. Stem water potential (Ψ), stomatal conductance (gs), net photosynthetic rate (Anet), intrinsic water use efficiency (iWUE=Anet/gs), foliar potassium (K+), and calcium (Ca+2) concentration were measured as physiological traits. Main results: Well-watered transplants had significantly higher RRCD, RHG, and RRL in fir species. Balsam fir and white pine transplants had a higher Ψ than concolor fir under severe stress. Fir species had higher Anet, gs, and a lower iWUE than white pine. White pine had a lower foliar K+ concentration, while balsam fir had the highest foliar Ca+2 concentration. Balsam fir had higher growth and Anet, gs, and iWUE under water stress due to their ability to maintain higher water uptake despite a reduced soil water content. Highlights: It is concluded that white pine has better drought tolerance because of the ability to withstand water stress through the mechanism of reduced photosynthetic activities and growth, minimize water loss, and increase water uptake.