Growth, morphology, and gas exchange in white spruce (Picea glauca) seedlings acclimated to different humidity conditions

Abstract

The study examined the effects of different relative humidity conditions at germination, early growth, and following cold storage on morphological and physiological characteristics of white spruce (Picea glauca (Moench) Voss) seedlings. Seedlings that were grown for 18 weeks following seed germination at the lower, 30% RH (RHinitial) treatments were shorter and had smaller stem diameters, shorter needles with more epicuticular wax, and a greater density of needles per centimetre stem, compared with the 80% RHinitial seedlings. After 18 weeks of growth under 30, 50, and 80% RH, the seedlings were hardened off, stored for 8 weeks at 3°C and planted in pots in growth chambers under 42 and 74% relative humidity (RHsubsequent). Under 74% RHsubsequent conditions, the lower RHinitial seedlings flushed sooner and had higher growth rates compared with the higher RHinitial seedlings. When the higher RHinitial seedlings were placed under 42% RHsubsequent conditions, their bud flush was delayed, and subsequent growth rates were lower compared with the lower RHinitial seedlings. When measured at 40% RH, seedlings subjected to lower RHinitial had higher net assimilation rates and stomatal conductance compared with the seedlings acclimated to higher RHinitial humidity. It was concluded that the humidity conditions present during early seedling growth following germination significantly affect their morphological and physiological characteristics during the second growth season.

Root temperature drives winter acclimation of shoot water relations in Cryptomeria japonica seedlings

“…Warming the whole plant by putting seedlings in a chamber would have changed air humidity and light quality as well as temperature when compared with the natural condition. Higher vapor pressure deficit could affect leaf characteristics, thereby increasing tolerance to higher evaporative demand (e.g., Roberts and Zwiazek 2001). However, because the effects of the whole-plant warming treatment diminished the seasonal change in shoot water relations, which was the opposite of that predicted, we consider that the observed change is solely the result of increased temperature.…”

Newly transplantedLarix olgensisHenry stock with greater root biomass has higher early nitrogen flux rate

“…Light was provided by a 125-W Phytolite TM plant growth lamp (Oudi Co., Huzhou, Zhejiang, China). The 18-h photoperiod has been considered sufficient for seedling active growth (Roberts and Zwiazek 2001), and PPFD from 100 to 150 μmol m -2 s -1 has been measured as the natural light characteristic for juvenile Changbai larch seedlings growing in forests (Zhu et al 2008). Every 3-4 d, all containers were rearranged randomly and the pH of the solution in each container was adjusted to 5.5-6.…”

Growth of European beech (Fagus sylvatica L.) saplings is limited by elevated atmospheric vapour pressure deficits

“…Nearly all of these studies focused on the effect of limited soil moisture while the consequences of elevated water vapour saturation deficits of the air (VPD) were not investigated. This is surprising because VPD has been found to have a significant and often large influence on plant growth and development of crop and horticultural plants (e.g., Ford and Thorne, 1974;Hoffman et al, 1971;Hoffman and Jobes, 1978;Tibbitts, 1979;Grange and Hand, 1987; Gislerö d and Mortensen, 1990;Marsden et al, 1996;Mortensen and Gislerö d, 2000;Roberts and Zwiazek, 2001;Leuschner, 2002;Codarin et al, 2006).…”