Growth and transpiration of Japanese cedar (Cryptomeria japonica) and Hinoki cypress (Chamaecyparis obtusa) seedlings in response to soil water content

Abstract

To investigate the effects of soil water content on growth and transpiration of Japanese cedar (Cryptomeria japonica D. Don) and Hinoki cypress (Chamaecyparis obtusa (Siebold et Zucc.) Endl.), potted seedlings were grown in well-watered soil (wet treatment) or in drying soil (dry treatment) for 12 weeks. Seedlings in the wet treatment were watered once every 2 or 3 days, whereas seedlings in the dry treatment were watered when soil water content (Theta; m3 m(-3)) reached 0.30, equivalent to a soil matric potential of -0.06 MPa. From Weeks 7 to 12 after the onset of the treatments, seedling transpiration was measured by weighing the potted seedlings. After the last watering, changes in transpiration rate during soil drying were monitored intensely. The dry treatment restricted aboveground growth but increased biomass allocation to the roots in both species, resulting in no significant treatment difference in whole-plant biomass production. The species showed similar responses in relative growth rate (RGR), net assimilation rate (NAR) and shoot mass ratio (SMR) to the dry treatment. Although NAR did not change significantly in either C. japonica or C. obtusa as the soil dried, the two species responded differently to the dry treatment in terms of mean transpiration rate (E) and water-use efficiency (WUE), which are parameters that relate to NAR. In the dry treatment, both E and WUE of C. japonica were stable, whereas in C. obtusa, E decreased and WUE increased (E and WUE counterbalanced to maintain a constant NAR). Transpiration rates were lower in C. obtusa seedlings than in C. japonica seedlings, even in well-watered conditions. During soil drying, the transpiration rate decreased after Theta reached about 0.38 (-0.003 MPa) in C. obtusa and 0.32 (-0.028 MPa) in C. japonica. We conclude that C. obtusa has more water-saving characteristics than C. japonica, particularly when water supply is limited.

Adaptive diversity in Castanea sativa Mill. half-sib progenies in response to drought stress

“…An increase in root:shoot ratio is a common observation under water stress since drought inhibits growth of the stem more severely than that of the root (Saab et al, 1990), and biomass distribution changes in response to the water content of the soil (Nagakura et al, 2004). In our study, the relationship AB/RW showed a common general tendency for all families, with lower values in those plants subjected to drought stress.…”

“…In our study, the relationship AB/RW showed a common general tendency for all families, with lower values in those plants subjected to drought stress. Low values of this parameter are associated with resistance to periods of drought (Nagakura et al, 2004;Villar-Salvador et al, 2004;Yin et al, 2005), indicating a greater investment in root biomass and hence an increased capacity to absorb water from the soil. These changes in the relationship are of great interest in studies of drought tolerance in woody species (Bernier et al, 1995;Farrell et al, 1996) and are regarded as an acclimatization mechanism to avoid dehydration (Guan et al, 2004;Yin et al, 2005).…”

An analysis of ecophysiological responses to drought in American Chestnut

“…This increase in water use efficiency, found in the gas exchange response to water stress, is attributed to the greater decrease in g s as opposed to A net under glasshouse or field environmental conditions. Others (e.g., [27,37]) have reported a similar water use efficiency response in deciduous and conifer species. Although we were able to achieve more negative Ψ p than the Abrams et al [2] study, Table IV compares our WUE i values to those of other co-occurring species at similar Ψ p values.…”

Stomatal conductance and transpiration of co-occurring seedlings with varying shade tolerance

“…Intra-and interspecific differences of E in saplings and mature trees have been well documented in the field and provide a clear picture of microclimate and physiological influences on water loss, including responses to radiation, humidity, air temperature, and soil water deficit (Mott and Parkhurst 1991;Granier et al 2000;Bowden and Bauerle 2008;Herbst et al 2008). In contrast, seedling E has traditionally been observed under manipulated settings, either in greenhouse conditions (Holmgren 2000;Nagakura et al 2004;Baquedano and Castillo 2006) or in the field under an abbreviated range of microclimate variables (Wang et al 2006). A controlled experimental setup provides a method of documenting specific microclimate influences and insures seedling survival, but fails to adequately demonstrate the entire array of meteorological forcings experienced by the seedling in reality.…”