Water loss physiology and the evolution within the Tasmanian conifer genus Athrotaxis (Cupressaceae)

Abstract

The Tasmanian montane and rainforest conifer genus Athrotaxis provides a system for investigating the relationship between leaf form and function and its adaptive significance. The two species differ markedly in leaf size, shape, degree of imbricacy and stomatal distribution, whereas natural hybrid swarms and glasshouse-grown hybrid progeny are highly variable for these traits. In glasshouse-grown plants of the true species and a diverse hybrid progeny, stomatal conductance and density were strongly correlated, and varied by approximately 400% among individuals. Hybrids displayed lower stomatal densities and less discrimination of 13C than the true species, leading to a negative relationship between stomatal density and δ13C. In contrast with the highly variable stomatal densities and δ13C in glasshouse plants, field-grown plants were highly conservative in both characters. This, combined with relatively low stomatal density and high water-use efficiency in field-grown plants suggests optimisation of the trade-off between assimilation and water loss. Foliar conductance in the light for the hybrids and A.selaginoides was only 4–6 times as great as, and was strongly correlated with, conductance in the dark, suggesting incomplete stomatal closure or high cuticular conductance. Athrotaxis cupressoides was less ‘leaky’. This may reflect adaptation to its more exposed habitat.

Seasonal variability of the parameters of the Ball–Berry model of stomatal conductance in maize (Zea mays L.) and sunflower (Helianthus annuus L.) under well‐watered and water‐stressed conditions

“…While we know of no studies reporting a correlation between the BB g 0 and daytime g s values, Snyder et al () reported that the magnitude of true night‐time g s was correlated with the magnitude of daytime g s in multiple species. Correlations between nighttime and daytime g s have also been noted in conifers (Jordan, Brodribb, & Loney ) and in oak (Cavender‐Bares et al ).…”

Environmental stress and genetics influence night-time leaf conductance in the C4 grass Distichlis spicata

“…If separate regulation of g day and g night is possible it would imply that high g night is not necessarily linked to high g day . Strong, positive correlations between g night and g day have been observed among species (Snyder et al 2003;Jordan et al 2004) as well as among accessions of a single species (Christman et al 2008). The reason for the relationship is unclear, though suggested possibilities for the g day -g night relationship at least among accessions of a single species include factors such as stomatal size and density.…”

Is distribution of hydraulic constraints within tree crowns reflected in photosynthetic water‐use efficiency? An example of Betula pendula

“…In response to supplemental UV-B radiation (Gitz et al 2005) and drought stress (Monclus et al 2006), D S decreased leading to an increase in long-term or instantaneous WUE (ratio of A n to transpiration rate, A n /E). The inverse relationship between D S and foliar d 13 C accounts for variation in plant WUE among treatments and species in the conifer genus Athrotaxis (Jordan et al 2004). Ozone fumigation of olive plants had a greater effect on stomatal characteristics than on photosynthetic parameters, resulting in increased D S , and decreased stomatal aperture and A n /E (Minnocci et al 1999).…”