Soil Temperature and Phosphorus Supply Interactively Affect Physiological Responses of White Birch to CO2 Elevation
Phosphorus (P) is an essential
element for some vital structural and metabolic functions of plants and its
deficiency can reduce energy transfer and even lead to a breakdown of cell membranes.
P deficiency can limit photosynthesis either indirectly by reducing the total
leaf area of a plant. And its supply and uptake by plants are strongly influenced by soil
temperature. However, the interactive effects of the two factors on the
physiological responses of plants to global change are poorly understood.
In this study, the authors examined how P supply and Tsoil interacted
in affecting physiological responses in white birch (Betula papyrifera)
to [CO2]. They exposed seedlings to 7°C, 17°C and 27°C Tsoil,
0.1479, 0.3029 and 0.5847 mM P2O5, and 360 and 720
μmol·mol-1 [CO2] for four months. Six seedlings per treatment combination were randomly selected for
measuring photosynthetic response curves to [CO2] after four months
of treatment. The authors have found that both the low soil
temperature and CO2 elevation resulted in photosynthetic down
regulation, but the specific mechanisms of the down regulation were different
between the two treatments, particularly the relative contributions of
biochemical and photochemical capacity, mesophyll conductance and sink strength
for carbohydrate utilization to the down regulation.
Furthermore, the data suggested that morphological adjustments, such as
reduced leaf size and total leaf area, were the primary form of responses in
white birch to low phosphorus supply and no significant physiological
acclimation to P supply was detected. The results suggest that white birch will
likely enhance water use efficiency under the projected future climate
conditions with doubled carbon dioxide concentration, particularly at warmer
soil temperatures. Although a trade-off between water use efficiency and
nutrient use efficiency is widely accepted, the results suggest that there does
not have to be a trade-off between the two, for instance, CO2 elevation
increased both use efficiencies and low soil temperature and reduced
nitrogen efficiency without affecting water use efficiency under elevated CO2.
Article by Gabriel
Danyagri and Qing-Lai Dang, from Lakehead University, Thunder
Bay, Ontario, Canada.
Full access: http://mrw.so/2Wyf8h
Image by Larry Krause, from Flickr-cc.
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