Leaf pigment contents in five tree and shrub species in A Mexican pineoak forest during periods of different water availability
2010
Himmelsbach, W. | González-Rodríguez, H. | Treviño-Garza, E.J. | Estrada, Castillón A.E. | Aguirre, Calderón O.A. | González-Tagle, M.A.
The objectives of this study were to describe, under sunny and shaded conditions, the seasonal dynamics of chlorophyll (a+b) and carotenoids content and the seasonal variations in predawn leaf water (Øwₚd) and osmotic potentials (Øₛₚd) of six native species co-existing in a mixed pine-oak forest, which undergo seasonal drought. All physiological variables, with exception of carotenoids content, were significantly different between sites, species and sampling dates. In general, values were higher under shaded conditions. Chlorophyll (a+b) content varied from 1.0 (Juniperus flaccida, under sunny) to 1.8 mg g⁻¹ (Quercus canbyi, under shaded). Carotenoids content ranged between 0.2 and 0.3 mg g⁻¹ for J. flaccida and Q. canbyi, respectively. Øwₚd varied between -0.47 (Q. canbyi under shaded) and -4.21 MPa (J. flaccid under sunny) and Øₛₚd between -1.47 (Acacia rigidula) and -3.79 MPa (Q. canbyi), both under sunny conditions. Hence, Q. canbyi achieved the highest leaf pigment contents at both sites. Thus, chlorophyll (a+b) content was significantly correlated (p<0.001) with air temperature (−0.70; J. flaccida) and relative humidity (−0.67; Pinus pseudostrobus), and carotenoids content with vapour pressure deficit (−0.60; J. flaccida) and averaged soil moisture content (−0.63; P. pseudostrobus). Furthermore, leaf chlorophyll (a+b) and carotenoids content were significantly correlated (p<0.01) to Øwpd (−0.43; P. pseudostrobus and -0.53; J. flaccida) and Øspd (−0.53; P. pseudostrobus and 0.58; J. flaccida), respectively. P. pseudostrobus and J. flaccida were at a physiological disadvantage during periods of drought in comparison to broad-leaved species such as A. rigidula, Arbutus xalapensis, Rhus virens and Q. canbyi, as they showed lower leaf pigment contents and were sensitive to environmental variables such as evaporative demands components (air temperature, relative humidity and vapour pressure deficit) and soil moisture content.
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