PLANT PHYSIOLOGY , Vol 107, Issue 2 421-427, Copyright © 1995 by American Society of Plant Biologists
|
WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Dark Leaf Respiration in Light and Darkness of an Evergreen and a Deciduous Plant Species
R. Villar, A. A. Held and J. Merino
Departamento de Biologia Vegetal y Ecologia, Universidad de Sevilla, Apdo 1095, 41080 Sevilla, Spain (R.V., J.M.)
Dark respiration in light as well as in dark was estimated for attached
leaves of an evergreen (Heteromeles arbutifolia Ait.) and a deciduous
(Lepechinia fragans Greene) shrub species using an open gas-exchange
system. Dark respiration in light was estimated by the Laisk method.
Respiration rates in the dark were always higher than in the light,
indicating that light inhibited respiration in both species. The rates of
respiration in the dark were higher in the leaves of the deciduous species
than in the evergreen species. However, there were no significant
differences in respiration rates in light between the species. Thus, the
degree of inhibition of respiration by light was greater in the deciduous
species (62%) than in the evergreen species (51%). Respiration in both the
light and darkness decreased with increasing leaf age. However, because
respiration in the light decreased faster with leaf age than respiration in
darkness, the degree of inhibition of respiration by light increased with
leaf age (from 36% in the youngest leaves to 81% in the mature leaves).
This suggests that the rate of dark respiration in the light is related to
the rate of biosynthetic processes. Dark respiration in the light decreased
with increasing light intensity. Respiration both in the light and in the
dark was dependent on leaf temperature. We concluded that respiration in
light and respiration in darkness are tightly coupled, with variation in
respiration in darkness accounting for more than 60% of the variation in
respiration in light. Care must be taken when the relation between
respiration in light and respiration in darkness is studied, because the
relation varies with species, leaf age, and light intensity.
