Physiological, stomatal and ultrastructural ozone responses in birch (Betula pendula Roth.) are modified by water stress

Abstract

The physiological, stomatal and ultrastructural responses to ozone and drought of ozone-sensitive and more ozonetolerant birch (Betula pendula Roth.) clones were studied singly and in combination, in a high-stress chamber experiment and in a low-stress open-field experiment. In the chamber experiment, well watered (WW), moderately watered (MW) or drought-stressed (DS) saplings were exposed for 36 d to 0 or 130 nmol mol ∠1 ozone. In the open-field experiment, well watered or drought-stressed saplings were grown for one growing season in ambient air or exposed to 1·8 × ambient ozone. Drought stress reduced growth rate, stomatal conductance, stomatal density and the proportion of starch and thylakoids in chloroplasts, but stimulated net photosynthesis, Rubisco and chlorophyll quantity at the end of the growing season, and increased the size and density of plastoglobuli. Ozone fumigations caused more variable, clone-and exposuredependent responses in growth, decreased stomatal conductance and net photosynthesis, an increased number of stomata, visible and ultrastructural chloroplast injuries, and enhanced autumn yellowing of the leaves. Ozoneinduced changes in plastoglobuli, starch and thylakoids resembled drought responses. The two experiments revealed that, depending on the experimental conditions and the variable, the response to drought and ozone stress can be independent, additive or interactive. Drought protected the plants from ozone injuries under high-stress conditions in the chamber experiment. In the low-stress, open-field experiment, however, enhanced ozone damage was observed in birch saplings grown under restricted water supply.

Morphological, physiological and anatomical traits of plant functional types in temperate grasslands along a large-scale aridity gradient in northeastern China

“…In the present study, stomatal densities of the five PFTs were not significantly correlated with water availability along the gradient; however, stomatal index in shrubs and perennial grasses decreased considerably with increasing aridity (Table 2). These findings are consistent with those of previous studies in which relative lower stomatal indexes were found to enable plants to minimize water loss through leaf transpiration and to increase water use efficiency4344. The significantly lower stomatal index in shrubs and perennial grasses under drought stress (File S3) underlie the two PFTs maintaining high capacity to regulate water loss by leaf transpiration.…”

Rubisco and some chaperone protein responses to water stress and rewatering at early seedling growth of drought sensitive and tolerant wheat varieties

“…Pelloux et al (2001) also noticed an increased quantitiy of RLS in Pinus halepensis M. subjected to drought stress. Pääkkönen et al (1998) detected an increase in Rubisco content under drought stress in Water deficit, as a result of osmotic stress, is expected to lead to increased protein aggregation and denaturation, making production of molecular chaperons more necessary (Zang and Komatsu 2007). According to Lawlor (2002) the decreased production of ATP in the chloroplasts of drought stressed plants serves as a signal triggering synthesis of chaperone molecules.…”

Ozone exposure affects leaf wettability and tree water balance

“…Patterns of stomatal density were not consistent in the literature. For example, increased stomatal density was reported for deciduous leaves exposed to ozone by Pääkkonen et al . (1998).…”