Inhaltszusammenfassung

The reactions of growth and water relations to drought were tested in young plants of four deciduous tree species (Fagus sylvatica L., Quercus petraea [Matt.] Liebl., Q. pubescens Willd., Sorbus aria [L.] Cr.) which occur at drought-caused tree-line sites in Central Europe on shallow calcareous soils. Two-year-old seedlings were planted into lysimeters and subjected to two periods (eleven and ten weeks, respectively) of severe drought, interrupted by thorough rewatering after the first drough...The reactions of growth and water relations to drought were tested in young plants of four deciduous tree species (Fagus sylvatica L., Quercus petraea [Matt.] Liebl., Q. pubescens Willd., Sorbus aria [L.] Cr.) which occur at drought-caused tree-line sites in Central Europe on shallow calcareous soils. Two-year-old seedlings were planted into lysimeters and subjected to two periods (eleven and ten weeks, respectively) of severe drought, interrupted by thorough rewatering after the first drought period. Control plants were always well watered. Drought stress responses of these plants were investigated by pV analysis, and by measurements of leaf conductance and actual water potentials. Additionally, desiccation experiments were performed with excised shoots of some of the trees. Drought-stressed F. sylvatica exhibited the highest rates of visible drought damage. However, this species was able to regain a high relative leaf water content (RWC) quickly after rewatering. S. aria, which can grow even on extremely exposed sites, was drought-adapted as shown by the following: its high leaf mass per unit area; its high leaf tissue elasticity; its high relative water content of saturated leaves (WCsat); and the low relative water content of its symplasm, which facilitates large changes in osmotic pressure in spite of low dry-mass related solute concentrations. High δ13C ratios (deviation of the leaf's 13C fraction from a standard) indicated a high long-term water-use efficiency by this species. These features allow an effective gas exchange even at low leaf water potentials. In contrast to F. sylvatica and S. aria, the Quercus species exhibited adaptability to drought, which was evident due to significant morpho-anatomical differences between the drought-stressed and control trees. In Q. petraea, adaptability was achieved by reductions in the leaf/root ratio, and in the number of second flushes and buds. In Q. pubescens, adaptability was found at the leaf level; this is indicated by larger differences between the osmotic pressures at full turgor and at turgor loss, in higher WCsat, and in a decrease in the RWC at turgor loss. These alterations are obviously due to changes in the leaf tissue properties. In none of the species was osmotic adjustment found as an adaptation to drought stress.» weiterlesen» einklappen

Autoren

Klassifikation

DFG Fachgebiet:
Pflanzenwissenschaften

DDC Sachgruppe:
Biowissenschaften, Biologie