Phloem and xylem formation as a function of tree vitality under drought stress

Response of tree growth and vascular tissue anatomy as a function of tree vitality under drought stress

Background

Hydraulic failure and carbon starvation have been postulated as the two main physiological mechanisms leading to tree mortality. Although hydraulic function and carbohydrate metabolism are strongly linked, little is known about the relationship between intra-annual dynamics of tree growth and the development of conducting tissues under drought (e.g., the timing of key phenological dates; duration; rate; anatomical changes).

Research focus

The main focus of the proposed study is to improve our understanding of the influence of drought stress on seasonal dynamics of phloem/xylem formation and structural characteristics of phloem/xylem cells of trees belonging to different vitality classes, i.e. trees before mortality versus healthy trees. In a broader sense, the focus of this PhD-study is to improve our understanding on the influence of drought on tree physiological processes (e.g., growth, sap flow, carbon allocation) and their effect on vascular tissue anatomy.

Approach and methods

Intra-annual dynamics of radial tree growth and phloem/xylem formation will be determined by point dendrometers and repeated cellular analyses of micro-cores, respectively. Changes in anatomical characteristics and intra-annual dynamics of phloem/xylem formation under drought will be analysed by light and electron microscopy (TEM, REM). Differences in content of non-structural carbohydrates (NSC) among trees will also be evaluated.

Time frame