Morpho-physiological responses of Nothofagus obliqua to light intensity and water status, with focus on primary growth dynamics

CRISTIAN TORRES; AMARU MAGNIN; SANTIAGO VARELA; MARINA STECCIONI; JAVIER GROSFELD; JAVIER PUNTIERI

TREES-STRUCTURE AND FUNCTION

SPRINGER

Lugar: Berlin; Año: 2018

0931-1890

Primary growth dynamics determine the number, spatial arrangement and time of differentiation of the leaves of tree axes, conditioning plant responses to environmental changes. By considering intra-individual variations related to axis differentiation in Nothofagus obliqua, we analyze the role of primary shoot growth dynamics in determining short-term responses to changes in environmental conditions. Before bud-break, saplings of N. obliqua were located in semi-controlled conditions, combining two light (full sunlight and shade) with two irrigation treatments (high and minimum water supply). Morphology, relative extension rate (RER) and leaf chlorophyll content were registered for the distal shoot arising directly from the trunk and for a distal shoot arising from a main branch. For the trunk shoot of plants of each treatment, we compared photosynthetic yield of proximal and distal leaves at the end of the growing season. Morphological responses varied depending on the axis category concerned, whereas leaf chlorophyll content presented low intra-individual variations. Shade conditions promoted higher RER, longer and more slender shoots, with longer internodes, and higher leaf chlorophyll content. Trunk shoots produced more nodes in well-watered conditions. Relay shoots were produced in full sunlight conditions, whereas shaded plants seem to produce neoformed leaves. Leaves of relay shoots tended to present slightly higher photosynthetic yield than proximal preformed leaves at the end of the growing season. Under shade and low water availability, distal leaves presented higher water use efficiency than proximal leaves. Additional leaves to those preformed could improve the acclimatation to the environmental conditions during shoot extension.