EFFECTS OF DROUGHT OR FLOODING STRESSES ON PHOTOSYNTHESIS XYLEM FLUX AND STEM RADIAL GROWTH

Walnut tree (Juglans regia) is highly sensitive to environmental stresses. Changes in water regime, either abundance and shortage, affect the physiological parameters of the growth. From visible morphological point of view the two stresses seem to have the same answers: wilting and epinastic leaves appear in trees subjected to both stresses. This is accompanied to the reduction of leaf gas exchange. The stresses caused the block of xylem water transport in few hours in flooding condition and with progressively reduction in drought condition, consequence of soil water depletion. Furthermore, also the total stem radial growth, index of cambial activity, is blocked and small stems shrinkage is evident. When stresses are removed the damage remain present in tree subjected to root hypoxia, senescence and fall of leaves occurred; and after time if new buds begin to expand to give new shoot xylem water transport is resumed but without any recovery of radial growth. On the other hand, in drought stressed trees few hours are enough to observe recovery of water transport, radial growth, and carbon dioxide assimilation. The results put evidence of strong deleterious effect of root hypoxia on tree physiology and growth, consequence of metabolic root status.

IV International Walnut Symposium

V. Belloni, S. Mapelli

stem radial growth, water stress, flooding, walnut

https://doi.org/10.17660/ActaHortic.2001.544.43