Fertilization and water stress interactions in young Eucalyptus grandis plants

CORINA GRACIANO; JUAN JOSÉ GUIAMET; JUAN FRANCISCO GOYA

CANADIAN JOURNAL OF FOREST RESEARCH

Año: 2006 vol. 36 p. 1028 - 1034

0045-5067

Water and nutrient availability interact in the control of tree growth. Fertilization can alter plant performance under drought by changing dry mass allocation to roots and leaves or the capacity for osmotic adjustment. The aim of this paper was to determine if fertilization with N and P affects water relations, and thereby water stress tolerance, in young Eucalyptus grandis plants. To assess if fertilization might enhance osmotic adjustment under drought, three-month old E. grandis plants were planted in pots and were fertilized either with N (1 g of urea) or P (12 g of calcium superphosphate). The soil was watered up to two soil water conditions: field capacity and –0.8 MPa. P-fertilization in well-watered conditions increased solute accumulation, which might confer a better performance under water stress. However, under water stress conditions, non-fertilized and N-fertilized plants made osmotic adjustment while P-fertilized plants did not. Moreover, P-fertilization increased dry mass allocation to leaves and decreased allocation to roots even under water stress conditions. N-fertilized plants increased allocation to roots and maintain allocation to leaves under water stress conditions in comparison with control plants, so they were affect by water stress not as much of P-fertilized plants. This may explain why P-fertilization increased growth when water was not limiting but it had no promoting effect under drought conditions. In the long term, the changes in dry mass allocation caused by P fertilization might increase the susceptibility to water deficit.   Keywords: osmotic adjustment, pressure-volume curves, water potential