Influence of Fertilization on Xylem Fluid Chemistry of Vitis rotundifolia Noble and Vitis Hybrid Suwannee

¹ Institute of Food and Agricultural Sciences, University of Florida Agricultural Research and Education Center, Monticello, FL 32344.

The influence of fertilization on the chemical profile of xylem exudate was determined during budbreak of Vitis rotundifolia (Michx.) Noble and Vitis hybrid Suwannee under laboratory and field conditions, respectively. Water flux from cut shoots of V. rotundifolia was affected 24 hours after soil applications of 3x Hoagland's solution (91 mM), (i.e., 2-fold increase compared to control). Maximum xylem fluid osmolarity was 21 mM despite soil treatments with 3x Hoagland's solution (91 mM). Although xylem fluid osmolarity was not influenced by fertilization, changes in the chemical profile did occur. Oxalic acid increased and malic acid, fructose and total sugars decreased in fertilized plants; amino acid concentrations were not altered. Application of fertilizer (i.e., 10N-4.3P-8.3K, plus micronutrients) to field-grown Vitis hybrid Suwannee did not alter water flux, xylem fluid osmolarity, and concentrations of organic acids, sugars, NH₄⁺, NO₃^-, P, K, Ca, Mg, Mn, Cu, Zn, and Cl in xylem exudate collected 21 days later. Fertilization resulted in substantial increases (60% to 150%) in the concentration of many amino acids including nitrogen-rich arginine and histidine. However, this was partially offset by a decrease in the concentration of amides (asparagine and glutamine) such that total amino acids was increased by only 15%. Xylem fluid chemistry appeared to be regulated largely by internal factors prior to the development of leaves.

Key words: amino acids, ammonia, macroelements, microelements, nitrate, organic acids, sugars, xylem fluid

Submitted on November 14, 1990