The Influence of Phosphorus Availability and Rootstock on Root System Characteristics, Phosphorus Uptake, Phosphorus Partitioning, and Growth Efficiency

¹ Duarte Nursery, Inc., 1555 Baldwin Road, Hughson, California 95326
² Dept. of Viticulture and Enology, University of California, Davis, CA 95616-4780

Chenin blanc grapevines on either Freedom or St. George rootstock were grown under sufficient (+P) and deficient (-P) soil phosphorus availability. Root system morphology was similar for both rootstocks regardless of P availability. Vines on Freedom accumulated more P than did vines on St. George, especially under -P. There was a marked decrease in the amount of P translocated to the shoot and accumulated in the petioles of vines on St. George with decreasing P availability. Also, vines on Freedom produced more shoot growth per unit P than did vines on St. George, particularly under -P, although P use efficiency for overall vine growth was not influenced greatly by rootstock. Differences in P uptake, translocation, and growth efficiency may account for differences in shoot growth inhibition between vines on St. George and Freedom observed in our earlier study. Vines on the different rootstocks partitioned different amounts of P into petioles under +P, but not under P-deficient conditions.

Key words: Vitis, grapevines, rootstock, phosphorus, root growth, root morphology, phosphorus uptake, phosphorus partitioning, growth efficiency, Chenin blanc, Freedom, St. George

Submitted on February 1, 1995