Nutrient Foraging In Grapevine Rootstocks

The ability of grapevine rootstocks (101-14, 3309C, Riparia Gloire, St. George) and self grafted vine roots (Pinot noir, 115 clone) to exploit nutrient patches in soil was investigated in a low nutrient sandy loam soil. Rooted cuttings of vines were grown in 1.6–L pots with 4 different soil patches (50–mL plastic tubes that allowed root access through 1.5 mm window screen covered holes) enriched with either nitrogen, phosphorus, potassium, or a control (non-enriched) placed within each pot. Vines were harvested after 8 or 14 weeks and shoot dry matter and nutrient uptake were quantified. Roots growing within each ‘enriched patch’ were quantified and analyzed based on number and length of different root orders. Roots differed in their capacity to exploit nitrogen patches and phosphorus patches, but no differences among rootstocks were found in potassium or the control patches. Vines on 101-14 roots had higher numbers and lengths of all roots, and greater root weights in nitrogen patches, compared to all other rootstocks. Vines on their own roots had greater fine root length and total root weight than vines on St. George roots in phosphorus patches. Shoot dry mass and nutrient uptake were highest in vines grown on 101-14 roots, and lowest in self-rooted vines. The ability of roots to forage in the nitrogen enriched patch among rootstocks was highly correlated to shoot growth and nutrient uptake for most macro-elements. Although intrinsic differences in root characteristics (such as ratio of fine roots to woody roots, average root length in different classes, or average root diameter of fine roots) were found among different rootstocks, these characters did not clearly relate to root proliferation in the nitrogen patch or to shoot growth. Rather, it appears that the ability to sense and to stimulate root growth in the nitrogen enriched soil explains these findings.