Grapevine Rootstock Effects on Lime‐Induced Chlorosis, Nutrient Uptake, and Source–Sink Relationships

The experiment considered Vitis vinifera L. cv. "Pinot blanc" clone VCR5 grafted on a lime‐susceptible (3309 C) and a lime‐tolerant (41 B) hybrid rootstock and grown in 45 L pots of a calcareous and a non‐calcareous soil. Each treatment included plants bearing clusters and plants without clusters; in the latter case the bunches were removed 15 days before blooming. During the third growth year, shoot length, leaf chlorophyll (Chl), and mineral element concentrations were recorded. At the end of the growing cycle the grapevines were divided into leaves, shoots, berries, cluster stems, trunk, roots, and dry matter and mineral element composition per organ were analyzed. The 41 B rootstock showed its lime‐tolerance by exhibiting little reduction of shoot length when grown in the calcareous soil as compared to the non‐calcareous one, while 3309 C growing in the calcareous soil induced a dramatic shoot length reduction. The rootstock also affected the leaf chl concentration according to the known degree of lime‐tolerance/susceptibility: "Pinot blanc" grafted on 3309 C and growing on the calcareous soil showed chlorotic leaves while the plants grafted on 41 B had green leaves; cluster removal did not affect leaf chl. The fruit load (expressed as berry dry matter) was strongly affected by the soil and the rootstock; in the calcareous soil 41 B rootstock produced twice as high cluster dry matter than did 3309 C. A higher macronutrient uptake for the plants growing under lime‐stress conditions was affected by 41 B rootstock. Cluster removal in plants grown on calcareous soil produced different effects, as follows: in the case of 41 B rootstock, a redistribution of photosynthate to other sinks like shoot tip and roots occurred, while in the case of 3309 C only the roots benefited. Under lime‐stress condition the plants grafted on 41 B took up more iron (recorded as total amount in the leaves) than did those grafted on 3309 C.