Effect of Alternating Conditions of Boron Nutrition upon Growth and Boron Content of Grape Vines in Sand Culture

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Abstract
With controlled nutrients in sand-culture under greenhouse conditions, 2-yr.-old grape vines exhibited B-deficiency symptoms after 30 days from planting in sand without B in the nutrient soln. Initial symptoms of brownish water-soaked areas on young tendrils appeared on Catawba and Herbert vars., whereas diffuse yellowing of younger leaves was the first symptom with Golden Muscat. More advanced symptoms of B deficiency included cupping of leaves, short internodes, brittleness, misshapen leaves often with cut-leaf effects, dying of the terminal bud, and reduced amt. of growth. Basal leaves, matured during the first 30 days of growth, showed no deficiency symptoms at any time on B-deficient vines. However, B content of deficient vines became equalized to a common low level in all leaves and portions of the stem in contrast to the marked differences between leaves and stems in the vines well supplied with B as well as a gradient from apex to base. Addition of B to deficient vines after 7 weeks in sand culture resulted in resumption of normal new growth within 10 days, although older leaves with B deficiency symptoms did not change in appearance but did increase in B content. Omission of B in the nutrient was followed by deficiency symptoms within 25 days and by equalization of B content in the various plant parts. There was evidence of considerable translocation of B from mature leaves to meristematic portions of the vine when B was omitted from vines previously well supplied. Some indication was found that slower rate of growth preceded the earliest visual symptoms of deficiency. Although no critical level of B could be pointed out, owing to sampling variables, it is suggested that the equalization of B in the various parts of the vine in contrast to normal wide variations might be of diagnostic value.