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  • Author or Editor: Lloyd A. Peterson x
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Abstract

Table beet (Beta vulgaris L.) cultivars (‘Ruby Queen’, ‘Gladiator’, and ‘Mono-King Explorer’) grown with varying B regimens had similar patterns of dry weight and B accumulation. Between 0.1 and 0.4 ppm B in solution, dry weight of leaf blades, petioles, roots, and fibrous roots did not increase. Boron content increased in leaf blades and remained constant in other plant parts. From 0.0005 to 0.011 ppm B in solution, dry weight of whole plants, shoots, and roots increased through 0.007 ppm B. Boron content increased in shoots and leaf blades through 0.011 ppm B. Distribution of dry weight and B content was reversed in these plants compared to those grown in B levels sufficient for normal development. With insufficient B levels, plants accumulated greater dry weight in shoot than root portions, and B content was greatest in root compared to shoot portions. The effect of short-term B stress on dry weight and B content varied with the growth stage at which stress was induced. Severity of B deficiency symptoms was related to length of the B stress interval. Blackheart injury of roots occurred in plants stressed during early secondary growth. Recovery from stress was associated with B stress induced prior to or after this critical developmental period.

Open Access

Ammonium and NO3 uptake from hydroponic solutions containing 1 mm each of (NH4)2SO4 and Ca(NO3)2 were measured during development of Dendranthema ×grandiflorum (Ramat.) Kitamura `Iridon', `Sequoia', and `Sequest'. Nitrogen depletion from solutions approximated a 1 NH4: 1 NO3 ratio throughout a 90-day growth cycle (r = 0.96). Although harvest date cultivar interactions were significant for both forms of N, overall patterns of N uptake were similar among cultivars. Nitrogen removal from hydroponic solutions (milligrams per plant) was greatest from days 40 to 60; however, N removal (milligrams per gram of tissue dry weight) was greatest in the first month of development and decreased steadily until day 90. From day 40 to 60, new leaf development ceased while inflorescence buds developed to ≈1.0 cm in diameter. After this time, N uptake decreased rapidly as inflorescences expanded. Correlations between morphological changes and N demand could maximize the efficiency of applied N by matching form and application timing with plant needs.

Free access

Abstract

A shoot-tip necrosis in actively-growing shoot cultures of various species has been observed. Using 3 cultivars of Solatium tuberosum grown on media differing in Ca concentration (0.3, 3.0, and 30 mm Ca), typical necrosis was induced or suppressed. Potatoes at 0.3 mm contained about 0.1% Ca g1 dry weight of shoot and also showed the highest incidence of shoot-tip necrosis, ranging from 48% to 72%, depending on the cultivar. Potatoes grown at 3 or 30 mm Ca contained 0.5% or 3% Ca g−1 dry weight of shoot, respectively, and showed only 0% to 9% necrotic shoots, depending on cultivar. In addition to medium Ca content, Parafilm used as the vessel closure promoted shoot-tip necrosis, but increased levels of Ca in the medium tended to overcome the effect. Although cultivar differences in tissue content of other minerals were apparent, these were not associated with the shoot-tip necrosis problem. We conclude that shoot-tip necrosis is associated with a Ca deficiency in actively-growing shoot cultures.

Open Access