The phloem mobility of boron (B) in plants varies dramatically among species. Variations in phloem B mobility occur as a consequence of the presence of sugar alcohols (polyols) in some species but not in others, and these differences in phloem B mobility profoundly affect the expression of B toxicity symptoms. Twenty-four species including common ornamental species varying in sugar alcohol content, were selected to test their response to B toxicity. Species that do not produce sugar alcohols exhibited previously described B toxicity symptoms that include accumulation of high concentrations of B in, and burning of, the tip and margin of old leaves. In the sugar-alcohol-producing species these symptoms were absent, and B toxicity was expressed as meristematic dieback and an accumulation of B in apical tissues. These symptoms have not previously been associated with B toxicity in these species and hence may have been frequently misdiagnosed.
Patrick H. Brown, Hening Hu and Warren G. Roberts
Richard H. Ozminkowski Jr., Randolph G. Gardner, Warren R. Henderson and Robert H. Moll
Two inbred lines of fresh-market tomato (Lycopersicon esculentum Mill.), NC 20G-1 and NC 53G-1, both exhibiting prostrate growth habit (PGH), were crossed with the upright growth habit cultivar Piedmont and advanced to the F2 generation. Plants of each F2 population were grown without plant support on black plastic and subjectively rated in field plots for PGH. Extreme upright and prostrate plants were chosen from each F2 population for harvest. Mean comparisons between plants of extreme upright and prostrate habit showed increased total and marketable yields from plants with a prostrate habit. Decay and groundscarring of fruit were less in prostrate than in normally upright plants; the percentage of misshapen fruit was similar in both. The PGH character may be useful in increasing total and marketable yield of ground-culture tomatoes.
Richard H. Ozminkowski Jr., Randolph G. Gardner, Robert H. Moll and Warren R. Henderson
Prostrate growth habit (PGH) in tomato (Lycopersicon esculentum Mill.) lines derived from breeding material developed at the Agriculture Canada Research Station, Beaverlodge, Alberta, was the subject of a quantitative inheritance study. Plants with PGH have an increased lateral branch angle, relative to upright plants, and crown-set fruit supported above the soil surface making hand harvest easier. Genetic parameters were estimated in two families (20G and 53G), each containing PGH and upright-habit parental lines, F1, F2, and backcrosses to each parent. Field-grown plants were subjectively rated twice during the growing season. Broad-sense heritability of PGH in family 20G was estimated to be 0.65 and 0.71 for ratings of plant growth habit 6 and 9 weeks after transplanting, respectively, and 0.71 and 0.68 for those of family 53G. Narrow-sense heritability was estimated to be 0.83 and 1.05 for the two ratings in the 20G family and 0.77 and 0.78 in the 53G family. F1 and F2 means were not different from mid-parent values. The genetic variance was entirely additive and expression was influenced by the environment. The data did not support the hypothesis that PGH was controlled by a single gene.