Shoot tips of Seckel pear and Almey crabapple were cultured on liquid MS medium containing 8.8#M BA. Changes in shoot proliferation and growth and in nutrient and carbohydrate composition of the medium were determined during a 9 week culture period. Whereas shoot proliferation in crabapple increased linearly during the culture period, it levelled off after week 4 in pear. Explant dry weight in both genera showed a linear increase over time. Culture medium pH decreased in the initial weeks and increased thereafter. There was a rapid decline in medium P and Fe concentration with both genera and of Zn in the medium of crabapple. In no instance did the rate of depletion of any nutrient from the medium of pear cultures exceed that measured in the crabapple medium. The decline in sucrose concentration in the medium was similar for both genera and was accompanied by an increase in the level of glucose and fructose. At the end of the culture period slightly over half of the initial carbohydrate level remained in the medium.

Shoot-tip cultures of Quince C (Cydonia oblonga Mill.) initiated on Murashige & Skoog (MS) medium containing 5 #M BA and 0.6% Phytagar showed both shoot-tip necrosis and severe vitrification. Culturing explants on medium containing 1.2% Phytagar and Ca levels of 3 mM (MS medium), 18 mM and 30mM showed a decrease in growth with increasing medium Ca levels, being especially severe at 30 mM. The Ca content of the explants increased linearly with increasing medium Ca. Culturing explants on medium containing 3 mM, 9 mM, and 18 mM Ca at 0.6, 0.9, and 1.2% agar resulted in reduction in growth, shoot-tip necrosis, and vitrification when either factor was increased. The reduction in shoot-tip necrosis could be accounted for primarily by an increase in medium Ca levels but may also be affected by a change in explant growth. Increasing Ca concentration in the medium resulted in a linear increase in explant K, Ca, Mg, and B levels and a decrease in Mn and Na. Although increasing medium Ca or agar levels reduced vitrification, it is unclear whether they were the direct cause of the reduction in vitrification or whether this response was an effect of the reduction in culture fresh weight.

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Natural and 10B-enriched boric acid solutions were sprayed on whole trees or certain parts of `Reliance' peach trees (Prunus persica L. Batsch) to estimate the uptake and translocation of B. The tissues were analyzed for total B and 10B: 11B ratio. The single or multiple spray treatments of 233 mg B/liter applied at full bloom (FB), FB + 2 weeks, and FB = 4 weeks did not increase B concentrations in leaves or stems collected 45,75, and 105 days following FB. Individual limbs sprayed with 0,200,400,600, or 1200 mg B/liter did not affect B concentrations in six aerial plant parts harvested 3 days following treatment. Boron uptake and translocation were also studied by applying 30 μl of 600 mg B/liter from 10B-enriched boric acid as spot treatments to various peach plant parts. Leaves, stems, and fruit absorbed 10B and translocated it to nontreated tissues. However, only a small amount of 10B was absorbed by 3 days after treatment.