Differential uptake of B by two tomato genotypes (Lycopersicon esculentum Mill) occurred both in soil and in solution culture. Boron deficiency developed in T3238 tomato grown on seven acid soils but not on five calcareous soils. The acid soils contained less, and the alkaline soils contained more, than 0.20 ppm hot-water-extractable B. T3238 tomato required several times as much hot-water-extractable B in a soil as Rutgers. With adequate B in the growth medium for uptake, T3238 utilized the transported B as well as did Rutgers. T3238 and Rutgers tomatoes can be used as indicator plants to test B availability in soils. Boron deficiency symptoms developed in the apical meristem and in the developing leaf of T3238 tomato within 48 hours after the plants were transferred from solutions containing 0.52 mg/liter of B to those containing 0.07 mg/liter. Boron deficiency in apical meristematic tissue caused: (i) increase in cell size; (ii) nuclear enlargement; and (iii) tissue disintegration. In leaf tissue B deficiency caused: (i) necrosis and collapse of the upper epidermal and palisade cells; and (ii) accumulation of phenolic materials in these areas. Rutgers developed no deficiency symptoms under the same conditions.

Cuts were made in the surface of the shoot apices of Euphorbia lathyris, tomato (Lycopersicon esculentum), and Pea (Pisum sativum) while they were completely immersed in water or aqueous mannitol at various concentrations, or in near-saturated air. Gaping occurred all over the apical dome of Euphorbia and on the tomato apex at the site of emergence of the primordial bulge. Maximum gaping occurred in near-saturated air and under water, and was progressively reduced with increasing osmotica. It is concluded that the gaping results from tension in the surface cells and is not caused by superficial drying out. No gaping occurred in the axil of the newly formed primordium of the tomato nor anywhere in the apex of the pea. Histological evidence suggests that these tissues are under lateral compression. The mechanical stresses involved are discussed in relation to the morphology of the apices together with existing data on the distribution of cell division during primordia formation.