Anatomical and Physiological Responses of Squash to Various Levels of Boron Supply

Abstract

Squash, Cucurbita maxima, was grown in nutrient solns. with and without B. Material was collected every 2d day for 10 days after the B-deficiency treatment was started. Anatomical examinations and catalase detns. were made on the plant organs. Anatomical responses were evident in stem and root tips, 2d leaves, and stems 2 days after the B-deficiency was established. In the stem tips, cell enlargement and collapse occurred in the region of cell division and in the cortex of the more mature portions. Hypertrophy of the xylem parenchyma and the parenchyma in the regions where the internal and external cambiums usually originate was the first visible response in organs with differentiated vascular bundles. With the exception of root tips, the greatest catalase activity was measured in the organs with the earliest and most extensive histological response, the differences being obvious even on the 2d day of treatment. , B-deficient tissue, in some cases, showed 3 times as much catalase activity as comparable control tissue. External deficiency symptoms were detd.