Tissue Response of Young Developing Apple Fruits to Freeze Injury1

Abstract

Abstract Morphological and anatomical development of young fruit were studied in relation to the effects of a late spring freeze. ‘Lodi’ and ‘Duchess’ apples were frozen 16 days after full bloom. Samples were collected for anatomical study on 4 subsequent dates following the freeze. The secondary vascular tissues in the outer cortex were affected, resulting in lesions in those tissues where adjacent parenchyma cells had collapsed. The main vascular strands in the outer cortex were killed, the injury extending from fruit base to apex. Separation of the hypodermis from the outer cortex occurred in the fruit apex where tissues were injured most severely. Also injuries were evident contiguous to the core line. Internal phellogen, phellem, and phelloderm in the parenchyma had formed within 18 days after injury. In some cases, cell proliferation and dedifferentiation of cortical parenchyma was noted 46 days after injury.