Changes in the cotyledons of Cucurbita maxima during germination. V. The nuclear envelope

Abstract

The frequency and distribution of nuclear pores in cotyledon mesophyll cells of Cucurbita maxima were studied from early stages of germination until cotyledon senescence. Changes in nuclear volumes and nuclear surface areas were also studied. The number of nuclear pores per square micron of nuclear surface area increased significantly when the cotyledon changed from a storage organ to a photosynthetic leaf and then decreased with the onset of senescence. Temperature of seedling growth influenced the number of nuclear pores per square micron of nuclear envelope. Plants grown under different temperatures to about the same morphological stage of development had significantly different numbers of nuclear pores per square micron of nuclear envelope. Plants grown under cooler temperatures had more nuclear pores per unit area than did plants grown under warmer conditions, even where nuclear surface areas were not significantly different between plants grown at the two different temperatures.