Protein Nitrogen Content and Phosphorylative Activity of Apple Fruits During Ripening and Senescence

Abstract

Respiratory activity, protein nitrogen content and rate of esterification of infiltrated P32 have been followed during ripening and senescence at 20[degree]C in detached fruits of five apple varieties. A peak in protein nitrogen content accompanied the respiratory climacteric, and at least one additional peak occurred during senescence. The senescent increase in protein nitrogen was in most cases much greater than the increase at the climacteric. It is suggested that the diversion of energy to the synthesis of this protein may play a role in hastening the onset of senescent breakdown of the fruit tissue. While no conclusions could be drawn with respect to quantitative changes in phosphorylative activity, the tissue was shown to retain the capacity to esterify added phosphate for as long as the experiment continued, which was up to 4 months after the occurrence of the climacteric. Democrat apple tissue still showed this capacity after the fruit had been stored at 1[degree]C for 12 months.