276
GEORGE G. LATIES
A heterogeneous group of fruits, including the apple, pear, avocado,
and banana, exhibit a climacteric (Kidd and West, 1945; Biale et al,
1954). The causes underlying the climacteric in apple (Hulme, 1954;
Pearson and Robertson, 1954) and in avocado (Millerd et al, 1953;
Romani and Biale, 1957) have recently been investigated and suggestions
as to their nature have been offered.
1. The Climacteric in Apples
Kidd and West (1945) have noted the relatively constant rate of respiration exhibited by apples throughout the period of cell enlargement
when the rate is expressed on a unit nitrogen basis. An autoregulatory
mechanism which controls the concentration of some unspecified substrate was offered as an explanation of the observed constancy, although
Kidd and West clearly recognized that a variety of cellular components
which could reasonably be considered as respiratory metabolites (glucose, fructose, starch, sucrose, malic acid) varied in concentration independently of the respiration rate.
In an effort to avoid this obvious inconsistency, and at the same time
to explain the sudden departure from constancy represented by the climacteric, Pearson and Robertson (1954) have recently examined the
thesis, proffered by Maskell (see Pearson and Robertson, 1954), that the
rate of respiration in the apple is controlled by the effective concentration of phosphate acceptor, which in turn is related both to its own absolute concentration and rate of turnover (see Hulme, 1954).
From approximately 60 days after full blossom until well beyond the
onset of the climacteric (190 days from full blossom), the respiration of
slices prepared from freshly picked apples was found to be limited by
the level of endogenous phosphate acceptor. That is to say, the respiratory rate was increased by additions of dinitrophenol. The stimulation of
the respiration by dinitrophenol increased percentagewise through 150
days, and remained contant for 40 thereafter. With the development of
the climacteric, the rate of respiration of untreated disks rose sharply,
and, since the maximal rate induced by dinitrophenol remained unchanged, the percentage stimulation evoked by dinitrophenol rapidly
decreased. The respiration of disks from preclimacteric apples was found
to respond to ATP as well as to dinitrophenol. The highest percentage
increase in respiration elicited by ATP was approximately 40%, as compared with a 75% stimulation evoked by dinitrophenol.
The respiration rate of either whole apples or apple disks drops
sharply during the first 150 days from full blossom when expressed on a
unit fresh weight basis, for although the protein content and total respiration increase during the first 120 days, the increase is proportional to
GEORGE G. LATIES
A heterogeneous group of fruits, including the apple, pear, avocado,
and banana, exhibit a climacteric (Kidd and West, 1945; Biale et al,
1954). The causes underlying the climacteric in apple (Hulme, 1954;
Pearson and Robertson, 1954) and in avocado (Millerd et al, 1953;
Romani and Biale, 1957) have recently been investigated and suggestions
as to their nature have been offered.
1. The Climacteric in Apples
Kidd and West (1945) have noted the relatively constant rate of respiration exhibited by apples throughout the period of cell enlargement
when the rate is expressed on a unit nitrogen basis. An autoregulatory
mechanism which controls the concentration of some unspecified substrate was offered as an explanation of the observed constancy, although
Kidd and West clearly recognized that a variety of cellular components
which could reasonably be considered as respiratory metabolites (glucose, fructose, starch, sucrose, malic acid) varied in concentration independently of the respiration rate.
In an effort to avoid this obvious inconsistency, and at the same time
to explain the sudden departure from constancy represented by the climacteric, Pearson and Robertson (1954) have recently examined the
thesis, proffered by Maskell (see Pearson and Robertson, 1954), that the
rate of respiration in the apple is controlled by the effective concentration of phosphate acceptor, which in turn is related both to its own absolute concentration and rate of turnover (see Hulme, 1954).
From approximately 60 days after full blossom until well beyond the
onset of the climacteric (190 days from full blossom), the respiration of
slices prepared from freshly picked apples was found to be limited by
the level of endogenous phosphate acceptor. That is to say, the respiratory rate was increased by additions of dinitrophenol. The stimulation of
the respiration by dinitrophenol increased percentagewise through 150
days, and remained contant for 40 thereafter. With the development of
the climacteric, the rate of respiration of untreated disks rose sharply,
and, since the maximal rate induced by dinitrophenol remained unchanged, the percentage stimulation evoked by dinitrophenol rapidly
decreased. The respiration of disks from preclimacteric apples was found
to respond to ATP as well as to dinitrophenol. The highest percentage
increase in respiration elicited by ATP was approximately 40%, as compared with a 75% stimulation evoked by dinitrophenol.
The respiration rate of either whole apples or apple disks drops
sharply during the first 150 days from full blossom when expressed on a
unit fresh weight basis, for although the protein content and total respiration increase during the first 120 days, the increase is proportional to