RESPIRATION RATE IN PLANTS
275
ticipates that salt accumulation will be inhibited by heavy metal poisons
such as cyanide, since interference with the respiratory chain will perforce interfere with the concomitant phosphorylation. It also allows for a
selective interference with the accumulating process without interference with the respiratory process, since phosphorylation may be abolished while respiration proceeds unabated.
Some emphasis has been given to the ratio of anions absorbed to 0 2
consumed, and it has been pointed out that the maximal ratio theoretically expected from Lundegardh's hypothesis would be 4. That is, for
each molecule of oxygen consumed, 4 electrons must be passed through
the respiratory chain and hence 4 anions must be accumulated. Robertson and Wilkins (1948) have in fact observed ratios approaching 4 in
experiments with carrot disks. However, since values in excess of 4
(Leaf and Renshaw, 1956), and even as high as 18 (Handley and Overstreet, 1955) have been observed, the redox pump, for this reason and
for those previously mentioned, appears untenable as an explanation
for the mechanism of salt absorption in plants.
With respect to the relationship between salt accumulation and protein
synthesis observed in potato disks by Steward and Preston (1941; see
also Steward and Millar, 1954), at least two interpretations are possible.
The simplest view is that a common underlying change takes place in
the surface cells of aerated potato disks which permits both protein synthesis and salt accumulation. As suggested in a previous section, this
change could be the onset of vigorous oxidative phosphorylation. Alternatively, as suggested by Steward and Street (1947), some energy-rich
phosphorylated nitrogen compound may act as as the carrier for ions,
and release both phosphate and the transported ion within the cell,
where the compound itself participates in protein synthesis. Both views
depend upon the phosphorylative process. Perhaps in the future the use
of selected amino acid analogues or certain antibiotics which interfere
with protein synthesis (see Woolley, 1952) may permit an unequivocal
answer to the question of whether protein synthesis is indispensable for
salt accumulation.
IV. THE CLIMACTERIC
During the development of a variety of fruits, the maturation stage
is followed by a relatively brief period, the climacteric, in which a striking increase in the rate of respiration takes place. The climacteric, to
quote Biale (1950), "marks a transition phase between development
and the onset of functional breakdown, between ontogeny and senescence." Depending upon the fruit involved, it may occur previous to,
or concomitant with, the actual ripening period.
275
ticipates that salt accumulation will be inhibited by heavy metal poisons
such as cyanide, since interference with the respiratory chain will perforce interfere with the concomitant phosphorylation. It also allows for a
selective interference with the accumulating process without interference with the respiratory process, since phosphorylation may be abolished while respiration proceeds unabated.
Some emphasis has been given to the ratio of anions absorbed to 0 2
consumed, and it has been pointed out that the maximal ratio theoretically expected from Lundegardh's hypothesis would be 4. That is, for
each molecule of oxygen consumed, 4 electrons must be passed through
the respiratory chain and hence 4 anions must be accumulated. Robertson and Wilkins (1948) have in fact observed ratios approaching 4 in
experiments with carrot disks. However, since values in excess of 4
(Leaf and Renshaw, 1956), and even as high as 18 (Handley and Overstreet, 1955) have been observed, the redox pump, for this reason and
for those previously mentioned, appears untenable as an explanation
for the mechanism of salt absorption in plants.
With respect to the relationship between salt accumulation and protein
synthesis observed in potato disks by Steward and Preston (1941; see
also Steward and Millar, 1954), at least two interpretations are possible.
The simplest view is that a common underlying change takes place in
the surface cells of aerated potato disks which permits both protein synthesis and salt accumulation. As suggested in a previous section, this
change could be the onset of vigorous oxidative phosphorylation. Alternatively, as suggested by Steward and Street (1947), some energy-rich
phosphorylated nitrogen compound may act as as the carrier for ions,
and release both phosphate and the transported ion within the cell,
where the compound itself participates in protein synthesis. Both views
depend upon the phosphorylative process. Perhaps in the future the use
of selected amino acid analogues or certain antibiotics which interfere
with protein synthesis (see Woolley, 1952) may permit an unequivocal
answer to the question of whether protein synthesis is indispensable for
salt accumulation.
IV. THE CLIMACTERIC
During the development of a variety of fruits, the maturation stage
is followed by a relatively brief period, the climacteric, in which a striking increase in the rate of respiration takes place. The climacteric, to
quote Biale (1950), "marks a transition phase between development
and the onset of functional breakdown, between ontogeny and senescence." Depending upon the fruit involved, it may occur previous to,
or concomitant with, the actual ripening period.