Respiratory Activity and Duration of Life of Apples Gathered at Different Stages of Development and Subsequently Maintained at a Constant Temperature

Abstract

In Part I of this series (9) it was shown that the respiratory activity of an apple gathered at "maturity" in the autumn and subsequently kept at a constant temperature was characterized by a rise followed by a fall. This rise in respiratory activity was attributed to a change of state in the protoplasm. It was considered to mark the onset of senescence and was termed the "climacteric. " It is interesting to inquire whether the senescent rise occurs in fruit picked in an immature condition.Outline of the main experiment, 1925 In 1925, Bramley's Seedling apples were taken at intervals during their period of growth from selected trees in an orchard near Cambridge. They were immediately brought into the laboratory and placed in glass containers lheld at a constant temperature of 12°C. and ventilated by a constant stream of C02-free air of constant humidity. Under these conditions the rate of CO2 production was followed for as long a period as the fruit remained sound; i.e., free from the attack of fungi. The details of the various gatherings are given in table I. The temperatures in the orchard are given in table II.The glass containers used in these experiments were approximately 700 ml. in volume and were originally designed to hold one fully grown apple. Single apples were the experimental units in the case of the later gatherings. In the case of the earlier gatherings the experimental units consisted of more than one apple (table I). They were ventilated at a rate of about 4 lilers an hour, the incoming CO2-free air being passed through soda lime and through a wash bottle containing a 7 per cent. solution of sodium hydroxide. The number of fruits per container was so arranged that the rate of evolu-1 This is the second of a series of papers on the general subject of "Physiology of PLANT PHYSIOLOGY tion of carbon dioxide per container should be as far as possible the same in all experiments, and in any case not more than 1.5 ml. per hour.The measurement of carbon dioxide was made by the Pettenkofer tube absorption method, using N/10 barium hydroxide as the absorbent. Subsidiary to the main plan of the research, as stated above, a number of additional experiments of an exploratory nature were conducted. The whole apparatus was ilnstalled in a constant-temperature room at 120 C.In operation the carbon dioxide produced by the apples is absorbed by the sodium hydroxide; the oxygen consumed by the apples causes a fall in pressure. Oxygen is then passed in from the graduated burette until the manometer shows that the pressures in the two chambers are again balanced. In starting an experiment the first reading is taken after putting in the apple and allowing an hour to elapse before closing the taps connecting both the apple chamber and balance chamber to air. The barometric reading is taken at this time and the volume reading on the oxygen burette, with the manometer connecting the balance chamber and the apple chamber at zero. The tap connecting the oxygen burette and apple chamber is then closed. Every ten hours...

Molecular Requirements for the Biological Activity of Ethylene

“…CO,, is highly effective in reversing the inhibition of elongation caused by 5 um IAA, and becomes progressively less effective at higher auxin levels because it cannot counteract the action of more than a ppm ethvlene (fig 1), the ethylene content of the tissue at 50 JuM IAA (4). Similarly, CO2 reinstates aulxin inhibited growth in pea roots (7), and it has been demonstrated that auxin inhibits growth in this tisstue by inducing ethylene formation (7) (24) proposed that 0., depletion might interfere with the production and action of ethylene. This suiggestion is stupported by the observation that fruiits evolve less ethylelne (6) 4 and(i 7 show I/Vn3 to be independent of (S) so that the behavior of the tis.sue at all inifinite concenitrationi of ethylene (1/A -0) caln be l)redicted by the low-er dashed line.…”

“…The ability to form complexes with metals is a property of unsatutrated aliphatic compoutnds which is lacking in other aliphatic and all but a few aromatic molecules. The bonding in the complex is influienced by the availabilitv of electrons in the filled r-orbitals of the unsaturated compound, and also by the ease of overlap of these orbitals with those of the metal as determined by (24) proposed that CO., interferes wvith the action of ethylene. At the molecular level stuch an interactioni is not difficult to envision becauise CO, is a close structtural analogule of allene, a compound which substitutes for ethylene in hoth the pea growth aIndI fruiit ripening assays: O -C = O HC = C = CHI, HC --H., carbon dioxide alleine ethylene Since CO, possesses the essential strletuiral featuires needed for ethylene action, except that it lacks the terminal carbon atom ailel is negatively charged on 1)oth ends, might it not act as a competitive inhibitor of ethylene actioni?…”

Ethylene, Seed Germination, and Epinasty

“…The number of reports of ethylene production in the plant kingdom (5,11,13,14) and its association with other plant hormones (7,13) …”

Ethylene: Response of Fruit Dehiscence to CO2 and Reduced Pressure

“…CO2 interferes with responses of plant tissues to ethylene (8); leaf abscission is one response so affected (1). More recently, storage of fruits at reduced atmospheric pressure was shown to delay fruit ripening, apparently by hastening escape of endogenous ethylene (3)(4)(5).…”