STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES

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1 New Phytl. (968) 67, STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES III. THE MECHANISM OF THE 'CLIMACTERIC RISE IN RESPIRATION IN APPLES BY J. BARKER Btany Sclil, Liiiversitv f Cambridge {Received June 967) The cntents f glucsc-6-phsphate, fructse diphsphate, 3-phsphglycerate and phsphenlpyruvate were substantially unchanged during the 'climacteric' rise in CO^ utput in apples. The mechanism f the 'climacteric' increase in respiratin in apples thus appears t differ frm that in bananas. INTRODUCTION During the past 4 years varius theries have been advanced t explain the large rise in rate f respiratin, that is, the 'climacteric' rise, w hich accmpanies ripening in certain fruits, but n bypthesis has been accepted as prved (Blackman and Parija, 928; Kidd and West, 93; Millerd, Bnner and Biale, 953 ; Pearsn and Rbertsn, 954; Hulme, 954; Neale and Hulme, 9^8; Lieberman and Biale, 956; Rwan, McGlassn and Pratt, 96; Rwan, 966; Hulme, Jnes and Wltrtn, 963). In earlier wrk with bananas the increase in CO2 utput during the 'climacteric' was shwn t be accmpanied by a large increase in the cntent f fructse diphsphate (FDP) and a substantial initial decrease f phsphenlpyruvate (PEP) (Barker and Slms, 962; Slms, 963). The aim f the present wrk was t ascertain whether similar changes in these phsphate cmpunds ccurred during the 'climacteric' in apples. METHODS At each gathering sme twenty-fur Bramley's Seedling apples* were picked frm a selected tree and were placed at 2" C, each in a separate cntainer, thrugh which was passed a current f CO^-free air at a rate f abut 2.5 I/hur. Each apple was eventually analysed separately fr phsphate esters. The prcesses f killing, extractin and estimatin are described elsewhere (Barker et al.., 964). The mean recveries f glucse-6-phsphate (G6P), f FDP, f 3-phsphglycerate (3-PGA) and f PEP added t the extract were respectively 8, 89, 95 and 97%. N crrectins fr lsses f phsphate cmpunds in the extract have been made. RESULTS Experiment i. First gathering, picked 23 July 962; mean weight 78^ (Fig. i) CO2 utput (Fig. ia). Each crss in Fig. ia represents the CO, utput at the time f * I am grateful t Mr Franklin f Cttenham frm whse rchard the apples were gathered. 23

2 24 J. BARKER analysis f a 'pre-climactcric' apple. The initial rate f CO, utput f the apples immediately after picking was high and, apart frm the 'climacteric' rise, the rate decreased cntinuusly at 2" C. After varius times at 2' C the CO2 utput increased markedly in the 'climacteric' rise. Each apple shwing the rise was taken fr analysis at what 4 - (a ) CO _ 8 - \ (b)g6p 4 - ' / -2 - (c) FDP - - c) Ox 2- - f (d) 3-PG/: - - ^ x - _ (e)pep ' O x - nil Days Fig. I. Experiment i. Changes in (a) rate f CO2 utput and (b-e) cntents f phsphate cmpunds, (b) Glucse-6-phsphate (G6P); (c) fructse diphsphate (FDP); (d) 3- phsphglycerate (3-PG.-\) and (e) phsphenlpyruvate (PFP). Pre-climacteric apples, and x ; climacteric apples, :. In this and JFig. 2 the date f picking is shwn as days; in all figures the rate f CO2 utput is expressed as mg/i g fresh weight/hur and the cntents f phsphate cmpunds as //mles/ g fresh weight. appeared t be the peak f the 'climacteric', the CO, utputs at the peak fr the different apples being shwn as circles in Fig. ia. Phsphate cmpunds (Figs. ib-e). The cntent f G6P was high immediately after picking and decreased fr sme 3-4 days at 2 C. The fur values btained fr the G6P cntent f 'climacteric' apples are similar t tbe 'pre-climacteric' amunts.

3 Mechanism f 'climacteric' rise in apples 25 The cntents f FDP f the 'pre-climacteric' and 'climacteric' apples were very variable hut there was n indicatin that the amunt f this ester increased markedly in the 'climacteric' as ccurred in hananas (Barker and Slms, 962; Slms, 963); in hananas the FDP increased by sme twenty-five-fld during the 'climacteric'. Fr apples the cntents f 3-PGA and f PEP were als highly variable but again there was n sign f the large decrease in PEP in the 'climacteric' such as ccurred in bananas (Slms, Experiment 2. Secnd gathering picked 29 August 962; mean weight 3 g (Fig. 2) CO2 utput (Fig. 2a). The CO, utput f the 'pre-climacteric' apples was nt as high initially at 2 C as fr Experiment i but again decreased in strage. The circles in Fig. 2a again represent the CO, utput at the peak f the 'climacteric' )- -- (d) 3-PGA I r -T " ~ O,^ r. I (a)co^ (b) G6P FOP J H -5 (e) PEP ^,, _ IIIII Days Fig. 2. Experiment i. Changes in (a) rate f CO2 utput and (b-e) cntents f phsphate cmpunds, (b) Glucse-6-phsphate (G6P); (c) fructse diphsphate (FDP); (d) 3-phsphglycerate (3-PGA); and (e) phsphenlpyruvate (PFP). Pre-climacteric apples, x x and ; climacteric apples, O. Phsphate cmpunds (Figs. 2h-e). The cntent f G6P f pre-climacteric apples was nce mre high initially at 2"" C thugh lwer than fr Experiment i; the value again decreased initially at 2"" C. The amunts f G6P f 'climacteric' apples were nce mre similar t thse f the 'pre-climacteric' fruits. The cntents f FDP, 3-PGA and PEP f 'climacteric' apples did nt differ substantially frm thse f the 'pre-climacteric' fruits. DISCUSSION During the 'climacteric' rise f CO2 utput in bananas the cntent f FDP increased by sme twenty-fld, while that f PEP decreased initially by sme 8",, (Barker and Slms, 962; Slms, 963). The mst prbable cause f the rise in CO, utput in bananas

4 2l6 J. BARKER was thut;;lit t be a taster rate t metablism f PEP, which prduced extra adensine triphsphate (.V'TP) in the vicinity f the sugar phsphrylating and glyclytic enzymes (Slms, K/3), the extra ATP was thught t increase the cntent f P'DP, the rise f the latter substrate accelerating the rate f CO2 utput. In ur data tr apples there was n indicatin f any substantial increase in FDP r decrease in PEP during the 'chmacteric' rise in CO, utput and the mechanism f the 'chmacteric' in apples thus appeared t differ frm that in bananas. Rwan, Pratt and Rbertsn (iqys) have already suggested that the mechanism t the 'chmacteric' may vary in different fruits. Mrever, there is evidence that the 'climacteric' in apples is in part at least due t metablism f the reserves f malic acid (Hulme et al., 963, 965; Jnes, Huhne and Wltrtn, 965). But this explanatin f the mechanism f the 'climacteric' in apples des nt appear t be valid fr bananas since in this fruit the respiratry qutient remained at abut i. thrughut the 'climacteric' rise in COj utput. As mentined abve, the rate f CO, utput and the G6P cntent decreased tgether initially at 2 C in bth experiments and these tw functins were lwer at the time f picking fr Experiment 2 than fr Experiment i (Figs, i and 2). The crrelatin between rate t CO, utput and cntent f G6P is shwn in Fig. 3; further wrk is needed t determine \\ hether r nt the relatin is due t G6P acting as a respirable substrate Cntent f G6P Fig. 3. Relatin between rate f COj utput and cntent f glucse-6-phsphate (G6P) bth immediately after picking and during sjurn at 2" C. Experiment, ii; Experiment 2,. ACKNOWLEDGMENTS This wrk was cnducted partly with the aid f a grant fr a special research awarded by the Department f Scientific and Industrial Research (nw Science Research Cuncil). This assistance is gratefully acknwledged, as is als the interest and encuragement f the Agricultural Research Cuncil. I am grateful t Dr F. A. Isherwd fr advice and t Mr M. Askham, Mr P. Curtis, Mr R. Jakes and Mr B. Rystn fr their assistance.

$A., JAKES, R., SOLOMOS, T. & YOUNIS, I\I. F. (964). Studies in the respiratry and carbhydrate metabhsm f plant tissues. l\'. The determinatin f certain phsph;ite cmpunds in plant extracts, jf. cxp.$

5 Mechanism f 'climacteric' rise in apples 27 REFERENCES BARKER, J. & SOLO.MOS, T. (962). Mechanism f the 'climacteric' rise in respiratin m b.mana fruits. Nature, Ltid., 96, 89. BARKER, J., ISHERWOOD, F. A., JAKES, R., SOLOMOS, T. & YOUNIS, I\I. F. (964). Studies in the respiratry and carbhydrate metabhsm f plant tissues. l\'. The determinatin f certain phsph;ite cmpunds in plant extracts, jf. cxp. Bt., 5, 284. BLACKMAN, F.. & PARIGA, P. (928)..Analytic studies in plant respiratin. I. The respiratin f a ppulatin f senescent ripening apples. Pr<jc. R. Sue. Ii, 3, 42. HlLME, A. C. (954). Studies in the nitrgen metablism f apple fruits. The climacteric rise in respiratin in relatin t changes in the equilibrium f prtein synthesis and breakdwn. J. e.\p. Bat., 5, i 5. HlLME,.. C, JONES, J. D. & WUOLIORION, L. S. C. (i96-t). The respiratin climacteric in apples. Pic. R. Sc, B, 58, 54. HuLME, A. C, JONES, J. D. & W'OOLTORTON, L. S. C. (965). The respiratin climacteric in apple fruits. Bichemical changes ccurring during the develpment t the climacteric in fruit n the tree. Nezv Phytl., 64, 52. JONES, J. D., HULME, A. C. & WOOLrORION, L. S. C. (965). The respiratin climacteric in apple fruits. Bichemical changes ccurring during the develpment f the climacteric in fruit detached frm the tree. Neu' Phytl., 64, 58. KiDD, F. & WEST, C. (93). Physilgy f fruit. I. Changes in the respiratr)- actixity f apples during their senescence at different temperatures. Prc. R. Sc, B, 6, 93. LlEBERNL\N, M. & BL\LE, J. B. (956). Cfactr requirements fr xidatin f alpha-ket acids by sweet ptat mitchndria. PI. PhysiL, Lancaster, 3, 425. MlLLERD, A., BNNER, J. & BL^LE, J. B. (i953). The climacteric rise in fruit respiratin as cntrlled by phsphrylative cupling. PI. PhysiL, Lancaster, 28, 52. NEALE, G. A. & HULME,.A. C. (958). The rganic acid metablism f Bramley's.Seedling apple peel. y. exp. Bt., 9, 42. PEARSON, J. A. & ROBERTSON, R. N. (954). The physilgy f grwth in apple fruits. \'I. The cntrl f respiratin rate and synthesis. Aust.jf. bil. Set., 7, i. ROWAN, K. S. (966). Phsphrus metablism in plants. Int. Rev. Cytl., 9, 3. ROWAN, K. S., PRATT, H. K. & ROBERTSON, R. N. (958). The relatinship f high-energy phsphate cntent, prtein synthesis and the climacteric rise in the respiratin f ripening avcad and tmat fruits. Aiist. J. bil. Set.,, 329. ROWAN, K. S., MCGLASSON, W. B. & PRATT, H. K. (96). Respiratin f ripening cantalupe fruit and accepted level. Fedn Pre. Fedn Am. Ses exp. Bil., 2, 374. SOLOMOS, T. (963). Studies f resptratry metablism f bananas. Ph.D. thesis. University f Cambridge.

STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES

New Phytl. (968) 67, 49553. STUDIES IN THE RESPIRATORY AND CARBOHYDRATE METABOLISM OF PLANT TISSUES V. CHANGES IN RATE OF CO^ OUTPUT AND IN CONTENT OF VARIOUS PHOSPHATE COMPOUNDS IN POTATOES BY J. BARKER