Plant Growth Regulation

, Volume 35, Issue 1, pp 1–9 | Cite as

Effects of fruit thinning agents on apple tree canopy photosynthesis and dark respiration

  • Ralf Untiedt
  • Michael Blanke


Effects on photosynthesis of the fruit thinning agents naphthaleneaceticacid (NAA) and three commercial plant growth regulator formulations,naphthaleneacetic acid ('Rhodofix') and naphthaleneacetamide('Amidthin') and 2-chloroethylphosphonic acid('Ethrel')were evaluated with respect to the stress they impose on the fruit tree, usingthe alternate-bearing sensitive apple cv. 'Elstar'. This work wasbased on the hypothesis that plant stress in the form of large reductions inleaf photosynthesis are a pre-requisite for successful fruit thinning. A newtechnology was employed for continuous recording of tree canopyphotosynthesis, dark respiration and carbon balance of apple trees. This wasbased on six canopy chambers, which enclosed apple trees under naturalconditions in the field, with on-line measurements and continuous analysis ofCO2 exchange and automated data acquisition. All employed thinningagents reduced whole tree canopy photosynthesis consistently by3–34% on the five days following their application, withphotosynthesis still declining thereafter in the case of the NAA and'Amid-thin' application. The reduction after application of either'Rhodofix' or 'Ethrel', declined within five days, suchthat most of the original photosynthetic potential was restored, indicatingacceptable phytotoxicity of these three plant growth regulators at theconcentrations used. The effects on dark respiration differed markedly. NAA and'Ethrel' increased dark respirationover-proportionally by up to 106%, whereas 'Amid-thin' and'Rhodofix' decreased it by up to 46%inthe first night after application, thereby drastically affecting the carbonbalance of the tree in opposite ways. These results are integrated into ahypothesis linking basipetal auxin transport, phloem loading, translocation anddeficiency of photoassimilates.

Apple Fruit thinning Malus domestica Borkh. Photosynthesis Phytotoxicity Plant growth regulators Plant stress Respiration Source-sink relationship 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bangerth F. 2000. Abscission and thinning of young fruit and their regulation by plant hormones and bioregulators. Plant Growth Regulation 31: 43–59.Google Scholar
  2. Bangerth F. and Quinlan J. 2000. Editorial preface. Plant Growth Regulation 31: 0–1.Google Scholar
  3. Bertschinger L., Stadler W., Krebs C. and Pfammater W. 1999. Erhöhung der Wirkungssicherheit von Ausdünnungsmitteln: Erfahrungen mit Ethephon und angepaßter Applikationstechnik. Schweiz. Zeitschrift Obst-Weinbau 24: 580–583.Google Scholar
  4. Brown K.M. 1997. Ethylene and abscission. Physiol. Plant. 100: 567–576.Google Scholar
  5. Dennis F.G. 2000. The history of fruit thinning. Plant Growth Regulation 31: 1–6.Google Scholar
  6. Evans M.L. 1984. Functions of hormones at the cellular level of organisation. In: Scott T.K. (ed.), In Hormonal Regulation of Development II. Encyclopedia of Plant Physiology. Vol. 10. Springer Verlag, Berlin, pp. 23–62.Google Scholar
  7. Grochowska M.J. and Lubinska A. 1973. Comparative studies on physiological and morphological features of bearing and nonbearing spurs of the apple tree. II. The effect of fruiting and growth regulator sprays on respiration rate of leaves. Physiol. Plant. 29: 425–429.Google Scholar
  8. Hewitt E.J. 1966. Sand and water cultivation methods. 2nd edn. CAB Farnham Royal, England.Google Scholar
  9. Leopold A.C. 1958. Auxin uses in the control of flowering and fruiting. Ann. Rev. Plant. Physiol. 8: 281–310.Google Scholar
  10. Luckwill L.C. 1953. Studies of fruit development in relation to plant hormones. II. The effect of naphtalene acetic acid (NAA) on fruit set and fruit development in apples. J. Hort. Sci. 28: 25–40.Google Scholar
  11. Moore T.C. 1984. Auxins. In: Moore T.C. (ed.), Biochemistry and Physiology of Plant Hormones. 2nd edn. Springer Verlag, New York, pp. 28–93.Google Scholar
  12. Patrick J.W. 1987. Are hormones involved in assimilate transport?. In: Hoad G.V., Lenton J.R., Jackson M.B. and Atkin R.K. (eds), Hormone action in plant development-a critical appraisal. Long Ashton Symposium Series. Butterworths, London, pp. 175–186.Google Scholar
  13. Schneider G.W. 1978. Abscission mechanism studies with apple fruitlets. Amer. J. Hort. Sci. 103: 455–458.Google Scholar
  14. Schönherr J., Bauer P. and Uhlig B. 2000. Rates of cuticular penetration of 1-naphtylacetic acid (NAA) as affected by adjuvants, temperature, humidity and water quality. Plant Growth Regulation 31: 61–74.Google Scholar
  15. Schumacher R., Neuweiler R. and Stadler W. 1993. Einfluß der Fruchtausdünnung auf Fruchtansatz, Frucht-und Triebwachstum. Schweiz. Zeitschr. Obst-und Weinbau 129: 421–426.Google Scholar
  16. Solomos T. and Laties G. 1976. Effects of cyanide and ethylene on the respiration of cyanide-sensitive and cyanide-resistant plant tissues. Plant Physiology 59: 47–50.Google Scholar
  17. Smith A.R. and Hall M.A. 1993. Mechanisms of ethylene action. Plant Growth Regulation 2: 151–165.Google Scholar
  18. Stopar M., Black B.L. and Bukovac M.J. 1997. The effect of NAA and BA on carbon dioxide assimilation by shoot leaves of spurtype 'Delicious' and 'Empire' apple trees. J. Amer. Soc. Hort. Sci. 122: 837–840.Google Scholar
  19. von Willert D.J., Mayseck R. and Herrpic W. 1995. Experimentelle Pflanzenökologie. 1st edn. Gustav Thieme Verlag, Stuttgart.Google Scholar
  20. Wibbe M.L. and Blanke M.M. 1996. Effects of defruiting on source-sink relationship, carbon budget, leaf carbohydrate and water use efficiency of apple trees. Physiologia Plant. 94: 529–533.Google Scholar
  21. Wibbe M.L. and Blanke M.M. 1997. Effect of fruiting and drought or flooding on carbon dioxide balance of apple trees. Photosynthetica 33: 269–275.Google Scholar

Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • Ralf Untiedt
    • 1
  • Michael Blanke
    • 1
  1. 1.Institut für Obstbau und GemüsebauUniversität BonnBonnGermany

Personalised recommendations