Grape Physiology

1. Grape Physiology Plant Growth Regulators tcreagh@eit.ac.nz

2. 7.1 Hormones • Plant Growth Regulators are substances synthesized by the plant to act as messengers • They are produced at one site and generally transported in the xylem or phloem to another to induce a physiological reaction (eg growth) tcreagh@eit.ac.nz

3. 7.1 Hormones • Very small amounts of hormone are required to cause an action • They may act either alone or interact with other hormones tcreagh@eit.ac.nz

4. 7.1 Hormones • They may also cause different effects in different parts of the grape vine • These reactions are complex and not always fully understood tcreagh@eit.ac.nz

5. 7.1 Hormones • There are five main groups of hormones in plants tcreagh@eit.ac.nz

6. Auxins tcreagh@eit.ac.nz

7. Auxins Source of production • New vegetative growth • Young leaves • Seeds tcreagh@eit.ac.nz

8. Auxins Actions • Attracts sugar and nutrients to site of production • Stimulates cell growth in young tissue • Inhibits lateral budburst further down the shoot ie apical dominance • Promotes growth towards light tcreagh@eit.ac.nz

9. Gibberellins tcreagh@eit.ac.nz

10. Gibberellins Source of production • Young growing shoot and leaves • Root tips Actions • Suppresses flower bud initiation and fruitfulness in cool weather/poor light • Promotes growth and cell elongation Example • GA-3 is sprayed on seedless grapes to increase grape size and yield tcreagh@eit.ac.nz

11. Cytokinins tcreagh@eit.ac.nz

12. Cytokinins Source of production • Root tips Actions • Promotes cell multiplication in differentiating tissues at apices • Attracts auxin and gibberellin, sugars, nutrients • Promotes even budburst • Promotes lateral branching tcreagh@eit.ac.nz

13. Cytokinins • Promotes development of leaves, fruit structures, fruit set with gibberellins to balance fruitfulness of lateral buds • Delays senescence • Promotes berry as a sink • Involved in anthocyanin and flavour formation tcreagh@eit.ac.nz

14. Abscissic Acid tcreagh@eit.ac.nz

15. Abscissic Acid Source of production • Mature leaves • Seeds, roots tcreagh@eit.ac.nz

16. Abscissic Acid Action • Generally counteracts effects of auxin, gibberellin and cytokinin • Induces stomatal closure in response to water stress • Reduces growth in response to water stress, cold and short days • Possibly promotes ripening as auxin production reduces in seeds tcreagh@eit.ac.nz

17. Ethylene tcreagh@eit.ac.nz

18. Ethylene Source of production • Mature leaves and other parts of vine Action • Affects many types of growth, not all of which are clearly defined • Promotes ripening and berry colour • Promotes abscission zone development tcreagh@eit.ac.nz

19. 7.1 Hormones • In general terms, auxins and gibberillins complement each other, promoting growth • Cytokinin induces fruit and ripening when weather conditions and other factors are suitable for fruit to ripen • Absissic acid and ethylene promotes ripening and prepares the vine for dormancy tcreagh@eit.ac.nz

20. Hormones • Table 7.2: factors affecting hormone production tcreagh@eit.ac.nz

21. Some Practical Implications of Plant Growth Regulators • Auxin is produced in the growing tips and travels downwards • To prevent uneven budburst and end point principle, where the end bud bursts first, canes are arched during pruning to slow the movement of auxin along the cane • Spur pruning is not subject to uneven budburst tcreagh@eit.ac.nz

22. Some Practical Implications of Plant Growth Regulators • Removal of the growing tip will promote lateral growth, as the site of auxin inhibition of budburst is removed tcreagh@eit.ac.nz

23. Some Practical Implications of Plant Growth Regulators • Shaded shoots tend to grow long and spindly with long internodes until they reach light, where growth becomes normal • Buds also tend to be less fruitful in shaded vines, due to the actions of gibberellin tcreagh@eit.ac.nz

24. Some Practical Implications of Plant Growth Regulators • Berry size is related to the number of seeds (developed embryos) due partly to hormone production, increasing the berry as a sink tcreagh@eit.ac.nz

25. Some Practical Implications of Plant Growth Regulators • Warm, well drained soils during budbreak improve the evenness of budburst due in part to cytokinins produced from increased root growth promoted due to the warmer conditions tcreagh@eit.ac.nz

26. Some Practical Implications of Plant Growth Regulators • Fruitfulness • The number of clusters is increased with warmer temperatures due to cytokinin production • Whereas in shaded or cool situations gibberellins tends to promote tendril formation tcreagh@eit.ac.nz

27. Some Practical Implications of Plant Growth Regulators • As vegetative growth slows close to ripening, less auxin and gibberellins are produced • Less auxin is produced as the seed ripens in stage 2 tcreagh@eit.ac.nz

28. Some Practical Implications of Plant Growth Regulators • Abscissic acid increases in proportion inducing véraison and the berry becomes a major sink tcreagh@eit.ac.nz

29. Some Practical Implications of Plant Growth Regulators • Cytokinin also increases, attracting sugar to the berry, abscissic acid and perhaps having an effect on berry colour and flavour • Continuing ripening during cool climates may depend partially on warmer soil temperatures favouring cytokinin production tcreagh@eit.ac.nz

30. Some Practical Implications of Plant Growth Regulators • Ethylene is used as a growth regulator • Ethephon liberates ethylene • Depending on timing of application it may: • Increase berry colour and enhance maturation • Slow vegetative growth • Enhance budbreak • Cause cluster abscission tcreagh@eit.ac.nz

31. Some Practical Implications of Plant Growth Regulators • Researchers have found that irrigating one side of a plant can produce the same crop with half the water • It can also increase colour and flavour production by up to 30% An Example…… tcreagh@eit.ac.nz

32. Some Practical Implications of Plant Growth Regulators • As one half of the vine's root system is watered, the other half begins to dry out • This stimulates the production of abscissic acid • This causes the leaves to partly close their stomata and the shoot growth to uniformly slow down, thereby conserving water tcreagh@eit.ac.nz

33. Some Practical Implications of Plant Growth Regulators • If this situation is maintained, shoot function will eventually recover • However, at about the time that recovery starts the other side of the root system is watered • This leaves the first side to dry out which ensures one side is constantly in a 'dry phase' tcreagh@eit.ac.nz

34. Hormones and Initiation of Inflorescence Primordia

35. Hormones and Initiation of Inflorescence Primordia • Hormones are synthesized within the vine control the initiation and development of inflorescence primordia within the bud • They do not act in isolation • Relative proportions of determine what is formed tcreagh@eit.ac.nz

36. Hormones and Initiation of Inflorescence Primordia • The number size of inflorescences is the first indication of yield tcreagh@eit.ac.nz

37. Yield components tcreagh@eit.ac.nz

38. Definitions • Fecundity • the potential reproductive capacity of an organism or population • Fruitfulness • The presence of inflorescence primordia in latent buds • Mean bunch number per shoot • Three step process: • Formation of an uncommitted primordium • Development into inflorescence primordium • Formation of flowers tcreagh@eit.ac.nz

39. Buds tcreagh@eit.ac.nz

40. Buds • The grapevine buds develop in the axil of the leaf and the shoot, that is, at the node. • There are various types of grapevine buds: • Prompt bud • Compound bud • Latent bud tcreagh@eit.ac.nz

41. tcreagh@eit.ac.nz

42. Lateral or Prompt bud • The lateral shoot arises from the lateral or prompt bud • It is formed between the primary or new season’s shoot and the leaf arising from it, that is, in the leaf axil • It may be also referred to as the true axillary bud tcreagh@eit.ac.nz

43. tcreagh@eit.ac.nz

44. Lateral or Prompt bud • The prompt bud can burst in the current season to produce short shoot known as the lateral • However, lateral shoots will form only under certain conditions • Vigorous vines or if topping occurs early in the season tcreagh@eit.ac.nz

45. Lateral or Prompt bud • Lateral shoots are generally unfruitful but bunches may grow on the lateral shoot • If they do they are usually small and ripen after those carried on the primary shoot • These bunches are referred to as 'second set' tcreagh@eit.ac.nz

46. Compound Buds • The compound bud is formed after the prompt bud and develops more slowly • These buds also develop in the leaf axil at the node. • It consists of three true buds tcreagh@eit.ac.nz

47. tcreagh@eit.ac.nz

48. tcreagh@eit.ac.nz

49. Compound Buds • The compound bud does not burst until the season after its development • Generally only the middle, or primary, bud bursts to develop the primary (main) shoot • If this is damaged (wind, frost, etc) then the secondary or tertiary buds may burst • However, these buds are generally less fruitful, that is they have fewer bunches per shoot tcreagh@eit.ac.nz

50. Compound Buds • The number of potential bunches per bud develops in the previous season before bud burst • Those at the base of the shoot will be more developed than those close to the apical tip. tcreagh@eit.ac.nz