Grape physiology
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Grape Physiology. P lant Growth Regulators. 7.1Hormones. P lant 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).

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Grape Physiology

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Grape physiology

Grape Physiology

Plant Growth Regulators

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7 1 hormones

7.1Hormones

  • 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)

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7 1 hormones1

7.1Hormones

  • Very small amounts of hormone are required to cause an action

  • They may act either alone or interact with other hormones

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7 1 hormones2

7.1Hormones

  • They may also cause different effects in different parts of the grape vine

  • These reactions are complex and not always fully understood

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7 1 hormones3

7.1Hormones

  • There are five main groups of hormones in plants

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Auxins

Auxins

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Auxins1

Auxins

Source of production

  • New vegetative growth

  • Young leaves

  • Seeds

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Auxins2

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

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Gibberellins

Gibberellins

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Gibberellins1

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

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Cytokinins

Cytokinins

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Cytokinins1

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

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Cytokinins2

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

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Abscissic acid

Abscissic Acid

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Abscissic acid1

Abscissic Acid

Source of production

  • Mature leaves

  • Seeds, roots

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Abscissic acid2

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

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Ethylene

Ethylene

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Ethylene1

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

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7 1 hormones4

7.1Hormones

  • 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

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Hormones

Hormones

  • Table 7.2: factors affecting hormone production

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Some practical implications of plant growth regulators

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

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Some practical implications of plant growth regulators1

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

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Some practical implications of plant growth regulators2

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

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Some practical implications of plant growth regulators3

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

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Some practical implications of plant growth regulators4

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

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Some practical implications of plant growth regulators5

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

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Some practical implications of plant growth regulators6

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

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Some practical implications of plant growth regulators7

Some Practical Implications of Plant Growth Regulators

  • Abscissic acid increases in proportion inducing véraison and the berry becomes a major sink

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Some practical implications of plant growth regulators8

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

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Some practical implications of plant growth regulators9

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

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Some practical implications of plant growth regulators10

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……

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Some practical implications of plant growth regulators11

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

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Some practical implications of plant growth regulators12

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'

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Hormones and initiation of inflorescence primordia

Hormones and Initiation of Inflorescence Primordia


Hormones and initiation of inflorescence primordia1

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

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Hormones and initiation of inflorescence primordia2

Hormones and Initiation of Inflorescence Primordia

  • The number size of inflorescences is the first indication of yield

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Yield components

Yield components

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Definitions

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

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Grape physiology

Buds

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Grape physiology

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

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Grape physiology

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Lateral or prompt bud

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

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Grape physiology

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Lateral or prompt bud1

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

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Lateral or prompt bud2

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'

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Compound buds

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

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Grape physiology

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Grape physiology

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Compound buds1

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

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Compound buds2

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.

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Compound buds3

Compound Buds

  • Environmental factors during bud development influence the potential crop in 18 months time

  • A major influence is light interception at the bud and the temperature; increased light and temperature has been shown to result in greater fruitfulness.

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Latent bud

Latentbud

  • These are buds that may be any type of bud that do not burst in the season that they are formed

  • Instead they remain dormant and viable and at some later stage may burst. Latent buds may take several seasons to burst, often as a result of vine damage or heavy pruning

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Grape physiology

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Bud initiation

Bud Initiation

  • Buds undergo differentiation

  • That is, primordial structures within the bud change depending on plant growth regulators that these structures receive

  • The level of plant growth regulators that the bud receives is dependant on climatic conditions during differentiation

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Bud initiation1

Bud Initiation

  • Differentiation coincides with flowering

  • And the slowing down of vegetative growth

  • Very sensitive to water stress

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Bud initiation2

Bud Initiation

  • Anlagen is a primordia that can become

  • Inflorescences

    • Repeated branching

  • Tendrils

    • Few branches

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The effect of plant growth regulators gibberellins

The Effect of Plant Growth RegulatorsGibberellins

  • Enhance initiation of anlagen

  • Encourage tendril formation as opposed to inflorescence formation

  • Recall…

  • Promote cell elongation so

  • Possibly a mechanism to promote vegetative growth over reproductive?

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The effect of plant growth regulators cytokinnins

The Effect of Plant Growth RegulatorsCytokinnins

  • Enhance initiation of anlagen

  • Encourage inflorescence formation as opposed to tendril formation

  • Recall…

  • Promote cell division

  • Produced in warm conditions

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The effect of plant growth regulators abscissic acid

The Effect of Plant Growth RegulatorsAbscissic Acid

  • Discourage the initiation of anlagen

  • Recall…

  • Produced by the roots in response to water stress

  • The process is very sensitive to water stress

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