COMPETITION AMONG VEGETATIVE AND REPRODUCTIVE CYCLES AND ROLE OF PRUNING. Musacchi, S.

Transcription

1 COMPETITION AMONG VEGETATIVE AND REPRODUCTIVE CYCLES AND ROLE OF PRUNING Musacchi, S. Washington State University, TFREC, Wenatchee, WA KEYWORDS pruning, dry matter (DM), competition, source, sink, flower bud, vegetative bud, thinning, anthesis, girdling, notching, bending, root pruning. ABSTRACT Vegetative and reproductive cycles in fruit trees overlap and generate a series of competitions among the various organs. Understanding the factors generating competition within the tree can improve the orchard management. The subjects covered in the presentation will be: physiological basis of vegetative and reproductive cycles, overlap of the two cycles, source-sink theory, dry matter (DM) partition, competitions among tree organs, and role of pruning in apple and pear orchards. Trees perform activities which are closely related such as: canopy and roots development, reproductive development (from flower bud differentiation up to fruit maturity) and reserves accumulation. Active growing organs (fruit and shoot tips) are typically strong attraction centers ( sink ) for photosynthesis products generated in the leaves ( source ) and nutrients. The sink strength seems to depend on the ratio between the different endogenous hormones involved. Pruning is a pool of practices that allow control of the tree growth and maximize the orchard income. Growth leads to a modification of the tree shape and/or dimension and occurs only when DM increases. Net total DM of an apple orchard is a function of incident solar radiation availability (independent of the production system) and light interception (training system-depending and the main factor limiting orchard productivity). The rootstock can affect the scion development by influencing various parameters: photosynthetic efficiency, speed and duration of growth, apical dominance, leaf area, leaf senescence, assimilates allocation and vigor. Main competitions between organs are: roots/shoots, shoots/buds formation, shoots/fruit, fruit development/shoots, seeds/flower buds, fruits in the same cluster, and shoots in a different position. Pruning can alter these competitions and therefore modify the gradient from vegetative to reproductive.

2 Competition among vegetative and reproductive cycles and role of pruning Associate Professor & Endowed Chair Tree Fruit Physiology and Management Washington State University Tree Fruit Research and Extension Center (TFREC) 1100 N. Western Ave., Wenatchee November 17, 2015 Wenatchee 2015 WSU Fruit School

3 a) The manipulation of fruiting b) Physiological basis of vegetative and reproductive cycles c) Overlap of the two cycles d) Source-sink e) Dry matter Outline of presentation f) Competitions among tree organs g) Role of the pruning in the regulation of the relationship between vegetation and production h) Pruning techniques

4 Why we need to manipulate fruiting? a) To modify the balance between growth and fruiting, to increase yield and reduce management costs associated with large canopy tree; b) To improve flowering and fruit set; c) To reduce the numbers of fruit; d) To modify the season of flowering and fruiting or the post-harvest storage characteristic of the fruit. Jackson, 1989

5 Tree is a collection of individual sinks all related and often in competition. Bloom Fruit set Fruit development Fruit ripening Vegetative growth Flower bud formation Flower development Costa et al., 1986

6 Vegetative activity Vegetative and reproductive cycles: Reproductive activity Flower bud induction Flower bud differentiation Bloom, and fruit fruit development and development ripening Canopy Root Bloom, fruit development and ripening Flower bud induction Costa et al., 1986

7 PRODUCTIVITY Crop productivity is depending upon the ability of a plant to produce high levels of photosynthates and to allocate a high proportion of them in economically important organs. Water content is also an important component of the total yield. To maximize yield, fruit need to attract photosynthetic assimilates, mineral nutrients and water. Wright, 1989

8 Can be considered as a collection of individual sinks which compete with each other. During plant growth these sinks will change in competitive ability leading to diversion of assimilates. Examples: Reduction of vegetative growth by developing fruit Reduction of fruit growth by developing vegetative sinks Competition between individual fruit sinks; Effect of fruiting on flower initiation. Wright, 1989 Trees

9 SOURCE-SINK The organs actively growing (fruit and shoot tip) are typically strong centers of attraction of the products of photosynthesis and nutrients. The strength of a sink seems to depend on the ratio between the various endogenous hormones. (Hansen, 1987)

10 SOURCE-SINK Order of priority of the various sink: High Low Seed > Fruit= Shoot apex and leaves> Cambium> Roots> Reserves It is not clear if the competition is for photosynthates, nutrients, water or other growth factors. Cannell, 1985

11 Pruning Is a pool of practices that permit the control of growth and maximize the income in the orchard. Pruning modifies the tree growth and the balance between production and growth.

12 Physiological basis of pruning Growth is a modification of the shape or dimension of the tree. More in details: growth occurs only when the dry matter increases.

13 DRY MATTER Net total DM of an apple orchard is a function of: light availability, Incident solar radiation is independent of production system (dep. on climate). light interception (is the main factor limiting orchard productivity) PPF (photosynthetic photon flux) intercepted by an apple orchard depend on: Orchard design Leaf area index Length of growing season photosynthesis respiration (Wünsche et al., 1996).

14 Tree with heavy crop load has a dramatic reduction of vegetative growth (Murneek, 1924). A reduction of dry matter partitioning to shoot, leaves and roots due to fruiting has been demonstrated in a wide number of crops (Maggs, 1963; Avery, 1970; Hansen, 1971).

15 % of dry matter Distribution of dry matter Tree organs: Fruit Branches Root Trunk area circumference (cm)

16 The presence of fruit limits the production and the accumulation of dry matter in the trunk and especially in the roots, but it stimulates the production of total dry matter. However, if high levels of crop are induced for two consecutive years, the total dry matter production will be reduced and particularly root growth decreases. (Lenz, 1986) Fruit Leaves Shoots Trunk Roots Effect of crop load on Golden delicious grafted on M9 Dry matter/tree (kg)

17 Seasonal leaf area development: pattern of canopy changes over the first 3 yrs after planting.

18 Effect of planting density on light interception HDP intercepted > 80% PAR Palmer, trees/ha

19 Rootstocks role The rootstock can affect the development of the scion by changing various parameters: photosynthetic efficiency speed and duration of growth apical dominance leaves size leaf senescence distribution of assimilates vigor

20 Rootstocks and dry matter The amount of dry matter intended to fruits in trees grafted on a dwarfing rootstocks like M9 is over 70%, while in the case of a vigorous rootstock this amount does not reach 50% (MM106). Barlow and Smith, 1971; Hansen, 1980

21 Competitions among tree organs

22 Main competition between organs: 1. Root/shoot 2. Shoot/ bud formation 3. Shoot/fruit 4. Fruit development/shoot 5. Seed/flower bud 6. Fruit in the same cluster 7. Shoot in a different position

23 1) Root/Shoot growth Black line = root growth dashed line = Shoot growth ROOTS SHOOTS Baldini, 1986

24 Shoot growth The maximum LAI (Leaf Area Index) during a growning season are achived in a faster way when the tree have a high number of vegetative points. Time Number of flower buds

25 2) Shoot/ bud formation There is a strong anthagonism among shoot growth and flower bud formation. Flower bud formation is maximum when the shoot stops to grow.

26 2) Shoot/ bud formation Hormones are controlling this competition because young leaves produce IAA e GA that can interfere with the reproductive activity increasing the competition for nutrients. GAs have a direct action because they have an Shoot antiflorigen activity and stop lenght the flower bud formation. The rate of flower bud differentiation increases concurrently with the reduction of shoot elongation. Number of flower bud/ Total buds number Giulivo et al., 1981 Costa et al., 1986

27 3) SHOOT/FRUIT Physiological drops are mainly due to the competition between shoots and fruit. Fruit initially are weak sink and there is a selection process. Only fruit that can compete with shoot can be maintained on the tree. Hormones can influence the competition because they are controlling nutrients translocation.

28 Fruit speed of growth and physiological fruit drop Growth speed June drop Costa et al., 1986

29 4) Fruit development A positive role is played by IAA, GA and CK. Hormones level IAA Fruit growth IAA and GA exhibit their action during the cytokinesis. GA Fruit size increase IAA stimulates the fruit growth by the accumulation of metabolites. Baldini, 1986 CK Time Baldini, 1986

30 5) SEED/FLOWER BUD FORMATION Too many seeds can induce an inhibition on flower buds formation due to the high level of GAs synthesized in the endosperm and in the embryo. If the number of seeds is to high we can have an alternative bearing. STONE FRUIT POME FRUIT

31 ALTERNATIVE BEARING Baldini, 1986 Baldini, 1986

32 Assimilate partitioning The presence of seeds and fruit causes a large change in the distribution of assimilates. Fruit development can reduce or even stop root growth. (Wright, 1989)

33 UPTAKE of mineral elements It has been shown that in some species, such as apple, trees with fruits showed a higher concentration of mineral elements in leaves compared to those devoid of fruits. Cannel, 1985

34 Photosynthesis Trees with fruit are able to produce more dry matter per unit area of leaf than the plants which do not bear fruit. This suggests that the fruiting increases the photosynthetic efficiency. Maggs, 1963

35 Water relations Even for the water, Lenz (1986) has shown that in trees with fruit transpiration is double compared to the condition of fruits absence. Fruiting tree have a higher stomatal conductance. (Jones and Cummings, 1984)

36 6) FRUIT IN THE SAME CLUSTER i.e. king flower in apple and basal flower in pear are more developed

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38 7) Shoots in different positions i.e. shoot in an apical position grows more compare to the others (apical dominance). Grisvard, 1957

39 TIRA SAVIA

40 Role of the pruning in the regulation of the relationship between vegetation and production

41 PRUNING ROLE IN THE BALANCE BETWEEN VEGETATIVE AND REPRODUCTIVE ACTIVITY Vegetative activity Reproductive activity Hilkenbaumer, 1953

42 Bending shoot can change the balance between vegetative and reproductive activity

43 Bending shoot can change the balance between vegetative and reproductive activity Vegetative activity Reproductive activity Hilkenbaumer, 1953

44 Growth capacity of buds with different orientations Grisvard, 1957

45 Effect of bending Grisvard, 1957 Mohacsy, 1957

46 Position of a branch can change with age Grisvard, 1957

47 Modification due to aging Young tree Adult tree Costa et al., 1986 Senescent tree Old tree

48 Tree balance Training system Rootstock ORGANS FUNCTION Pruning Leaves Carbohydrate production Growth regulator Fruits Attractor, hormone producer Adsorbing roots Vascular system Transportation Water and nutrient up take, hormone producer Nutrition Root pruning Irrigation

49 Orchard Pruning Pruning technique Root pruning Trunk cutting

50 Main pruning techniques Pinching Girdling Notching Bending

51 Pinching

52 Girdling: Precise shoots formation Girdling, notching and Promalin application can help to promote shoot growth

53 Notching

54 Notching: Precise shoots formation

55 Notching: Precise shoots formation

56 Flower bud removal: Precise shoots formation

57 Bending

58 Diapo 71 bending

59 Gradient of vigor Baldini,1986

60 Gradient of vigor Baldini,1986

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62 Pruning technique for high density orchard (HDP)

63 Effect of Dutch cut

64 Pruning of the top part of the branches in spindle

65 Trunk cut back to enhance shoots formation

66 Shoots in the upper part try to replace the leader. We have to eliminate the concurrent

67 «Pull out» technique

68 Cut back on lateral 1-yearold shoot with a flower bud Cut back of the top on 1- year-old shoot

69 Root pruning

70 Root pruning: How? When? Blade straight, in vertical position Blade straight, Blade curve

71 Abbé Fétel: winter cut end of February in medium-high planting density orchards 20 cm cm

72 Vertical root pruning

73 Abbé Fétel: winter cut end of February in very and ultra high planting density orchards 35cm 70 cm 45

74 Angle root pruning

75 ROOT PRUNING EFFETCS Control Cutted two sides in winter

76 EFFECT OF ROOT PRUNING ON FLOWER BUD FORMATION

77 What does root pruning do? If the strong roots are pruned less uptake of water If the fine roots are pruned less uptake of nutrients Changing the hormonal balance less cytokinines reduced shoot growth Vercammen, 2005

78 Flower bud formation 2001 Source: Frank Maas- Wageningen Olanda

79 Decision scheme Flower buds Spring Fruit set Vercammen,2005

80 Trunk cutting

81 Trunk cutting

82 YouTube Videos WSU CAHNRS Channel; WSU Tree Fruit playlist Recorded and Being Edited: Pruning Bartlett Pears to Optimize Fruit Size and Quality (Musacchi) WSU Expert Videos Direct link to the WSU Tree Fruit playlist: ddqu

83 Thanks for the attention!!

84 Stefano Musacchi Associate Professor Endowed Chair Tree Fruit Physiology and Management Washington State University Tree Fruit Research and Extension Center (TFREC) 1100 N. Western Ave. Wenatchee, WA Phone: (509)