palestra j palmer

The New Zealand Institute for Plant & Food Research Limited

Plant physiology as a tool of productivity in different orchard systems

John Palmer, Plant & Food Research Ltd., Motueka Research Centre, New Zealand


Kerikeri 35o S

Auckland

Ruakura Te Puke

Hawke’s Bay

Marlborough

Lincoln

Nelson

Clyde 45o S

Palmerston North

Plant & Food Research


A Crown Research Institute


I began my career in pipfruit physiology over 40 years ago at East Malling Research Station, England.

Over those 40 years I have been privileged to work with and to know many of the leading pipfruit physiologists all over the world. Ours is very much a world wide community, like all science we advance by an interaction of ideas, tempered by our own environment.

And that environment includes, not only the physical environment, but the grower community and the funding opportunities and limitations.


Crop physiology is all about understanding the processes that control and determine plant growth and development.

Horticulture is all about plant manipulation to achieve desired ends. Physiological understanding enables us to predictably manipulate our plants.

Classically, for example, the understanding of the effect of daylength on flowering has enabled the glasshouse flower industry to reliably programme the production of flowers and flowering pot plants.


Fruit development pathway

Flower evocation

Flower differentiation

Flowering

Fertilisation

Fruit growth

Fruit maturation

Fruit harvest

Fruit storage &distribution

Consumer


Orchard development pathway

Choice of cultivar

Choice of rootstock

Tree spacing

Tree quality

Tree training

Early yield and fruit quality

Mature yield and fruit quality


Key developments over the last 40 years

I believe that physiology has played, is playing and will play a key role in the future of fruit growing.

In this talk I will inevitably be selective in the examples I use of the contribution of physiology. Many of those examples I have been involved in, but I choose them just because I am so familiar with them. Other speakers will cover other key physiological contributions in their presentations.


Key developments

1. The importance of light interception and distribution and the link to yield and fruit quality.

2. The widespread adoption of intensive planting on dwarfing rootstocks.

3. An understanding of the orchard as a system.

4. A general move away from pruning to branch manipulation.

5. The use of computer models to aid decision making.

6. The use of PGRs in nursery and orchard.

7. The need to apply physiological understanding to new cultivars.


Key developments






6. The use of PGRs.



Key developments






6. The use of PGRs in nursery and orchard.



Presentation overview

1) Tree manipulation

2) Carbon acquisition- light into dry matter

3) Carbon partitioning- total dry matter to fruit dry matter

4) Fruit quality- fruit dry matter into saleable product

5) Where to from here?


Tree manipulation in the Tree manipulation in the nursery and the orchardnursery and the orchard


Tree manipulation in the nursery and the orchard with PGRs

Interest in feathering agents to induce sylleptic branching began in the USA and in Europe in the 1970s (Max Williams, Jim Quinlan, Bob Wertheim).

The physiological understanding underpinning this was that the apex suppressed lateral bud development but application of materials to either slow the development of the apex or increase the supply of cytokinins to the lateral buds would induce axillary bud development.

This resulted in the release of products such as Promalin, benzyladenine and recently Tiberon.


A well-feathered tree of ‘Braeburn’/M.9


Effect of concentration and frequency of application of BA sprays on ‘Fuji’/MM.106

BA concn. mg L-1

Number of feathers

Total length of feathers (m)

Mean feather length (cm)

Control 0 1.0 0.6 62 4 sprays 100 4.3 1.9 47 200 8.8 2.5 25 400 12.0 3.3 27 6 sprays 100 6.9 2.1 29 200 13.4 3.7 26 400 15.9 4.1 25 5% LSD 2.78* 1.43* 12.9 * for comparisons within treatments, excluding control

Sprays applied weekly


Effect of repeat sprays of BA followed by repeat sprays of GAs on the number of

feathers on ‘Comice’/QC

Gibberellin sprays BA sprays None 200 mg L-1

GA4+7

400 mg L-1 GA4+7

200 mg L-1 GA3

400 mg L-1 GA3

None 0.9 14.1 16.6 15.7 17.0 750 mg L-1 BA 2.4 12.9 15.3 15.8 17.4 1500 mg L-1 BA 3.5 10.4 10.2 12.7 16.8 Mean 2.5 12.1 13.5 14.5 17.1 P for main effect of BA spray = <0.001; P for main effect of GA spray = <0.001; P for interaction = 0.001

(Simplified from Palmer et al. 2010)4 weekly sprays of BA followed by4 weekly sprays of GA


Young ‘Scifresh’/M.9 treeshowing typical barewood


Excessive axillary flowering, with poor quality spurs, particularly towards the base of the shoot


Tree manipulation in relation to barewood

1) Prevention of flowering on one-year-old wood on newly planted trees in the orchard by using GA sprays in the nursery

2) Reinvigoration of blind buds in the orchard using local application of thidiazuron

In both cases we were using physiological understanding in our approach to this problem


Effects of GA on floweringand subsequent spur development

• GA3 at 400 mg l-1 applied on 3 January and 30 January on trees in their last season in the nursery, resulted in a 46% reduction in flowering the following spring.

• One year later the treated trees showed a 41% increase in density of spur and terminal flower clusters along the feathers.

• So by reducing the axillary flowering, we had allowed vegetative buds to develop into spurs.


Extinct spurs

Blind buds


Effect of timing, product and concentration on % envigorated buds of ‘Scifresh’/M.9

BA = benzyladenine, TDZ = thidiazuron

Spray Conc. Weeks in relation to bud break Mean (mg l-1) -2 0 +2 +4 Control 6 BA 500 7 5 9 8 7 BA 2500 3 8 10 7 7 TDZ 500 26 13 8 7 12 TDZ 2500 79 64 69 54 66 Mean 21 17 20 15

P for effect of chemical = <0.001: P for effect of timing = 0.100; P for interaction = 0.004 Simplified from Palmer et al. (2005)


TDZ (2500ppm) applied 3.5 weeks before budbreaktaken 7.7 weeks after treatment.


Treated on the left with 2500 mg L-1

TDZ the previous year.

Untreated on the right.


Carbon acquisition:Carbon acquisition:light into total dry matterlight into total dry matter


The whole apple tree responds dynamically to changes in incident light

6 7 8 9 10 11 12 13 14 15 16 17 18 19 200

1

2

3

4

5

6

7

8

0

100

200

300

400 CO2 uptake Solar radiation

CO

2 exc

hang

e ra

te g

h-1

Time of day

Inci

dent

sol

ar ra

diat

ion

PA

R (W

m-2)


0.0 0.5 1.0 1.50

5

10

15

20

25

sugar beet

potatoes

barley

apples

Tota

l dry

mat

ter p

rodu

ctio

n (t

ha-1)

Intercepted solar radiation (GJ m-2)

Relationship between intercepted solar radiation anddry matter production

Redrawn from Monteith (1977)


Seasonal pattern of light interception by ‘Fuji’/M.9 apple in New Zealand

0 30 60 90 120 150 180 210 240 2700

10

20

30

40

50

0

5

10

15

20

25

30

35

Ligh

t int

erce

ptio

n (%

)

Time from September 15 (days)

Mea

n 5

day

sola

r rad

iatio

n (M

J m

-2 d

-1)

Redrawn from Palmer et al. (2002)


Relationship between seasonal light interception and total dry matter production for apple

400 600 800 1000 1200 14000

5

10

15

20

25

30 Royal Gala Braeburn Fuji UK data

Light interception (MJ m-2 PAR)

Tota

l dry

mat

ter p

rodu

ctio

n (t

ha-1)

From Palmer et al. (2002)


Factors influencing light interception

Tree factors – how we capture the light1. leaf area index2. tree height3. row orientation4. tree width5. cultivar

Site factors – what light is available1. latitude 2. cloudiness 3. frost-free period


Relationship between LAI and light interception

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.50

10

20

30

40

50

60

70

80

90

100Li

ght i

nter

cept

ion

%

Leaf area index


Light interception has proved to be a very useful physiological tool to compare different production systems with different tree heights, row spacings and tree pruning and training treatments.

Light interception sets the upper limit for production.


Harvest index: Harvest index: total dry matter into fruit total dry matter into fruit

dry matterdry matter


Harvest index

Harvest index is the proportion of the total dry matter production harvested in the fruit.

It is determined primarily by:

1. crop load

2. the strength of the alternative sinks for carbohydrate, particularly vegetative vigour.


Effect of crop load on partitioning of dry matter of ‘Crispin’/M.27 apple trees.

Palmer, 1993

0 5 10 15 20 25

0

10

20

30

40

50

60

70

80

90

100

% d

ry m

atte

r inc

rem

ent

Number of fruit/leaf area (fruit m-2)

Fruit

Leaf

Wood

Root


Commercially, our harvest index may be less than that physiological possible because of:

1) young trees2) bienniality3) reduced crop load to achieve our

desired fruit size profile.


Effect of crop load on partitioning of dry matter into fruit, ‘Crispin’/M.27

30 40 50 60 70 80 90150

200

250

300

350

400

450M

ean

fruit

wei

ght (

g)

Partitioning to fruit (%)

Data of 1982 taken from Palmer (1992)


Nearly all of our recent changes to tree management have encouraged an increase in harvest index e.g.

1. dwarfing rootstocks 2. minimal pruning 3. tying down4. PGRs

All by reducing vegetative vigour.


Apple tree growth control by rootstocks


A two year old treeof ‘Peasgood Nonsuch’apple on M.27 rootstock, showing a very high harvest index


We can consistently achieve up to 70% harvest index, for trees at maturity.

Our limitations may be commercial or due to problems with bienniality.

I do not believe we have reached the limit of the biological system, particularly in relation to the speed at which we reach full production.

Harvest index


Fruit quality:Fruit quality:fruit dry matter into fruit dry matter into

saleable productsaleable product


Fruit quality:fruit dry matter into saleable product

This of course is the critical stage for we need to present the customer fruit that is attractive, with good texture and flavour that is typical of the cultivar.

We are now dealing with hydrated dry matter in a ready to eat, attractive, healthy, edible package.

There are, however, two key factors that we have to get right – light distribution and fruit dry matter concentration


Generalised effects of shade on apple fruit quality

Shade decreases:fruit weightfruit red coloursoluble solids concentrationbitter pit incidence and severitysunburnskin russetflower bud numbersfruit set


Shady business is therefore to be discouraged in the orchard, for more reasons than one!


However, intensive systems of production do not necessarily mean we avoid the problems of shading within our canopies.

Never forget the link between light and fruit quality.

Certainly one of the major drivers in the adoption of intensive systems has been the desire for better light distribution within our tree canopies.


‘Fiesta’/M.9 three-row bed


Shaded fruit within the canopy


Recent ways of manipulating light in the orchard

Reflective mulch

1. newer materials now available that can be run over with tractors.

2. importance of diffuse scattering.

Hail netting

1. need minimum shade coupled with effective hail control.

2. lighter colours increase scattered light.


The use and the misuse of light

High light interception is essential for high yield per hectare.

Good light distribution is essential for high quality fruit.

A successful system is one that combines both of these.

Maximum use with minimum misuse


Fruit dry matter and quality

The packaging of dry matter into a fresh fruit form is one of the most critical parts of fruit growing.

Although eye appeal remains important in many fruit, particularly colour and freedom from blemish, taste is becoming increasingly important. Initial purchase is based on eye appeal but repeat purchase is based on the eating experience.

Our production target should therefore be yield, fruit size, appearance AND eating quality (maturity and dry matter concentration).



Taste with apples has, until recently, largely been determined by fruit maturity, although for some cultivars a minimum soluble solids concentration is being specified.

Eating quality with apples is complex, as crispness and juiciness are vital requirements, as well as taste.

Each cultivar has its own characteristic texture, flavour and taste.



Carbohydrates (starch and sugars) and acids make up the major proportion of the fruit dry matter in many fleshy fruit.

Therefore the accumulation of carbohydrate into the fruit is the key process that determines the final fruit quality.

Traditionally, however, carbon acquisition and distribution have not been closely integratedinto the development of fruit quality.


Composition of the edible portion of several fruit (USDA website)

% of dry matter Fruit

Fruit dry matter

(%) Sugar + starch

Fibre

Apple 14 70 17 Kiwifruit 17 55 20 Pear 16 60 20 Apricot 14 70 15 Peach 11 75 13 Melon 10 80 8 Tomato 5.5 50 22


Royal Gala from 4 orchards in Nelson and four orchards in Hawke’s Bay

10 11 12 1311

12

13

14

Hawke's Bay Nelson

Sol

uble

sol

ids

afte

r 12

wee

ks s

tora

ge (o B

rix)

Soluble solids at harvest (oBrix)

r2 = 0.41




12 13 14 15 1610

11

12

13

14 Hawke's Bay Nelson

Solu

ble

solid

s at

har

vest

(o Brix

)

Dry matter concentration at harvest (%)

r2 = 0.32




12 13 14 15 1610

11

12

13


Solu

ble

solid

s af

ter 6

wee

ks s

tora

ge (o Br

ix)


r2 = 0.53




12 13 14 15 1610

11

12

13


Sol

uble

sol

ids

afte

r 12

wee

ks s

tora

ge (o B

rix)


r2 = 0.82



Relationship between fruit dry matter concentration and soluble solids after 12 weeks storage of ‘Royal Gala’ and ‘Scifresh’. Samples from Nelson and HB

13 14 15 16 17 1811

12

13

14

15

16

Solu

ble

solid

s (o Br

ix)

Fruit dry matter concentration (%)

Royal Gala Scifresh

r2 = 0.97



Apple fruit dry matter concentration (DMC) and soluble solids

Redrawn from McGlone et al. (2003)

‘Royal Gala’ fruit from 3 orchards and two picking dates

r2 = 0.93


Consumers’ scores for ‘Royal Gala’ apples from different DMC categories after 10–12 weeks of cool

storage.

Low Moderate High0

2

4

6

8

Liki

ng S

core

DMC Category

b b

a

Low Moderate High0

20

40

60

80

100

Acce

ptab

ility

%

DMC Category

bab

a

Low Moderate High0

20

40

60

80

100

Like

lihoo

d of

Pur

chas

e %

DMC Category

bb

a

From Palmer et al. 2010


Fruit quality and fruit maturity

The traditional harvest indices are indicators of harvest maturity; fruit DMC can be viewed as a complementary fruit quality index.

A high DMC fruit will only achieve its high sensory potential if it is harvested at the correct stage of maturity and then stored in a manner in which firmness and acidity are optimally conserved.


The control of DMC

If fruit dry matter concentration is a useful fruit quality index, then the key physiological question is then how do we control and manipulate it to achieve optimal fruit quality?


Key fluxes into and within apple fruit

Sor = sorbitolFru = fructoseGlu = glucoseSuc = sucrose


Where to from here?Where to from here?


Growing to product Growing to product specificationspecification


Future physiological challenges– precision horticulture

1. “Every bud counts”2. Improved rootstocks with resistance to biotic and

edaphic factors for apples and a range of dwarfing, easily propagated Pyrus rootstocks to revolutionise the pear industry.

3. Growing to product specification. Consistent high fruit quality at point of sale, with greater emphasis on eating quality rather than cosmetic appearance.

4. Increased development of multidisciplinary teams including molecular biologists.

5. Orchard systems in a wider context.


Our traditional view of the orchard system

Modified from Bruce Barritt


Our enlarged view of the orchard system

Sustainability

Carbon footprint

Water footprint


SummarySummary

I believe physiology has aided the development of fruit growing in many ways, as I hope this presentation has illustrated.

But the challenges that are currently with us and will present themselves in the future will require even more physiological input. Our fruit growing industries need to continue to produce desirable, healthy, saleable fruit, produced in sustainable, reliable and predictable ways.

Only by understanding the way in which the tree dynamically responds to its environment and its own internal regulation can we achieve those goals.



www.plantandfood.com

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Thank you

palestra j palmer

Technology

new cultivars

plant manipulation

o sthe new zealand institute

physiological understanding

use of pgrs

key developments1

use of computer models

motueka research centre