Understanding How Fruit Trees Work

“Reviewing the Fundamentals”

Ted DeJong

The Fundamentals:

The overall objective of all cropping systems is to

maximize resource capture and optimize resource

use to achieve sustainable economic yields.

What resources are we mainly interested in?

• light energy• carbon • oxygen • water • nutrients

What are the three most

prominent chemical

elements in dry plant

parts?

Carbon C

Hydrogen H

Oxygen O

(Roughly in a ratio of

40:7:53)

Where does all that C H O

come from?

PHOTOSYNTHESIS!

The basic photosynthesis/respiration reactions(the most important processes for supporting life on the planet)

Carbohydrates + Oxygen(H2O) (CO2) (CH2O)n (O2 )

Photosynthesis

Respiration

Solar energy

absorbed by

chlorophyll

Chemical energy

To build and repair

Water + Carbon dioxide

Plants, nature’s

original solar energy

collectors

• What are nature’s natural

solar energy cells?

• Chloroplasts

• Problem: chloroplasts need an aqueous environment to function, air is dry and CO2

from air is required for photosynthesis.

• Solution: leaves with waxy cuticle to prevent dehydration and air control vents called stomates.

The primary function of tree structure is to support and

display leaves and the sole function of leaves is to house

and display chloroplasts for solar energy collection.

Carrying out photosynthesis is always a compromise between

taking up CO2 and losing H20.

Under non-stress conditions, canopy photosynthesis is a

direct function of the light intercepted by the canopy during

a day.

Rosati, et al. 2002. Acta Hort. 584: 89-94

Waln

uts

A

lmon

ds

Light interception

(that drives

photosynthesis) is

related to crop yield

but why then is there

so much scatter in all

of these points?

Lampinen, et al.,2012

Carbon distribution within the tree

The translocated

CH2O’s are mainly

sorbitol, sucrose and

glucose in almond

trees.

(This is a conceptual

diagram of where the

CH2O’s go but how

does that happen?)

What determines how and where CHO’s are used within

the tree?

This is a question that has received much attention over the past

50 years and scientists still disagree about it.

However, I believe it is relatively simple.

Carbon distribution is mainly controlled by the development and

growth patterns of individual organs and their ability to compete for

CH2O’s.

• A tree is a collection of semi-autonomous organs and each organ type has an organ- specific developmental pattern and growth potential.

• Organ growth is activated by endogenous and/or environmental signals.

• Once activated, environmental conditions and genetics determine conditional organ growth capacity.

• Realized organ growth for a given time interval is a consequence of organ growth capacity, resource availability and inter-organ competition for resources.

• Inter-organ competition for CH2Os is a function of location relative to sources and sinks of CH2Os, transport resistances, organ sink efficiency and organ microenvironment.

Bottom line: The tree does not allocate CH2Os to organs, organ growth and respiration takes it from the tree.

practical

examples of this

concept at work

is this type of

tree.

Five cultivars on one tree

Five cultivars on one tree.

What does this carbon distribution look like

through time as the plant grows?

Results from a new, 3-dimensional computer graphics based simulation

model called

L-PEACH

L-Peach Model

Input data

(Lpeach parameters)

Model components Output data

Hourly

Solar radiation

Temperature

Humidity

Irrigation

3D visualizatio

n

(L-STUDIO)

Quantitative data

(LPeachGraphing)

Architectural model

Commercial practices

CH2O and

H2O transport

algorithms

Functionality

of model

components

If we think of the tree as a collection of semi-

autonomous parts, what are the main parts of a

tree that we need to worry about from a CHO sink

point of view?

• Shoot growth

- both annual and daily

• Trunk growth

• Root growth

• Carbohydrate storage

• Fruit growth

In peach, length growth of

most shoots except water

sprouts (epicormic shoots) is

finished by June.

This is different in almonds.

Date

4/1/10 5/1/10 6/1/10 7/1/10 8/1/10 9/1/10

Leng

th (c

m)

0

20

40

60

80

100

high

medium

low

date

4/1/10 5/1/10 6/1/10 7/1/10 8/1/10 9/1/10

grow

th ra

te (c

m d

ay -1

)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

high

medium

low

Seasonal patterns of proleptic

almond shoot growth at three rates

of irrigation.

Note that shoot growth slowed down

by June but then there was a

second flush but addition of nodes

was more continuous.

date

4/1/2010 5/1/2010 6/1/2010 7/1/2010 8/1/2010 9/1/2010nu

mbe

r of n

odes

0

10

20

30

40

50

60

70

80

Contrary to popular opinion,

shoots grow most rapidly in

the afternoon when

temperatures are high and

stem water potential is

recovering form a daily

minimum.

Trunk diameter

growth continues

through most of

the growing

season.

Root growth tends to be

episodic in many species.

There is usually a burst of

activity in spring, a lull in mid-

summer and a second burst

in fall.

Peach example.

(mini-rhizotron data)

Mini-rhizotron data for walnut roots

Calendar day

80 100 120 140 160 180 200 220

Fru

it fr

esh

mas

s (g

/ fr

uit)

0

50

100

150

200

250

Control: no fertilizer applied

Spring N: 200 kg·ha-1

N applied April 1994

Fall N: 200 kg·ha-1

N applied September 1993

Split N: 100 kg·ha-1

N applied September 1993

+ 100 kg·ha-1

N applied April 1994

Peach Apple Almond

Describing fruit growth potentials

Re

lative

Gro

wth

Ra

te

(Co

mp

oun

d inte

rest ra

te)

The potential growth rate of all of

these fruit types can be predicted with

a relative growth rate (decreasing

compound interest rate) function.

Shoot and root biomass

CHO storage in shoots and roots

Fruit biomass

Canopy C assimilation

Supply

functions

Dem

and

functions

The L-Almond model

calculates all the

carbohydrate supply and

demand functions for each

hour of a day.

The model indicates that the

period corresponding to early

fruitlet growth is a time when

carbohydrate availability may

be particularly limiting.

This explains why there is a

fruit drop/abortion period in

late April/May/or early June

in many fruit species.

1 2 3 4 5 6 7 8 9 10

0.20.40.60.8

1 2 3 4 5 6 7 8 9 10

0.20.40.60.8

1 2 3 4 5 6 7 8 9 10

0.20.40.60.8

1 2 3 4 5 6 7 8 9 10

0.20.40.60.8

1 2 3 4 5 6 7 8 9 1000.20.40.60.8

Fra

ction o

f fr

uit d

istr

ibution into

cla

sses

Fruit dry weight classes

Unthinned887 fruits tree -1

Thinned 90 days after bloom

Thinned 60 days after bloom

Thinned 30 days after bloom

Thinned at bloom

220 fruits tree -1

220 fruits tree -1

220 fruits tree -1

220 fruits tree -1

0 50 100 150 200 250 300 350 400

75

100

125

150

175

200

225

250250

Crop load (no. fruits tree-1

)

Fru

it av

erag

e fr

esh

mas

s (g

frui

t -1)

5

10

15

20

25

30

35

4040

Tot

al C

rop

fres

h yi

eld

(Kg

tree

-1)

Fruit average fresh massTotal Crop fresh yield

Effect of crop load on fruit growth and crop yield

1 2 3 4 5 6 7 8 9 10

0.1

0.2

0.3

0.4

0.5

1 2 3 4 5 6 7 8 9 10

0.1

0.2

0.3

0.4

0.5

1 2 3 4 5 6 7 8 9 10

0.1

0.2

0.3

0.4

0.5

1 2 3 4 5 6 7 8 9 10

0.1

0.2

0.3

0.4

0.5

1 2 3 4 5 6 7 8 9 100

0.1

0.2

0.3

0.4

0.5

Fruit fresh mass classes

Fra

ctio

n of

frui

t in

clas

s

n = 350

n = 250

n = 200

n = 100

n = 40

Classes (g)

1 = < 30

2 = 30 - 60

3 = 60 - 90

4 = 90 - 120

5 = 120 - 150

6 = 150 - 180

7 = 180 - 210

8 = 210 - 240

9 = 240 - 270

10 = > 270

Thanks for your attention!

Questions?