The National Wine and Grape Industry Centre is a research centre within Charles Sturt University in alliance with the Department of Primary Industries NSW and the NSW Wine Industry Association www.csu.edu.au/nwgic

Vine balance, from a mechanistic perspective, can be considered as a source-sink relationship, i.e. the relationship between carbohydrate supply (via canopy photosynthesis) and the

carbohydrate requirement of the developing fruit. Manipulating vine balance potentially affects the availability of carbohydrates to support berry development. However, when photosynthetic

capacity is manipulated through canopy architecture or management practices, bunch exposure can also be affected. Identifying which factor has the greater influence on berry composition is

therefore difficult under field conditions. To specifically manipulate whole vine carbohydrate availability, and in turn provide control over the rate of berry sugar accumulation, an experimental

approach was developed to reduce photosynthesis by supplying whole vines with air at CO2 concentrations below ambient levels. This poster reports on the design and testing of this system,

and the results of the first experiment which examined the impact of low post-veraison carbohydrate supply on berry sugar accumulation and composition.

Introduction

Targeted manipulation of vine balance 2.

A whole-vine chamber system for controlling berry sugar accumulation.

Jason SMITH 1,5, Everard EDWARDS 2, Julia GOUOT 1,

Celia BARRIL1,3, Amanda WALKER 2 and Bruno HOLZAPFEL 1,4 1 National Wine and Grape Industry Centre, Wagga Wagga, Australia.

2 CSIRO Agriculture, Waite Campus, Adelaide, Australia. 3 School of Agricultural and Wine Sciences, Charles Sturt University Wagga Wagga, Australia.

4 New South Wales Department of Primary Industries, Wagga Wagga, Australia

5 Current address: Hochschule Geisenheim University, Germany.

Whole vine chamber system for Low CO2 mediated reduction of canopy photosynthesis

The experimental system consisted of six acrylic chambers, each with a volume of 1.2 cubic metres, that were built to enclose

large pot-grown fruiting grapevines. The acrylic chambers, and plastic base which housed fans, speed controller and air

intakes, were built with two halves to allow installation from each side of cordon trained vines. Air scrubbers, with an

additional variable speed fan and 27 kg of soda-lime, were used to reduce the CO2 concentration of supply air to three

chambers by approximately 200 ppm compared to ambient air supplied to three non-scrubbed control chambers.

Results and discussion

To determine the response of berry sugar accumulation to low photosynthetic carbohydrate

supply during berry ripening, the chambers were installed on six Shiraz grapevines at the

onset of veraison in 2015. All chambers were run at Ambient CO2 for 2 days to record initial

photosynthesis rates, and then Low CO2 treatment commenced at the beginning of the

third day and ran for a period of 27 days before the chambers were returned to Ambient

CO2 concentration until harvest. A summary of basic vine and chamber parameters is shown

in Table 1 below.

The CO2 concentration of incoming and outgoing air was monitored sequentially at 30 second intervals over a period of 5

minutes with a multiplexed infrared gas analyser. All six chambers were measured over a 30 minute cycle, providing a

continuous series of CO2 concentration readings (Fig. 1a). Calculations of whole vine photosynthesis, which used the CO2

inlet/outlet differential from these data, air flow rate and leaf area, showed that that the photosynthetic capacity of the low

CO2 treatment was reduced by approximately 50% compared to control vines (Fig. 1b). Water vapour concentrations (data not

shown) and chamber air temperature was also recorded.

Figure 1: Measurement of inlet and outlet CO2 concentration of six gas exchange

chambers over a 30 minute cycle (a), and subsequent whole vine average photosynthesis

rates over a sample five day period in Summer 2014 (b).

Materials and Methods

a)

Minutes

0 5 10 15 20 25 30

Air C

O2 c

on

ce

ntr

atio

n (

pp

m)

0

100

200

300

400

500

Ambient CO2 chamber readings

Low CO2 chamber readings

Transition / between chambers

b)

Days

1 2 3 4 5

Ph

oto

synth

esis

ra

te (

um

ol m

-2 s

-1)

-4

-2

0

2

4

6

8

10

12

14

Chamber 1

Chamber 2

Chamber 3 Chamber 4

Chamber 5 Chamber 6

Ambient CO2 treatment Low CO2 treatment

INOUT

IN

OUT

IN

OUT

IN

OUT

INOUT

INOUT

A sample of 50 berries was collected from each chamber on seven dates through the period

when both Ambient and Low CO2 treatments were running. Additional samples were

collected before and after the low CO2 treatment period, and also at harvest when fruit

reached an approximate sugar content of 24 oBrix. The berries were weighed and a juice

sample collected and frozen at -80oC. Soluble solids were recorded with a digital

refractometer, and the concentration of glucose and fructose by HPLC.

Acknowledgements

The authors would like to thank David Foster, Sebastian Holzapfel and Ginger Korosi for technical support or assistance during the experiments. This work was supported by Wine Australia, CSIRO, the National Wine and Grape Industry Centre and Wine Australia.

Chambers Vines

CO2

(ppm)

Temp

(oC)

Leaf

Area

(m2)

Yield

(kg)

Pruning

weight

(kg)

Ravaz

index

Amb

CO2

382 23.8 4.8 5.8 0.63 9.4

Low

CO2

200 24.4 4.9 4.5 0.63 7.1

Table 1: Summary of basic chamber conditions during the 27 day low

CO2 treatment, and vine canopy and yield parameters.

Conclusions

a)

27 Dec 6 Jan 16 Jan 26 Jan 5 Jan 15 Jan 25 Jan 7 Jan

Juic

e s

olu

ble

solid

s (

obrix)

10

13

16

19

22

26

Juic

e g

lucose +

fru

cto

se (

mg/L

)

80

120

160

200

240

280

Ambient CO2

Low CO2 pre-/post-treatment

Low CO2 during treatment

CO2 scrubbing period

Harvest

Ambient CO2

Harvest

Low CO2

b)

27 Dec 6 Jan 16 Jan 26 Jan 5 Jan 15 Jan 25 Jan 7 Jan

Sugar

per

berr

y (

g)

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

27 Dec 6 Jan 16 Jan26 Jan 5 Jan 15 Jan25 Jan 7 Jan

Be

rry F

W (

g)

1.0

1.2

1.4

1.6

1.8

2.0

Harvest

Low CO2

Harvest

Ambient CO2

y = 0.0061x-256

y = 0.0034x-144

Figure 2: Effect of Low CO2 mediated reduction in whole canopy photosynthesis on juice sugar concentrations (a), and sugar per

berry during the post-veraison period of the 2014/15 season (b). Error bars ± SE mean (n=3), with individual vines shown for harvest.

During the 27 day period when the Low CO2 treatment was running, juice soluble solids in

the Ambient CO2 control treatment increased from 11.6 to 19.2 obrix. In the corresponding

period, berries in the Low CO2 treatment only reached 15.5 obrix (Fig. 2a). On a per berry

basis, the rate of sugar accumulation was reduced from 6.1 to 3.4 mg day-1 in the Low CO2

treatment (Fig. 2b). The reduction in sugar accumulation was therefore proportional to the

reduction in photosynthesis. Berry weight loss was not influenced by low CO2, but in both

treatments weight loss and continued berry sugar accumulation contributed the increase

in sugar concentration in the later part of ripening. By delaying harvest of previously Low

CO2 supplied vines an average of 15 days, the same juice sugar values were obtained as for

control vines.

Reducing the CO2 concentration of air supplied to whole potted grapevines in transparent

chambers caused a proportional reduction in whole photosynthesis, and in turn a

proportional reduction in the rate of berry sugar accumulation. These findings show that

CO2 mediated control of vine photosynthesis provides an effective tool for targeted

manipulation of the rate of berry sugar accumulation. While vine balance is subjective

term and difficult to properly quantify or study, this system provides an opportunity to

specifically determine the impact of carbohydrate supply on fruit and wine composition.