Assimilate allocation and carbon reserves in Juglans regia L. seedlings

HAL Id: hal-02720090

https://hal.inrae.fr/hal-02720090

Submitted on 1 Jun 2020

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of

sci-entific research documents, whether they are

pub-lished or not. The documents may come from

teaching and research institutions in France or

abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est

destinée au dépôt et à la diffusion de documents

scientifiques de niveau recherche, publiés ou non,

émanant des établissements d’enseignement et de

recherche français ou étrangers, des laboratoires

publics ou privés.

Assimilate allocation and carbon reserves in Juglans

regia L. seedlings

André Lacointe, . Inra, . Universite

To cite this version:

André Lacointe, . Inra, . Universite. Assimilate allocation and carbon reserves in Juglans regia

L. seedlings. Annales des sciences forestières, INRA/EDP Sciences, 1989, 46 (suppl.), pp.832s-836s.

�hal-02720090�

Assimilate allocation and carbon

reserves

in

_{Juglans regia}

L.

_seedlings

A.

Lacointe

Station de

_{Bioclimatologie,}

INRA, Domaine-de-Crouelle, F-63039 Clermont-Ferrand, France

Introduction

This

_study

was undertaken to answer 3

questions,

some of which have been debated

_by

several

authors,

e.g., Hansen

(1967)

and Kandiah

₍₁₉₇₉₎

on

_apple

trees

or Petrov and Manolov

(1973)

on

_peach

trees. Can a

_growing

_organ

simultaneous-ly

be active as a

_storage

_organ?

Is a

_given

storage

area active at different times? Are the

_dynamics

of reserves different be-tween the stem

_part,

which will bear the

next

_{year’s shoot,}

and the rest of the

stem?

Materials and Methods

Plant material

Walnuts

_{(Juglans regia L.)}

were sown outdoors, on 5 June 1986, in individual _{pots provided} with

an automatic

_irrigation

_system. Germination

occurred around June 20th. The stem

elonga-tion was

_{initially quite}

fast until

_{early July,}

build-ing

up the ’lower stem’ with scaly leaves, then much _slower,

_building

_{up the ’upper} stem’ with true leaves.

!4C

_feeding

On

_August

1st

_{(late primary growth; only}

a few short internodes were still

_being

built: Fig. 1 ), 72

plants were selected for

_homogeneity

and fed for 5 h with

14

C0

2

using

a

_large

assimilation

chamber; 24 _planis at a time received a total of 18.5 MBq (500 uCi). Another set of 72 plants

were fed on October 8th

_(primary

_growth had

stopped

in late

_August).

2-3 plants were

sam-pled

the

day

after

_feeding

and 3 d later, then 8-9

_monthly

until bud-break

(late May).

They were divided into 5

_perennial

_organs

_(Fig.

_1),

plus leaves when _present, frozen in

_liquid

nitro-gen, freeze-dried and

weighed.

The 14C distribution was

_analyzed

qualitative-ly by autoradiography and _{quantitatively} with an

argon-methane

flow counter after

_{dry-grinding.}

Results

Autoradiographs!

(schematic

drawings,

Fig. 2)

The

_taproot

In both

_experiments,

the

_labeling

_pattern

was stable after 3

_days

and remained

unchanged

until bud-break. In the

_August

experiment,

unlabeled wood was pro-duced from the c:ambial zone, from current

assimilates in late summer. The October

labeling,

however,

showed that _wood

pro-duction had

_{stopped by}

that

time,

since no

and the central

_{parenchyma (the}

predomi-nant

_tissues)

were rather

_uniformly

labeled

in both

_experiments.

The upper stem

Although

it was not

_quite

clear before

early

September

in the

_August

_experiment

because of the

_high

amount of

!4C,

the

labeling

patterns

seemed stable after a

few

days

here too.

_They

were,

however,

quite

different between both

_experiments.

In

_August,

most of the !4C

_incorporated

into the

wood,

whereas

_pith

and cortex were

_poorly

labeled. But this is true

only

of the lower

part

of the upper stem. In the

apical

part,

the

_primary

tissues were

strongly

labeled, whereas no !4C could be

detected in the wood

_{(autoradiographs}

performed

from

_{September on):}

the wood

was

_produced

after !4C treatment, from

current unlabeled assimilates. This

proba-bly

reflects the

_growth

_pattern.

However,

the

_boundary

between lower and

_apical

parts

was

_always

situated at a node:

whether this

_{’step’-functioning}

of the

cam-bium was a result of a

_particular

_pattern

of

primary growth

or not is not clear

_yet.

In contrast, the distribution

_pattern

of 14

C concentration after the October

la-beling

was

_{quite simple:}

none in the

wood,

little in the cortex, a little more in the

_pith

and a lot in the buds and the abscission zones which were active at that time.

Quantitative allocation of 14C _among organs

In both

_experiments,

the total

_{radioactivity}

recovered in the

_perennial

_parts

was ca

200

_{kBq (6 pCi)}

_per

_plant.

The leaves retained up to fall ca 100

_kBq

_(August

labeling)

or ca 40

_kBq

_{(October labeling).}

The

_general

_pattern

of distribution among organs

(data

not

_shown)

was

stable after 3 d and remained constant for the duration of the

_experiments.

Most of the

_exported

’14C was recovered in the

taproot

in both

_experiments.

_However,

much more !4G was found in the

_taproot

after the October

_{labeling (80%)}

than after

the

_{August labeling (55%).}

This difference

was also visible in the

plots

of the

specific

radioactivities

_{(SR) (Fig. 3).}

_Moreover,

the SR of the upper stem was

_{significantly}

higher

than that of the lower stem in the October

_experiment,

whereas

_they

were similar in the

_{August experiment.}

There were,

however,

some

_slight

varia-tions with time

_(Aug.

_{exp., Table}

_I).

In

autumn, the

_newly

accumulated

_dry

matter

was labeled less than that

_already

in

_place

(compare

DMW and

_SR).

There was

apparently,

however,

some

_{radioactivity}

still

_circulating

within the

_plant,

since the

total

_{radioactivity}

of the _upper stem

in-creased

_slightly,

but

_{significantly.}

The upper stem was a

_stronger

sink than the lower stem

_(cf.

their DMW

_ratio).

In

winter,

there was a

_slight

decrease in the DMW of

SR: the

_disappearing

DM was

_mostly

made of unlabeled late reserves.

How-ever, as can be derived from the lower

stem

TR,

some

_slightly

labeled material

was also lost. The lower stem was

de-pleted

faster than the upper stem.

Discussion and Conclusion

Similar to the

_findings

of Hansen

₍₁₉₆₇₎

and Kandiah

₍₁₉₇₉₎

on

_apple,

and of

others on other

_species,

the

_export

of assimilates in walnut was directed more

downwards in autumn than in summer.

This was

_apparently

related to the

chang-ing growth

pattern

of the aerial

_part,

whereas the

_taproot

_appeared

to function

as a

_{reserve-accumulating}

organ after either the

_August

or October

_feeding,

whether it was

_undergoing

cambial

_growth

or not.

Moreover,

the whole of the

_storage

area,

namely

the central

_parenchyma,

appeared

to be active at all times.

In

winter,

the different

_depletion

rates between the 2

_parts

of the stem was

per-haps

an indication of a transfer of

reserve-derived nutrients from the lower to the upper

part,

where the

preparation

of bud-break

_probably

resulted in a

_higher

meta-bolic

_activity.

References

Hansen P.

₍₁₉₆₇₎

!4C-studies on

_apple

trees. Ill. The influence of season on _storage and

mobilization of labelled

_{compounds. Physiol.}

Plant 20, 1103-1111 l

Kandiah S.

₍₁₉₇₉₎

Turnover of

_{carbohydrates}

in relation to

_growth

in

_apple

trees. II. Distribution

of !4C assimilates labelled in autumn,

spring

and summer. Ann. Bot. 44, 185-i95

Petrov A.A. & Manolov P. (1973) Autumn

accu-mulation of reserve !4C-labelled assimilates and their

spring

mobilization in _young

_peach

trees. C.R. Acacl.

_Agric.

G. Dimitrov6, 91-102