Recovery of photosynthetic activity in european pedunculate oak provenances after drought

Krunoslav Sever, Saša Bogdan, Željko Škvorc, Ida Katičić Bogdan, Daniel Krstonošić,

Martina Temunović and Jozo Franjić

Faculty of forestry, University of Zagreb

Svetošimunska 25, 10 000 Zagreb

NATURAL RESOURCES, GREEN TECNOLOGY & SUSTAINABLE DEVELOPMENT /3 Zagreb 5th – 8th June 2018

Phenotypic and Epigenetic Response to Drought Stress and Adaptability of Quercus robur L. Populations along a Latitudinal Gradient – Perda Quercus

• Accordingly to Arend et al. (2016) the whole seasonal drought response of net CO2 assimilation (in F. sylvatica) was divided into three distinct phases: • 1. drought limitation from spring to mid-summer • 2. recovery after drought release in mid-summer • 3. post-drought stimulation from late-summer until the end of the vegetation period in autumn

• Drought limitation phase

• Mesic provenance lost 87. 3 μmol CO2 m-2 s-1

• Xeric provenance lost 78.2 μmol CO2 m-2 s-1

• Post-drought stimulation phase • Mesic and xeric provenance got 18. 9 μmol CO2 m-2 s-1

• Recovery • Mesic provenance lost 24 μmol CO2 m-2 s-1 (20 days)

• Xeric provenance lost 14 μmol CO2 m-2 s-1 (10 days)

Introduction

• Arend et al. (2016) press in Agricultural and Forest Meteorology 220: 83 -89

• Efficiency of photosynthetic activity is closely related to the plant water status. • Accordingly, photosynthetic response to drought is a good indicator for assessing the ability of

acclimatization and adaptation of forest trees to long-lasting summer drought as an integral part of global climate changes (Xu et al. 2010; Arend et al. 2012; Speiss et al. 2012; Pflug et al. 2018).

Estonia

Lithuania

Poland

Hungary Croatia

Italy

• 2013 - sowing of collected acorns from 6 european provenances (autumn)

• 2014 - planting of seedlings in 50 L pots (spring) • 2014 - aclimatization of plants in pots • 2015 - begining of measurements (spring)

Aims and hypothesis:

• The main goal of our study was to investigate the capacity of six European pedunculate oak provenances to recover its photosynthetic activity from long-lasting drought.

• Hypothesis was: recovery of net CO2 assimilation in provenances which originated from drier habitats will be more efficient than in provenances that originated from wetter habitats.

CMD

Soil is not wet within 80

cm for over 3 months

during the year

Wet within 80 cm for 3 to 6

months during the year

Wet within 80 cm for over

6 months during the year

138.7

Estonia (ES) Lat: 58.23852; Long: 22.44289

Alt: 7; Rdis: 120.5; HG: 1C

MAT: 6.1; MAP: 568

MDpP: 86; MPDpP: 134

MGSP: 220

156.2

Lithuania (LI) Lat: 54.53797; Long: 23.81117

Alt: 100 m; Rdis: 4.8 km; HG: 3

MAT: 6.4 °C; MAP: 625 mm

MDpP: 157 mm; MPDpP: 143 mm

MGSP: 300 mm

221.7

Poland (PL) Lat: 51.19030; Long: 16.54901

Alt: 118; Rdis: 5.1; HG: 3

MAT: 8.6; MAP: 555

MDpP: 167; MPDpP: 134

PGSP: 301

263.7

Croatia (CR) Lat: 46.13976; Long: 17.09161

Alt: 130; Rdis: 1.4; HG: 2

MAT: 10.8; MAP: 793

MDpP: 225; MPDpP: 154

PGSP: 379

368.1

Hungary (HU) Lat: 47.02512; Long: 18.26349

Alt: 137; Rdis: 48.0; HG: 1L

MAT: 10.8; MAP: 562

MDpP: 169 MPDpP: 112

PGSP: 281

454.0

Italy (IT) Lat: 42.75538; Long: 18.91804

Alt: 137;Rdis: 0.08; HG: 4W

MAT: 14.3; MAP: 723

MDpP: 215; MPDpP: 237

PGSP: 452

Drier habitats Annual dominant soil water regime (WR) Wetter habitats

• Local climate variables was generated with the ClimateEU software (Hamann, A., Wang T., Spittlehouse D.L., Murdock T.Q. 2013; ClimateEU, unpublished software package for Europe freely available at http://www.ualberta.ca/~ahamann/data/climateeu.html).

• The annual average soil water regime and hydro-geological data for the provenance site are combination of data from the Institute for Environment and Sustainability of the European commission Joint Research Center (JRC) and personal field observation. http://eusoils.jrc.ec.europa.eu/ESDB_Archive/ESDB/Index.htm

• Estonia and Hungary - Soil with permeable substratum, remote from groundwater: seldom wet, very far from the river

• Lithuania, Poland and Croatia - Lowland soil affected by groundwater, seasonally or permanently wet

• Italy - Soil of uplands and montins, very wet soil with organic surface horizon, very close to the river

• Local habitat conditions

Control treatment

Drought/re-watering treatment

Control treatment - SWC 38 – 46 %

Drought treatment Re-watering treatment

Ap

ril 0

1st

May

25

th

July

13

th

July

21

st

Au

g 1

7th

July

30

th

July

23

th

Jun

e 1

4th

Sep

t 1

4th

Oct

22

nd

Start of re-watering treatment on 22nd July

Drought limitation period SWC was 15 – 20 %

Post drought stimulation period SWC was 38 – 46 %

• Set up of pot greenhouse experiment • 212 plants (orginated from 6 provenances) separated in 2 main plot treatmants (Control and Drought)

with re-watering as a sub-tretment.

• Control – SWC above 38 % all the time (1st April – 22nd October)

• Drought/rewatering

• Drought – no water at all until visible stress symptoms occur (leaf wilting and/or yellowing), (1st April – 21st July).

• Re-watering – onset after occuring visible stress symptoms (22nd July – 22nd October).

• Measurement traits • SWC (%) – automaticaly weather station • Ψpre dawn (MPa) – water potential in leaves • PN (μmol CO2 m-2 s-1) – net CO2 assimilation • gs (mmol H2O m-2 s-1) – stomatal conductance • ci (μmol CO2 mol-1) – intercellular CO2 • PItot – total performace indeks of PS II

• Gas exchange parameters and pre-dawn leaf water potential was assessed in stressed and non-stressed saplings during the recovery phase.

Results - soil water conditions and tree water balances

• From 1st April to 21st July, SWC in drought treatment gradually decresed.

• At the last day of the drought period, SWC in drought treatment of all provenances was very close to the permanent wilting point (15.0 % of SWC).

• At the end of drought period, mean ψPD in drought treatment of Estonian provenaces (–1.55 ± 1.0 MPa) was significantly higher than in other proveneces. Hungarian (–2.41 ± 1.05 MPa), Italian (–2.49 ± 0.97 MPa) and Lithuanian (–2.55 ± 1.03 MPa) proveneces has a simmilar and significantly higher ψPD than Croatian (–3.18 ± 0.86 MPa) and Poland (–3.38 ± 0.66 MPa) provenances.

• Rewatering treatment resulted in a rapid and complete recovery of SWC and ψPD in stressed saplings of all proveneces to the levels of regularly irrigated control saplings for only one day.

Results - gas exchange parameters

• Different capital letters indicate significant differences (p < 0.05) among provenances within control treatment

• Different lowercase letters indicate significant differences (p < 0.05) among provenances in drought/re-watering treatment.

• * - significant difference between treatments

• Vertical bars indicate ± SE

Control treatment

Drought/rewatering treatment

Results – gs and PN normalised by Ψ and total performace indeks of PS II (PItotal)

Ψ (-MPa) Ψ (-MPa)

• We used total performance indeks of PS II (PItotal) as fluorescence indicator of stress sensitivity. • PItotal is a chlorophyll a fluorescence parameter that integrates light harvesting, electron trapping and energy conversion at PS II.

Conclusions • Only for eight days after the drought release, the photosynthetic activity of all

provenances was fully recovered.

• It confirms absence of significant differences among the provenance in rate of net CO2 assimilation , as well as, absence of significant differences between previously drought treted and control plants in efficiency of PSII, of all provenances.

• Our result confirms the persistence of a very efficient biochemical mechanisms that provides very fast recovery of photosynthetic activity in pedunculate oak after drought release (Epron and Dreyer 1993; Arend et al. 2012; Speiss et al. 2012). Moreover, it is determined in all provenances regardless of the wetness of their original habitat.

• According to the obtained results our hypothesis was not confirmed. • At the peak of the drought stress, photosynthetic activity (gs, Ci, PN and PItotal) in

Estonian provenance whic originated from dry habitat was more efficient than in the other provenences whic originated from wetter habitats (Lithuanian, Poland, Croatian and Italian), including Hungarian provenances which originated from dry habitat like as Estonian.

• This results indicate that Estonian provenance, unlike all others, has a very pronounced mechanism for both, avoidance and tolerance of drought stress.