BELOWGROUND HORMONAL INTERACTIONS IN PLANTS & OZONE

Transcription

1 BELOWGROUND HORMONAL Slovenian Forestry Institute INTERACTIONS IN PLANTS & OZONE CRISTINA CRUZ 1, MARTA DELGADO, PEDRO ANTUNES, M.A. MARTINS-LOUÇÃO & HOJKA KRAIGHER 2 1 PLANT BIOLOGY, UNIVERSITY OF LISBON, PORTUGAL 2 SLOVENIAN FORESTRY INSTITUTE, VEČNA POT 2, 1000 LJUBLJANA, SLOVENIA

2 Plant growth substances are essential factors for plant development and are important signals for the interaction between plants and microbes.

3 ROOT AND MYCORRHIZA Mycorrhiza formation and root architecture result from a permanent tuning between resource allocation and the production of growth substances by the plant and the microorganisms. Check Republic,14-16 June 2011, Cruz et al

4 REGULATION IN MYCORRHIZA MINERAL HYPOTHESIS (Stahl, 1900) CARBOHYDRATE HYPOTHESIS (Björkman, 1970) HORMONAL HYPOTHESIS (Slankis, 1973) COMPLEX HYPOTHESIS (Gogala, 1991) HORMONES (CH 2 O)n MINERALS

5 CHARACTERISTICS OF DIFFERENT FORMS OF MYCORRHIZA ARBUSCULAR MYCORRHIZA ARUM TYPE PARIS TYPE ECTOMYCORRHIZA ECTENDOMYCORRHIZA ERICOID MYCORRHIZA ARBUTOID MYCORRHIZA ORCHIDACEOUS MYCORRHIZA MONOTROPOID MYCORRHIZA Peterson 2006

6 ROOT TO SHOOT TO ROOT SIGNALLING (OTHER THAN WATER & NUTRIENTS) Move acropetally & influence physiological processes in target organs, which are remote from putative synthesis organs Concentrations in roots, xylem sap (& recycling from phloem) & leaves ABA, auxins, cytokinins, ethylene, gibberellins etc cross-talk & pre-set condition specificity; act as master-signals masking over other PGR also produced in the rhizosphere by mycorrhizal fungi, PGPR, N-fixing bacteria etc.

7 CYTOKININ (CK) STUDIES 150,00 100,00 ip 50,00 Z DZ Fraction numbe r ,00 9,00 8,00 7,00 6,00 5,00 4,00 ip 3,00 2,00 Z 1,00 0, DZ Fraction number Cytokinin-riboside equivalents (pmol/ml) In N. spruce pollution accelerated scenescence symptoms were associated with elevated CK (Von Schwartzenberg & Hahn 1991, Kraigher & Hanke 1995 & 1996, Dent & Hanke 1995) A number of ECM fungi were found to produce CK (Miller 1968, Gogala 1971, Kraigher & al 1991) Colonization of Ns with two strains of Thelephora terrestris (UK & SI) affected CK content differently (Kraigher & al 1993) Cytokinin-riboside equivalents (pmol/ml) 200,00

8 CYTOKININS IN BEECH (WINWOOD ET AL. 2007) CYTOKININS Isoprenoid (ip & Z) and aromatic CK were detected in leaves L (equal conc!), roots R, xylem X and phloem P (ip) Inactive O-glucosides were dominant in scenescing L; no effect on CK contents by 2xO 3 In 2xO 3 R conc 2-3x higher than in 1xO 3 R & X In 2xO 3 L conc 2-3x lower than in 1xO 3 L & P CK-L: O 3 induced CK destruction signalling to R CK-P: O 3 induced increase in root & ECM development, which in turn induces higher CK-R & CK-X Increased cytokinin content of roots & xylem in 2xO 3 in accord with increased synthesis from root growth and ECM Drawing by D.E.Hanke (

9 CYTOKININS Rhizopogon ochraceorubens Several mycorrhizal fungi are able to produce and excrete cytokinins (trans-zeatin and trans-ribosylzeatin. Gogala 1971) to the medium - Crafts and Miller (1974) Among them - Rhizopogon ochraceorubens - Suillus punctipes, - Boletus edulis var. pinicolus Regarding to the effects of cytokinins on fungi, they have shown to influence the content of K, Ca, P and Na in the mycelium of Suillus variegates (Pohleven & Gogala, 1986). Increased fluidity of hyphal membranes (Pohleven et al 1999). The majority of the studies report that at later phases of mycorrhization, cytokinin levels increase in plant roots and shoots (Allen et al., 1980, van Rhijn et al., 1997). This increase can be due to increased phosphate nutrition in mycorrhizae, resulting in cytokinin production (Barker & Tagu, 2000) Suillus punctipes

10 AUXINS Auxins play an important role in root growth, tropism, apical dominance, plant senescence cell expansion, cell division, and cell differentiation (Davies 2004). Mycorrhizal root tips Root nodules In particular, auxins profoundly influence root morphology by inhibiting root elongation, increasing lateral root production, and inducing adventitious roots (Fukaki et al. 2007; Ludwig-Müller et al. 2005; Rahman et al. 2007). Mycorrhizal roots exhibit morphological characteristics like increased number of lateral roots during growth phase, similar to those found in plants treated with auxins (Ludwig-Müller, 2000).

11 AUXINS Auxin application in plants revealed an increase in mycorrhization rates (Müller, 1999). Hebeloma hiemale Measurements of endogenous contents of free and conjugated auxins increased the support on this theory. Gay (1986) reported that the fungus Hebeloma hiemale can induce rhizogenic effects in Pinus halepensis, detecting IAA production in an isolated culture. In Glicine max, mycorrhizal roots were also associated with elevated IAA free-content (Meixner et al., 2005).

12 IS RHIZOSPHERE FUNCTION AND STRUCTURE AFFECTED BY THE ATMOSPHERIC OZONE CONCENTRATION? Ecosystem manipulating experiment N addition

13 BIODIVERSITY AT ARRÁBIDA

14 IN THE FIELD. Matorral 7 ppm P Cistus ladanifer

15 IN THE FIELD. Cistus ladanifer 66 types 512 OTU

16 IN THE FIELD. IAA in the root tips (M) C 20N 40N 80N Number of types Cistus ladanifer 72 Types 515 OTU 0 C 20N 40N 80N Fuentes et al 2011

17 IN POTS. Air with ambient O 3 concentration (control) Plant Plant Plant Plant Air plus 12 h O 3 concentration of 2 times ambient Litter Bulk Litter Bulk Litter Bulk Litter Bulk Plants and soil were collected at N control and 80 N plots The experiment last for 45 days (Phytotron) C 80 kg N ha -1 year -1

18 IN POTS

19 IN POTS

20 PLFA PROFILE. From pot soils with plants (Cistus ladanifer)without N addition A consistent tendency for a decrease in the amount of actinomycetes was observed 16:0 (10Me) 17:0 (10Me) 18:0 (10Me)

21 IN THE POTS. Increased O 3 lead to more formation of endomycorrhiza in Cistus ladanifer and to a decrease in IAA concentration in the root tips This may be the result of change in the EM population and/or other rhizosphereic microorganisms. Ex: Actinomycetes tend to increase IAA concentration in the root tips and it seems that their concentration tend to decrease with O 3

22 OZONE EFFECTS ON SOIL RHIZOSPHRE ARE MEDIATED BY PLANTS < S to R C flow Qualitative data: changes (More important in young plants) N/P C Aux Cyt SGL Aux SGL Aux SGL Oxylipins SGL SGL Aux in ECM community structure were ctd. reported. Variability due to species & age of plants, length of stress & experimental conditions. It is therefore often impossible to scale up results from experiments under controlled conditions to the forest scale. (Cudlin & al 2007 part of COST E38)

23 Overall O 3 impacts: young adult forest tree ADULT Longlived, well established forest trees Relatively unsensitive Reduced C assimilation & repair C-costs less pronounced at a whole tree level YOUNG Sensitive to stress Reduced C assimilation Induction of repair mechanisms at C cost Ambiental O 3 Elevated O 3 ACKNOWLEDGEMETS Ambiental O 3 Change in hormonal up&down regulation Transient? higher fine root production & turnover Transient? change in ECM community structure Impacts on C sequestration in fine roots & ECM Elevated O 3 Less carbon: roots starved, change in ECM community, lower fine root production Impacts on stability and sustainability of forest regeneration centers & ecosystem functioning Kraigher, Grebenc & Hanke: Ozone stress and ectomycorrhizal root-shoot signalling (2008)

24 OZONE EFFECTS ON SOIL RHIZOSPHRE ARE MEDIATED BY PLANTS < S to R C flow Qualitative data: changes (More important in young plants) N/P C Aux Cyt SGL Aux SGL Aux SGL Oxylipins SGL SGL Aux in ECM community structure were ctd. reported. Variability due to species & age of plants, length of stress & experimental conditions. It is therefore often impossible to scale up results from experiments under controlled conditions to the forest scale. (Cudlin & al 2007 part of COST E38)

25 BELOWGROUND HORMONAL INTERACTIONS IN PLANTS & OZONE Financial support FCT Thank you