STRESUL HIDRIC LA PLANTE Prezentare realizata in cadrul

STRESUL HIDRIC LA PLANTE Prezentare realizata in cadrul proiectului POS CCE A 2 -O 2. 1. 2 -2009 -2 ID. 524, cod SMIS-CSMR 11986 CERCETARI PRIVIND SEMNIFICATIA RELATIEI DINTRE RASPUNSUL GENOMIC, METABOLISMUL FENOLPROPANILOR SI FOTOSINTEZA IN CONDITII DE STRES ABIOTIC PENTRU OPTIMIZAREA POTENTIALULUI BIOSINTETIC LA SOIURI DE ZMEUR SI MUR

(Lawlor, 2002) Raspunsul plantelor la factorul de stress Ozone Recunoasterea stresului Temperaturi extreme Transducerea semnalului inundatii seceta Activarea unor procese fiziologice saruri Alterarea metabolismului celular 2

Ce reprezinta stresul hidric Seceta include urmatoarele conditii: Deficit hidric al soplului , este cauzat de lipsa precipitatiilor si lipsa apei disponibile in sol. Deficit hidric al aerului , RH<20% in atmosfera，transpiratia>>absorbtia apei Potentialul hidric al tesuturilor: Pressure Chamber Technique Thermocouple Psychrometer Method Mic: Ψcell ~-0. 5 MPa Moderate: Ψcell ~-0. 5 to -1. 5 MPa Sever: Ψcell ~<-1. 5 MPa Continutul relativ de apa: Mic: ~90% Moderat: 80 -60% Sever: <50% Supraviatuire Ψcell of -11. 5 MPa Activitate fotosintetica – 5. 0 to -8. 0 MPa Creosote Bush: Larrea tridentata

Adaptare vs. Aclimatizare Saguaro Stress abiotic aclimatizarea Mojave desert star Rezistenta - evitare - toleranta Mojave desert star Impatiens capensis 4

Modificari ale frunzelor SLA (specific leaf area) Suprafata foliara/ substanta uscata Desertice (xeric): 0. 02 - 0. 12 Paduri uscate: 0. 36 - 0. 70 Mezofite: 1. 4 -1. 6 Dissected leaves in Palo Verde

Scaderea suprafetei foliare GR - growth rate ΨP – turgor Y - yield threshold (the pressure below which the cell wall resists nonreversible deformation) m - wall extensibility (the responsiveness of the wall to pressure) 6

Sistemul radicular –crestrea ratei racina/lastari Raporta sistem radicular/parte aeriana: Paduri temparate: ~0. 25 savana ~0. 3 – 0. 4 desert~0. 6 -0. 9 Micoriza creste volumul radicular

of growth Deficitul hidric intensifica cresterea radacinilor Tipul salbatic si mutante ABA-deficient de porumb cultivate in conditii normale si deficitare de apa 8

Deficitul hidric provoaca abscizia frunzelor Leaves of young cotton plants abscise in response to water stress 9

… inchiderea stomatelor mediata de ABA c. ADPR – cyclic ADP-ribose ROS – reactive oxygen species R – Receptor IP 3 – inositol triphosphate NO – Nitric oxide PA – Phosphopatidic acid PLC – phospholipase D S 1 P – Spingosine-1 Phosphate PLC – phospholipase C 10

Deficitul hidric scade rata fotosintezei Efectul deficitului hidric asupra cresterii frunzelor si a ratei fotsintezei la floarea soarelui 11

Water stress affects translocation of nutrients Relative effects of water stress on photosynthesis and translocation in sorghum Plants exposed to 14 CO 2 for a short time interval. Radioactivity fixed in the leaf taken as a measure of photosynthesis, and loss of radioactivity after removal of 14 CO 2 taken as a 12 measure of rate of assimilate translocation.

A =gs ( Ca-Ci) A =gm (Ci-Cc)

How does drought cause the generation of ROS? 14

How does drought cause the generation of ROS? O 2 • O 2– 3 P 680* 3 O 2 SOD H 2 O 2 SOD – Superoxide Dismutase 1 O * 2 15

Fates of sunlight absorbed in the lightharvesting chlorophyll complexes Chl – chlorophyll 1 Chl* – excited singlet chlorophyll 3 Chl* – excited triplet chlorophyll Demmig-Adams & Adams III 2000 Nature 403: 371 P – photochemistry (green) D – safe dissipation of excess excitation energy as heat (red) F – fluorescence 3 T – triplet pathway, leading to the formation of singlet oxygen (1 O 2*) and photo-oxidative damage 16

Actiunea ROS asupra celulelor 17

3. Scavenging ROS � Enzymes： 1) SOD（superoxide dismutase) 2) POD (Ascorbat. Peroxidase) 3) CAT (Catalase) � Oxidants： 1) 2) 3) 4) 5) carotene Vit E Vit C GSH phenolics