Light energy management in peach: utilization, photoprotection , photodamage and recovery. Maximizing light absorption in orchard is not always the best solution

摘要: The relation between the intercepted light and orchard productivity was considered linear, although this dependence seems to be more subordinate planting system rather than intensity. At whole plant level not always increase of irradiance determines improvement. One reasons can intrinsic un-efficiency in using energy. Generally full only 5 – 10% total incoming energy is allocated net photosynthesis. Therefore preserving or improving efficiency becomes pivotal for scientist fruit growers. Even tough a conspicuous amount reflected transmitted, plants avoid absorb photons excess. chlorophyll over-excitation promotes reactive species production increasing photoinhibition risks. dangerous consequences forced evolve complex multilevel machine able dissipate excess quenching heat (Non Photochemical Quenching), moving electrons (water-water cycle , cyclic transport around PSI, glutathione-ascorbate photorespiration) scavenging generated species. price must pay equipment use CO2 reducing power with consequent decrease photosynthetic efficiency, both because some are used carboxylation an effective loss occurs. Net photosynthesis increases until saturation point, additional PPFD doesn’t improve but it rises alternative pathways dissipation also ROS risks. The wide photo-protective apparatus, cope excessive energy, therefore photodamage occurs. Each event photon pressure and/or decreasing described mechanisms (i.e. thermal stress, water nutritional deficiency) emphasize photoinhibition. Likely nature small damaged photosystems found effective, efficient consuming recovery system. Since PSII quickly repaired expense, would interesting investigate how much costs productivity. This PhD. dissertation purposes knowledge about several strategies accomplished managing implication on photo-damage peach. thesis organized three scientific units. In first section new rapid, non-intrusive, tissue universal technique functional determination implemented validated different kinds as C3 C4 species, woody herbaceous plants, wild type Chlorophyll b-less mutant monocot dicot plants. second unit, “singular” experimental named “Asymmetric orchard”, environment performance, investigated peach at level, furthermore effect variation management single leaf. third analysis method suggested by Kornyeyev Hendrickson (2007) validate Afterwards applied field where influence moderate reduction performances, requirements, studied. Using solar fuel life intrinsically suicidal since high constant risk. This try highlight existing plant, particular peach, analysing principal developed manage deriving maximal benefits possible minimizing risks. In instance proposed based P700 redox kinetics valid, non intrusive, field-applicable technique, even measure deep leaf layers fluorescence. Fluorescence Fv/Fm parameter gives good estimate when data obtained ad-axial ab-axial surface averaged. addition (2007), combined model von Caemmerer (2000) forceful tool analyse study, field, environmental factors such water, temperature all light. “Asymmetric” training way study performance relations field. reaching saturating point. Light may stress leading stomatal limitation. Furthermore too does promote improvement damage, fact most exposed 50-60% inactivated. till point (1000 1200 μmolm-2s-1) dissipated photochemical carboxylative transports. latter follows quite similar pattern Pn/PPFD curve almost same flux density. middle-low NPQ lumen pH limited enough generate optimum violaxanthin de-epoxidase (VDE) activation. Peach leaves light excess While xanthophyll activated rate transports reduced. Some these transports, water-water cycle, PSI H+ order support VDE activation limiting. Moreover involved important dissipative sub-optimal conductance determine but, diminishing evapo-transpiration request, decreases, efficiency. lowering intensity limiting levels, could saved compromising partition absorbed utilization, photoprotection photo-oxidation pathways. When permitted few remained un-repaired, damage recorded placed light. Even experiment, over main pathway quenching; other photorespiration contribute creating optimal trans-thylakoidal ΔpH de-epoxidase. These become very low environment. Another aspect pointed out role severely limiting. The evidence that seen indicates presence mechanism masks real occurring during day. repair allowed two fold photoinhibited shaded ones. the photosynthetic optima damage. The consequently dry matter allocate essential activity. above while terms tree productivity. An importance further widened parameters, like status, nutrition light, phtosyntate management.