INFLUENCE OF INCIDENT IRRADIANCE ON THE GROWTH OF PATAGONIAN CYPRESS SEEDLINGS IN NURSERY

MASSONE, DIEGO; PASTORINO, MARIO; TAMBUSSI EDUARDO ALBERTO; BARTOLI CARLOS GUILLERMO

Santa Fé

Congreso; XXXIII Argentinian meeting of Plant Physiology; 2021

Sociedad Argentina de Fisiología Vegetal

Patagoniancypress (Austrocedruschilensis (D. Don)Pic.Serm.etBizzarri) is a native conifer of the sub-antarcticforest, whichis considered an isohydricspecies with a strong stomatal control. Thischaracteristic might be the cause of the low rate of its initial growth, evenin the nursery under optimal conditions of irrigation, fertilization andtemperature control. Seeking to understand the effect of irradiance on thisbehavior, the objective of this work was to determine how different shadingdynamics through gaps, stripsor diffuse lighttreatments influencethe development of Patagonian cypress seedlings in the nursery. We worked undertwo specific hypotheses: (1) High levels of irradiance cause damage ofphotosystems producing an inhibition of photosynthetic activity; (2) Highlevels of irradiance decrease photosynthesis indirectly through stomataclosure. Patagonian cypress seedlings, were grown at three shading dynamics(gaps, striped, and diffuse) and contrasted with full incident light,evaluating the effect of these treatments on morphological variables andallometric relationships. Higher growth was observed in plants under the gapsand the strips irradiance treatments,maintaining good allometric relationshipsin both cases. In addition, photosynthesis was analyzed through the measurementof modulated fluorescence of chlorophyll and photosynthetic oxygen evolution ina CO2saturated atmosphere. No differences were observed in thiscomplementary analysis, suggesting that the light environment does not restrictplant growth through increasedphotoinhibition or decreasedpotentialphotosynthesis. To further test the stomatal limitation induced by lighttreatments, the measurement of13C concentration in leaf tissues isnow in progress.