LEAF SENESCENCE IN SUNFLOWER WAS ADVANCED OR DELAYED DEPENDING ON CHANGES IN THE SOURCE-SINK RATIO DURING THE GRAIN FILLING PERIOD

MARTÍNEZ VERNERI, J.; LORENZO, M.; RIZZALLI, R.; DOSIO, G.A.A.

Edirne

Conferencia; 19th International Sunflower Conference; 2016

International Sunflower Association

Lifespan ofleaves is usually associated to grain yield in sunflower. During the grainfilling period, demand of grains converges with a decreasing green coverage.The source-sink ratio (SSR) allows estimating a carbon budget between theorgans vegetative and reproductive of the plant. The aim of this work was tostudy the effect of the source-sink ratio during the grain filling period onthe leaf senescence in sunflower. Sunflower hybrid VDH 487 was sown in a fieldtrial, and maintained in good conditions of water and nutrition. The SSR wasincreased in three moments (head removal), and decreased in one (shading),during the grain filling period. Senescence was evaluated from the decrease inthe levels of chlorophyll, fluorescence, carbohydrates and dry matter, inleaves 15, 20 and 25 (from the bottom). The progress of all studied variableswas advanced about 175°Cd in leaf 15 in comparison with leaves 20 and 25 (p<0.05). The increase in the SSRdelayed leaf senescence measured trough all variables studied in this work upto 400°Cd, depending on the leaf number and the variable itself. In generalterms, delay was greater when plants were submitted to longest periods of highSSR. Conversely, a decrease in SSR advanced senescence. Depending on the leafand the studied variable, this advancement attained up to 256°Cd (for thedecrease in carbohydrates content). In this work, we verified, by manipulatingSSR, that leaf senescence is not fixe in time. As in most monocarpics, grainfilling played an essential role in senescence.