Stability of sunflower leaf development in France and Argentina

DOSIO, G.A.A.; LEFEUVRE, T.; SUARD, B.; IZQUIERDO, N.G.; AGUIRREZÁBAL, L.A.N.; TURC, O.

Toulouse, Francia

Conferencia; 15è Conférence Internationale Tournesol; 2000

International Sunflower Association

Leaf area plays a key role in crop biomass accumulation and therefore in yield formation in sunflower. Accurate prediction of the timing of leaf area development is essential to analyse and predict the responses of plants to the environment. According to Granier and Tardieu (1998, 1999), two phases have to be taken into account during leaf development. During the first one, leaf growth is exponential; during the second one, leaf relative expansion rate decreases rapidly to reach zero at the end of leaf expansion. The objective of this work was to build a model to predict the dates of the two phases for all the leaves of  sunflower plants in a wide range of thermal and radiative conditions. Two hybrids of sunflower were sown at different dates and densities in field and greenhouse experiments at Montpellier (France) and Balcarce (Argentina). The growth of all leaves, including those developing inside the apical bud, was recorded by direct measurement or microscope observation and image analysis. Air and leaf temperature was continuously recorded. On a thermal time scale, the chronology of leaf development was the same for the 2 studied hybrids, for the different locations (France, Argentina, field and greenhouse), for isolated plants or plants in canopy. Only mean daily temperature was necessary to predict the key-dates (primordium initiation, end of exponential growth and full expansion) of development of each leaf. Such a model is a powerful framework both in analysis and prediction of  leaf growth responses to environment.