Comparaison des dynamiques d'apparition et de mortalité des organes de fétuque élevée, dactyle et luzerne (feuilles, talles et tiges)

Abstract

phyllochrone / indice foliaire / talle / tige / lumière Summary — Comparison of organ appearance and senescence rates in tall fescue, cocksfoot and lucerne (leaves, tillers and stems). Three forage species (tall fescue, cocksfoot, lucerne) were cultivated without nitrogen and water stress. Rates of leaf appearance and senescence were compared for several regrowths (1 in spring and 2 in summer for grasses, 3 in summer and 1 in autumn for lucerne). We showed that the average phyllochrones were 83 degree-days for lucerne, 188 for cocksfoot and 253 for tall fescue and were dependent on regrowth, and always increased during regrowth. These intraspecific variations were interpreted respectively by an increase in competition for light during a given regrowth and by differences in temperature according to regrowth. The maximum number of completely green leaves per tiller or stem was a characteristic of a species (from 9 to 11 for lucerne, 3 to 4 for cocksfoot, 2 to 3 for tall fescue). However, the degree-days from leaf appearance and the beginning of senescence were less variable than those for phyllochrone (452 for cocksfoot, 516 for tall fescue and 705 for lucerne).For regrowths with no nitrogen and water limitations, tiller or stem density did not increase after defoliation so that the increase in leaf index only resulted from leaf appearance and elongation rate.These results were used to discuss the choice of a partner to associate with lucerne. For grasses, we concluded that once the maximal number of green leaves was reached, there would be an increase in lamina weight only if a lamina of given length was replaced by a longer lamina. In case of partial defoliation, the time needed to attain the maximal number of leaves could be shorter, and the amount of senescent material greater.

Calibration of the APSIM-Lucerne model for ‘Grasslands Kaituna’ lucerne crops grown in New Zealand

“…use of different base temperatures). However, values of up to 80°Cd were reported for cultivars, for example, 'Magali' in France (Duru et al 1993). This suggests that phyllochron needs to be considered at the cultivar level rather than the species level when parameterising the lucerne model.…”

A Model of Lamina Digestibility of Orchardgrass as Influenced by Nitrogen and Defoliation

“…We used daily temperature, averaged over a period preceding the sample date. This period was equal to three phyllochrons (i.e., 150 degree‐days × 3; Duru et al, 1999a), when considering the overall green lamina on a tiller, assuming that there are three green mature laminae on an orchardgrass tiller (Duru et al, 1993).…”

Herbage volume per animal: A tool for rotational grazing management

“…The negative relationship with the residual herbage mass could have 2 causes. First, the length of leaves which become senescent is directly proportional to the residual herbage mass through their lifespan (Davies 1988), which is usually rather constant for a given species when expressed in degree-days (Duru et al 1993). Second, part of the respiration depends on plant mass, about 1.5% per day (Parsons 1988).…”