Leaf Elongation Rate of Mediterranean and Temperate Tall Fescue Cultivars under Water Deficit

The leaf elongation rate of a temperate (Festuca arundinacea Schreb.) and a Mediterranean (F. arundinacea var. letourneuxiana) tall fescue cultivar in response to water deficit was studied in a glasshouse experiment. Plants of both cultivars were grown in the same containers and received water daily with gradation in intensity of water deficit achieved by varying the daily water ration per container. Leaf elongation rate (LER) was calculated for eight successive subperiods during the application of the water treatments. Under the high temperatures registered in this experiment, the Mediterranean cultivar showed lower LERs and tended to be less affected by a moderate water deficit but more affected by a severe water deficit than the temperate one

State of Knowledge in Tiller Dynamics

Persistence of sown pastures is a concern for pastoral production worldwide. Fundamentally, when a pasture does not persist the problem can be expressed in terms of inadequate new tiller production or excessive tiller death. However, the collection of data to build an understanding of sward dynamics at this level is time consuming. Tiller survival diagrams are presented for a range of temperate and tropical grass species including Lolium perenne, Lolium multiflorum, Festuca arundinacea, Festuca pratensis, Phleum pratense, Bromus willdenowii, Cynodon dactylon, Brachiaria brizantha, Panicum maximum, Chloris gayana and Paspalum notatum. It is shown that each grass has a unique perennation strategy and accordingly unique strengths and weaknesses that confer persistence or lack of persistence in different situations. There is also confusion in extension circles about the trade-off between tiller size and tiller density and how to detect a suboptimal tiller density. Grass swards respond to high herbage mass by increase of tiller size and reduction in tiller density, but reduction in tiller density is often mistaken for sward decline. A distinctionmust be made between size/density compensation and sward decline. Increased understanding of sward dynamics at this level should help in the evolution of management practices that improve persistence on a range of grassland types

The reduced leaf expansion of phosphorus deficient maize leaves is associated to a lower cell production

International audienc

The reduced leaf expansion of phosphorus deficient maize leaves is associated to a lower cell production

International audienc

Analysis of the response of tall fescue cultivars of different origin to P deficiency

International audienc

Analysis of the response of two tall fescue cultivars of different origin to P deficiency

International audienceSoil phosphorus (P) availability commonly limits crop growth and forage production. Furthermore, there is a concern about the use of fertilizers, both because of the risk of environmental degradation and P being a non-renewable resource. Some experimental evidence would indicate that certain cultivars of tall fescue of Mediterranean origin would have a higher root:shoot ratio than temperate ones. This characteristic could improve P efficiency. Since P fertilization is a crucial issue in forage production, enabling grass crops to use the soil resources more efficiently represents an important agronomical goal. The objective of the present work was to compare the response of two tall fescues of different origin to low P availability and to analyze the interactions between morphological traits, P uptake efficiency and P use efficiency. Two cultivars of tall fescue (Schedonorus phoenix (Scop.) Holub (formerly Festuca arundinacea (Schreb.)), one of temperate origin, Palenque Plus INTA (PP), and the other of Mediterranean origin, Fraydo (F), subjected to three different P treatments (P1, P2 and P3 obtained by adding 0; 10 or 100 mg P kg(-1) soil-sand mixture 1:1 by weight) were studied in a glasshouse experiment. Four destructive harvests were performed from 24 to 54 days after emergence (dae) and the following determinations were performed: root and shoot components dry matter (DM), leaf area, tiller production, root length and diameter, root and shoot components P concentration. Tissue turnover measurements were performed from 19 to 53 dae. In general, responses to low P availability were in agreement with the literature (e.g. low DM accumulation, higher root:shoot ratio, low leaf elongation rate, low tiller production). Conversely to what was expected, PP had a higher root:shoot ratio than F under low P availability and tended to show higher values of P uptake during the whole experimental period. However, the P uptake efficiency per unit of root length was higher in F than in PP. By the end of the experimental period PP accumulated a higher amount of total biomass than F under P2 and P3. Under moderate P deficiency (P2), shoot growth was less reduced in PP than in F. Under the experimental conditions of the present study PP showed a higher growth potential and a more plastic response to P availability. Experiments at lower temperatures that would favor Mediterranean cultivars growth should be performed to study possible effects of P-temperature interactions on these cultivars

Analysis of the response of tall fescue cultivars of different origin to P deficiency

International audienc

Adaptation of tall wheatgrass to low-P soil conditions is associated to phenotypic plasticity

International audienc

Adaptation of tall wheatgrass to low-P soil conditions is associated to phenotypic plasticity

International audienc