DI MARCO, O.N. 1; HARKES, H. 2; AGNUSDEI, M.G. 3
The effect of leaf age and length on leaf blade quality was studied in tall wheatgrass (Thinopyrum ponticum
cv. Hulk) leaf blades leaves from swards of two heights. Swards were grown in plots in a greenhouse (17± 4
ºC) in a randomized block design (n=3) of 160 plots/block. Leaves in 6 ontogenic stages from 3 consecutive
leaf generations (from early growth to advanced senescence) were obtained from vegetative tillers (~200/
harvest) harvested along 52 days of regrowth, with a frequency 80 GDD (growing degree days: Σ t1/2- 4,5 ºC).
The leaf lifespan (LLS), leaf appearance interval (LAI), leaf and sheath lengths, NDF content and NDF digestibility
(NDFD) were measured. The relationships among quality and morphogenic parameters were studied by
linear regression and was data analyzed as a complete randomized block design with factorial arrangement (2
heights x 3 leaf generations) and means compared by Tukey test (5%). The shorter leaf sward (241.8 vs 458.4
mm) had longer LLS (453.6 vs 337.8 GGD), similar NDF content and higher NDFD (~10%). In both swards the
NDFD decreased linearly with leaf age and length, but NDF remained unchanged during the LLS. It is concluded
that the NDFD declines with leaf age and length during regrowth, however shorter sward height delays
senescence (>LLS), increases tiller leaving leaf number and improves leaf blade quality.
Keywords: growth, NDF content, NDF digestibility, leaf age, leaf length.