6533b825fe1ef96bd12824ec

RESEARCH PRODUCT

Effects of seed traits on weed seedbank dynamics in response to seed depth and soil structure

subject

description

International audience; Weed seedling establishment in fields strongly depends of soil tillage because it determines both seed depth and soil structure. Species can differ in their ability to develop after germination a shoot able to grow towards the soil surface. The length of the pre-emergent shoot growth is limited and seed size could be a key functional trait related to the maximum shoot growth. Besides, during pre-emergent growth, a proportion of seedlings can remain blocked under obstacles into the soil. This mortality could be linked to the hypo- or epicotyl morphology. This trait could be correlated to the emergence force exerted at the extremity of the shoot in the soil. The maximal length of the pre-emergent shoot and the effects of soil structure through the shoot probability to be blocked under different sizes of clods were studied in controlled conditions for 11 contrasted species. A strong relation (maximal shoot length = 67.5 x seed weight 0.48; r² = 0.85) was observed between seed mass and maximal shoot length. Shoot elongation in the soil occurs without light and is therefore directly dependent on the seed characteristics such as embryo size or the amount of reserves which are more or less positively correlated to seed weight. For each species, the probability of a shoot to be blocked was linked to clod size; the parameters of this relation, i.e. the response to soil structure could then be related to the hypo- or epicotyl diameter. The relationships between seed traits and emergence processes make it possible to predict more easily the behaviour of any species. These data, completed by seed survival in soil, dormancy and germination will be introduced into a plurispecific model in order to predict weed seedbank dynamics and their interactions with agricultural practices.