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RESEARCH PRODUCT

What are the biological determinants of regeneration of perennial weeds? Effect of fragment weight and bud number on the regrowth of five perennial weed species

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Perennial weeds have become an increasing problem with the reduction of herbicide use andtillage. Because of their capacity to regenerate from vegetative organs, such as roots andrhizomes, they must be controlled with different management techniques than annuals. Todate, few studies exist on this topic and farmers often lack solutions to control perennials intheir cropping systems. Management strategies must focus on the depletion of theregenerative organ reserves to hamper the production of new shoots. However, there is aneed for a better understanding of below-ground organs physiology and the determiningfactors of their regrowth capacities.Our aim was to assess the number of shoots and their growth speed from one below-groundfragment according to 1) its weight, which is related to the amount of available reserves, and2) the number of buds initially present (visible) on it. Five species were investigated:Cirsium arvense, Sonchus arvensis, Convolvulus arvensis, Elymus repens and Rumex crispus.They were chosen for their frequency and harmfulness in arable crops in temperate regionsand for their difference in terms of multiplication strategy, which implies different vegetativeorgans. Two pot experiments were carried out in a greenhouse: fragments of roots andrhizomes with different weights or different visible bud numbers were buried into 6-L pots,and the number and length of the produced shoots were measured dynamically during theexperiment. The effects of fragment nature (creeping root, rhizome, taproot), weight and thenumber of buds on (1) the probability that a fragment produce a shoot, (2) shoot growth rate,(3) shoot number and (4) maximum shoot length were analyzed. Also, shoot length wasQuantified as a function of hydrothermal time since bud sprouting.These results will be used to model regrowth of perennials from below-ground fragmentsafter tillage in a cropping system simulation model (FLORSYS). This model simulates daily weeddynamics and crop production over the years from cropping system and pedoclimate. Theultimate goal will be to identify agroecological weed management strategies and to helpfarmers to redesign their cropping systems.