Abstract
Light interception is a key factor driving the functioning of wheat-pea intercrops. The sharing of light is related to the canopy structure, which results from the architectural parameters of the mixed species. In the present study, we characterized six contrasting pea genotypes and identified architectural parameters whose range of variability leads to various levels of light sharing within virtual wheat-pea mixtures. Virtual plants were derived from magnetic digitizations performed during the growing cycle in a greenhouse experiment. Plant mock-ups were used as inputs of a radiative transfer model in order to estimate light interception in virtual wheat-pea mixtures. The turbid medium approach, extended to well-mixed canopies, was used as a framework for assessing the effects of leaf area index (LAI) and mean leaf inclination on light sharing. THREE GROUPS OF PEA GENOTYPES WERE DISTINGUISHED: (i) early and leafy cultivars, (ii) late semi-leafless cultivars and (iii) low-development semi-leafless cultivars. Within open canopies, light sharing was well described by the turbid medium approach and was therefore determined by the architectural parameters that composed LAI and foliage inclination. When canopy closure started, the turbid medium approach was unable to properly infer light partitioning because of the vertical structure of the canopy. This was related to the architectural parameters that determine the height of pea genotypes. Light capture was therefore affected by the development of leaflets, number of branches and phytomers, as well as internode length. This study provides information on pea architecture and identifies parameters whose variability can be used to drive light sharing within wheat-pea mixtures. These results could be used to build up the architecture of pea ideotypes adapted to multi-specific stands towards light competition.
Highlights
Cereal –legume intercropping systems are assumed to provide high and stabilized yields in terms of quantity and quality (Ofori and Stern 1987; Jensen 1996; CorreHellou et al 2006), allow lower use of fertilizers and pesticides, and enhance biodiversity conservation
Our results show that the pea genotypes exhibited different branching capacities, lateral branches were less developed compared with field-grown spring (Jeudy and Munier-Jolain 2005; Spies et al 2010) and winter cultivars
Our results showed that light sharing was mainly related to the architectural parameters that composed the leaf area index (LAI) and leaf inclination
Summary
Cereal –legume intercropping systems are assumed to provide high and stabilized yields in terms of quantity and quality (Ofori and Stern 1987; Jensen 1996; CorreHellou et al 2006), allow lower use of fertilizers and pesticides, and enhance biodiversity conservation (for a review see Malezieux et al 2009). Intercropping benefits result from a trade-off between complementarity (e.g. separate root and canopy areas) and competition processes (for light, water and nutrients) that occur between the component crops. Light capture drives biological nitrogen fixation by legume species and the autonomy of the intercropping system towards nitrogen resources. Its sharing in multi-specific stands appeared to be a crucial issue for managing the balance between the component species as well as for determining the final yield of the mixture. It has been proposed that increasing the light interception efficiency (LIE) of intercropping systems could be achieved through: (i) maximizing total light interception by improving the spatial and temporal ground cover and (ii) adequately sharing light between component species by improving their spatial and temporal complementarity (Sinoquet and Caldwell 1995)
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