Decoupling of light intensity effects on the growth and development of C3 and C4 weed species through sucrose supplementation

Abstract

Light availability has a profound effect on plant growth and development. One of the ways to study the effects of light intensity on plant growth and development without the confounding problem of photosynthate availability is sucrose injection/supplementation. A greenhouse experiment was conducted to evaluate the effects of light levels (0% and 75% shade) and sucrose injection (distilled water or 150 g sucrose l(-1)) on three weed species: redroot pigweed (Amaranthus retroflexus L., C4), lambsquarters (Chenopodium album L., C3) and velvetleaf (Abutilon theophrasti Medic., C3). The average total sucrose uptake was 7.6 and 5.9 g per plant for 0% and 75% shading, respectively, representing 47% of the average total weed dry weight. Plants injected with sucrose had greater dry weights and shoot-to-root ratios under both light levels. In spite of sucrose supplementation the reduction in dry matter due to shading was greater for roots and reproductive structures than vegetative shoot tissues, indicating light level regulation of morphological changes resulting in changed C allocation that are independent of photosynthate availability. Dry weights of plants injected with sucrose under 75% shading were not different from distilled water-injected unshaded plants. However, both sucrose-injected and control plants, regardless of their photosynthetic pathways, underwent similar changes in allocation of dry matter and morphology due to shading, suggesting that these effects are strictly due to light intensity and not related to photosynthate availability.

The biology of Canadian weeds. 130. Amaranthus retroflexus L., A. powellii S. Watson and A. hybridus L.

“…Stems of A. retroflexus in the growth chamber elongated more under a low ratio of red to far red light than under a high ratio (Ballaré et al 1991;Rajcan et al 2002), or at low compared with high PPFD (Begna et al 2002;Rajcan et al 2002). Similarly, the rate of leaf appearance and number of branches was reduced under low PPFD or by a corn canopy (McLachlan et al 1993a, b;Rajcan et al 2002).…”

Infestation of weed species in monocrop coffee or intercropped with banana, under agroecological system

“…Two factors are usually associated with the level of weed occurrence in cropping systems: the exudation of compounds with allelopathic activity to soil (Khan et al, 2012), and the direct effect of shading, which results in competition for light in qualitative and quantitative terms (Begna et al, 2002). Banana tree is not known to produce potent allelopathic compounds, but on the other hand its effects on the inhibition of weed occurrence is confirmed (Espindola et al, 2000).…”

Effect of planter and tractor wheels on row and inter-row weed populations

“…However, this effect was not observed for weed cover. We can only speculate that the shade of the soybean plants resulted in increased leaf area per biomass unit of some weeds (Pugnaire and Vallares, 2007) or reduced biomass allocation to roots in weeds (root biomass was not measured in this study) (Begna et al, 2002).…”