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1 September 2011 Photosynthetic Rates of Two Species of Malvaceae, Malvaviscus arboreus var. drummondii (Wax Mallow) and Abutilon theophrasti (Velvetleaf)
O. W. Van Auken, J. K. Bush
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Abstract

We examined two co-occurring species of Malvaceae in the savanna of central Texas to determine their photosynthetic response to varying levels of light. Abutilon theophrasti had a mean (±1 SD) density of 4 ± 4 plants/m2 in the open-grassland phase of the savanna, and a density of 1 ± 2 plants/m2 under canopy of woody mottes. Malvaviscus arboreus var. drummondii was not in the open-grassland phase and had a density of 3 ± 6 plants/m2 under canopy of woody mottes. Mean midday levels of light in the open and canopy were significantly different at 2,004 versus 192 µmol/m2/s, respectively. Maximum photosynthetic rate of A. theophrasti (34.6 ± 3.6 µM CO2/m2/s) occurred at a photosynthetic-flux density of 2,000 ± 0.0 µM /m2/s and was significantly greater than the maximum photosynthetic rate of M. arboreus var. drummondii (14.8 ± 2.2 µM CO2/m2/s), which occurred at a photosynthetic-flux density of 1,350 ± 173.0 µM /m2/s. Light saturation, light-compensation point, dark respiration rates, stomatal conductance, and transpiration rates for A. theophrasti were higher than rates of M. arboreus var. drummondii. These species have significant differences in most gas-exchange measurements, reflecting differences in their habitats. Based on these differences, M. arboreus var. drummondii is a sun–shade intermediate and A. theophrasti is a sun plant. However, maximum-photosynthetic-rate values and levels of light at maximum photosynthetic rate suggest that M. arboreus var. drummondii would do well in edge or partially shaded habitats.

O. W. Van Auken and J. K. Bush "Photosynthetic Rates of Two Species of Malvaceae, Malvaviscus arboreus var. drummondii (Wax Mallow) and Abutilon theophrasti (Velvetleaf)," The Southwestern Naturalist 56(3), 325-332, (1 September 2011). https://doi.org/10.1894/F04-MLK-13.1
Received: 1 January 2009; Accepted: 1 June 2011; Published: 1 September 2011
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