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.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 56 • No. 3