Cacti of the genus Opuntia are an economically important crop. Understanding the mechanisms they possess to protect against UV radiation is important for assessing their possible response to climatic change. Measurements of the concentrations of UV-screening compounds and epidermal transmittance for two species of platyopuntia, Opuntia engelmannii Salm-Dyck. and O. phaeacantha Engelm. during 1998 and 1999 were used to investigate the UV-protection afforded by the cactus epidermis. A UV-radiative transfer model was used to investigate the interception of UV radiation on differently oriented surfaces. We show that vertical morphology itself confers significant protection against UV radiation compared to a horizontal surface. Concentrations of UV-screening flavonoids were found to vary depending on the UV exposure of different surfaces. West-facing surfaces had lower concentrations than east-facing surfaces, although theoretically they should be identical. This might be explained by the higher mean temperatures on west-facing surfaces. Although UV-absorbing soluble flavonoids in the epidermis block both UV-B and UV-A, the structure of the epidermis alone may be sufficient to remove up to 94% of the UV-B portion of the spectrum. These data yield insights into possible mechanisms of recent declines in cacti populations.
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.