Evans, L. S. (Laboratory of Plant Morphogenesis, Biological Sciences Research Laboratories, Manhattan College, the Bronx, NY 10471). Stem surface injuries of Neobuxbaumia tetetzo and Neobuxbaumia mezcalaensis of the Tehuacan Valley of central Mexico. J. Torrey Bot. Soc. 132: 33–37. 2005.—Identical scale and bark stem surface injuries are present on surfaces of fourteen species of long-lived columnar cacti in both North and South America. The purpose of this research was to determine the amounts of injuries on south-, east-, north-, and west-facing stem trough surfaces for two species of columnar cacti, Neobuxbaumia tetetzo and N. mezcalaensis, from the Tehuacan Valley (18° N latitude) of central Mexico. Stem surface injury levels on south (equatorial)-facing surfaces were twice that of north (polar)-facing stem surfaces for both cactus species. Calculations indicate that twice as much total annual direct sunlight occurs to south-facing cactus surfaces than on north-facing surfaces at 18° N latitude. In general, surface injury levels for east-facing and west-facing plant surfaces were usually intermediate between the high levels of injury for south-facing surfaces and the low levels of injury for north-facing surfaces. It should be noted that published results from columnar cacti growing at 32 °N latitude have about four times more stem surface injuries and four times more direct sunlight exposure on equatorial-facing surfaces than on polar surfaces. So, for columnar cacti at 18° and 32° latitude, the ratios of injuires were coincident with ratios of sunlight on equatorial and polar surfaces. Overall, the results of these studies are consistent with the hypothesis that sunlight, possibly UV-B, cause injuries to stems of long-lived, columnar cacti.
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. 132 • No. 1