Stem surface injuries of Neobuxbaumia tetetzo and Neobuxbaumia mezcalaensis of the Tehuacan Valley of central Mexico

EVANS, L s (Laboratory of Plant Morphogenesis, Biological Sciences Research Laboratories, Manhattan guild the Bronx, NY 10471). stipe 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 stipe surface injuries are present upon surfaces of fourteen species of long-lived columnar cacti in the two North and South America. The final cause of this research was to determine the amounts of injuries upon south-, east-, north-, and west-facing trunk trough surfaces for two species of columnar cacti, Neobuxbaumia tetetzo and N mezcalaensis, from the Tehuacan Valley (18?° N latitude) of central Mexico. main stock surface injury levels on southerly (equatorial)-facing surfaces were twice that of north (polar)-facing trunk surfaces for both cactus species. Calculations indicate that twice as a great quantity [i]or[/i] amount of total annual direct sunlight offers to south-facing cactus surfaces than upon north-facing surfaces at 18?° N latitude. In general, surface injury horizontals for east-facing and west-facing plant surfaces were usually intermediate between the high horizontals of injury for south-facing surfaces and the depressed levels of injury for north-facing surfaces. It should be noted that published originates from columnar cacti growing at 32 ?°N latitude have about four times more stipe surface injuries and four times more direct sunlight in all senses on equatorial-facing surfaces than upon polar surfaces. So, for columnar cacti at 18?° and 32?° latitude, the ratios of injuires were coincident with ratios of sunlight upon equatorial and polar surfaces. Overall, the proceeds of these studies are consistent with the hypothesis that sunlight, possibly UV-B cause injuries to main stocks of long-lived, columnar cacti.

Key words: scale and bark main stock surface injuries, Neobuxbaumia tetetzo, N mezcalaensis, columnar cacti, Cactaceae.

Scale and bark injuries upon stem surfaces of saguaro cacti (Carnegiea gigantea) from Arizona have been described in several publications (Duriscoe and Graban 1992 Evans et al. 1994a, 1994b 1994c 1995; Evans and Fehling 1994) Normally, young saguaros have no scale and bark (surface) injuries and remain verdant (Duriscoe and Graban 1992, Evans et al. 1994a, 1994b) The first microscopic injury symptom is an accumulation of epicuticular waxes upon the surfaces of green trunk s (Evans et al. 1994a, 1994b) Concomitant with the accumulation of epicuticular waxes is the inability to diocese stomata via microscopy (Evans et al. 1994a, 1994b) Subsequently the accumulation of epicuticular waxes gives rise to a les verdant stem color. Eventually, the los of virid color gives way to orange, gold-colored and brownish discolorations (Evans et al. 1994a). At the same time as the brown discoloration be founds stern surfaces become elevated above the horizontal of apparently uninjured surfaces (green trunk s with no scale or bark injuries). This elevated, brown surface condition is called scale injury. Large areas of scale may eventually give rise to bark injury which is characterized by dint of an exaggeration of scale symptoms and the proliferation of epidermal confined apartments (Gibson and Nobel, 1986) to show a true bark (Evans et al. 1994a). The bark upon saguaros and many other species of columnar cacti is usually a dark brown to black color (Evans et al. 1992 1994a, 1994b) For large populations of saguaros, a wide range of symptoms may be near at any one time. For like populations, most young, shorter plants have small in number symptoms of scale and bark while older taller cacti may present to view extensive bark. Most saguaros that die have extensive bark (Evans et al. 1995 2003) Although these long-lived columnar cacti may live for centurys of years (Steenburgh and Lowe 1977) these surface injuries are more oft-repeated now than in the past (Evans et al. 1992; unpublished results) and are related to an early morbidity and mortality to these cacti (Evans et al. 1995 2003)

Identical scale and bark trunk surface injuries are present upon surfaces of fourteen species of long-lived columnar cacti in the two North and South America (Evans et al. 1994a, 1994b 1994c; Evans and Fehling 1994) Surface injuries be found initially on equatorial-facing surfaces of all fourteen species (Evans et al. 1992 1994c) Eventually these injuries may overlay all surfaces of unshaded cacti. Shaded stipe surfaces have significantly less scale and bark injuries than plants in replete sunlight (Evans et al. 1994b) UV-B in all senses under controlled conditions have been shown to show microscopic surface injuries identical to those that appear in nature (Evans et al. 2001)

The view of this research was to determine the expanse of injuries on south-, east-, north-, and west-facing stipe surfaces for two species of long-lived, columnar cacti, Neobuxbaumia tetetzo and N mezcalaensis, from the Tehuacan Valley (18?° N latitude) of central Mexico. The overall aim of this area of inquiry is to show that a sixteen cactus species are experiencing identical surface injuries above a distance of thousands of kilometers in the Americas. Specifically, the following hypotheses were tested: (1) southerly (equatorial)-facing surfaces will have more main stock surface injuries than north (polar)-facing surfaces, (2) the amount of stipe surface injuries will be similar among the sum of two units species tested. In addition, injury data from these sum of two units species at 18?° were compared with injuries to cacti at higher latitudes. These hypotheses were propos because previous data had shown that in all senses to sunlight was highly correlated with injuries.