SGER: Potential Role of Ultraviolet Radiation in Tissue Injury of Columnar Cacti

最近的证据表明，高茎、长寿仙人掌的表皮褐变与总日照时间有关。北半球这类仙人掌的南暴露和南半球类似品种的北暴露的表皮褐变要大得多。这种表面褐化导致仙人掌个体死亡。一项对过去90年来亚利桑那州仙人掌的真实照片的评估表明，表皮褐变每十年增加约4%，这与美国过去30年来紫外线辐射的增加百分比相同。紫外线照射的增加已被证明与平流层中臭氧层的消耗有关。473个仙人掌的数据库已经能够显示出仙人掌表皮褐变的步骤序列。本研究的目的是对智利和阿根廷的几种仙人掌进行相同的物候和生理测量，以确定表皮褐变的步骤顺序是否与仙人掌相似。如果所有这些仙人掌（包括北半球和南半球）的步骤顺序是相似的，那么进一步研究紫外线伤害的可能机制的基础将得到加强。

Recent evidence shows that epidermal browning of tall- stemmed, long-lived cacti is related to total time of sun exposure. Epidermal browning is much greater on the southern exposures of such cacti in the Northern Hemisphere and on northern exposures of similar species in the Southern Hemisphere. This surface browning leads to death of individual cacti. An evaluation of authentic photographs of saguaro cacti an Arizona for the past 90 years shows that epidermal browning has increased by about 4% per decade, the same percentage increase in ultraviolet (UV) radiation exposure in the United States over the past three decades. The increase in ultraviolet light exposure has been shown to be related to the depletion of the ozone layer in the stratosphere. The data base (473 cacti) of saguaros has been able to show the sequence of steps during epidermal browning. The purpose of the proposed research is to make the same series of phenological and physiological measurements on several species of cacti in Chile and Argentina, to determine if the sequence of steps of epidermal browning is similar to those of saguaros. If the sequence of steps is similar among all these cacti (both Northern and Southern hemispheres), the basis for further investigation of a possible mechanism for UV-indeed injury would be strengthened.