Correlates of leaf optical properties in tropical forest sun and extreme-shade plants

Thirteens hade-adaptedr ain forest species were comparedw ith twelve sun-adaptedt ropical forest species for correlates to leaf optical properties (described previously in Amer. J. Bot. 73: 1100-1108). The two samples were similar in absorptance of quanta for photosynthesis, but the shade-adaptedt axa: 1) had significantlyl ower specificl eaf weights,i ndicatinga more metabolically efficient production of surface for quantum capture; 2) synthesized less chlorophyll per unit area; and 3) used less chlorophyll for capturing the same quanta for photosynthesis. The anatomical features that best correlate with this increased efficiency are palisade cell shape and chloroplast distribution. Palisade cells with more equal dimensions have more chloroplasts on their abaxial surfaces. This dense layer of chloroplasts maximizes the light capture efficiency limited by sieve effects. The more columnar palisade cells of sun-adapted taxa allow light to pass through the central vacuoles and spaces between cells, making chloroplasts less efficient in energy capture, but allowing light to reach chloroplasts in the spongy mesophyll. Pioneer species may be an exception to these two groups of species. Three pioneer taxa included in this study have columnar palisade cells that are extremely narrow and packed closely together. This layer allows little penetration of light, but exposure of the leaf undersurface may provide illumination of spongy mesophyll chloroplasts in these plants.

Leaf Optical Properties of Rainforest Sun and Extreme Shade Plants

The opticalp ropertieso f the leaves of twelve tropicals un speciesa nd thirteent ropicale xtreme shade species were examinedw ith an integratings pherea ttachedt o a spectroradiometerM. easurements of diffuse reflectance and transmittance allowed calculations of absorptance, 350- 1,100 nm. Althoughs ome shade species absorbedh igherp ercentageso f quantumf lux densities for photosynthesis (400-700 nm, PPFD) than the mean for the sun species, the sun and shade species as groups were not significantly different from each other: 90.2, S.D. 3.6% for shade species and 88.6, S.D. 2.4% for the sun species. The groups of species did not differ in total absorptance of energy 350-1,100 nm. Furthermore, the sun and shade species were identical in theirs hifto f absorptancea t wavelengthsb etween6 50 and 750 nm. The anthocyanicc oloration of the leaf undersurfaceso f two species polymorphicf or this characteristic( Trionela hirsuta and Ischnosciphonp ruinosus)i s correlatedw ith increaseda bsorptancea t the uppere nd of the action spectrum of photosynthesis. Although sun and shade species have similar optical properties, the energy investment (as documented by dry wt per unit area of leaf surface) is much less for the shade species.

Eden in the age of the fifth sun: The narrative work of Homero Aridjis

Homero Aridjis (b. 1940) is a major Mexican poet, novelist, essayist and ecological activist whose prolific body of work, ranging over forty years and including more than eleven volumes of poetry and thirteen novels, has yet to be studied as a coherent literary corpus in the context of recent Latin American fiction. The purpose of this dissertation was to analyze the narrative works of this author as both illustrative of the changes that have occurred in Latin American fiction since the 1960s when it first burst onto the world scene, as well as to study the uniqueness of this particular author's view of literature as it relates to historical discourse, apocalypticism. and social commitment. ^ Research showed that in the case of the narrative style of Aridjis, major trends in the contemporary Latin American novel were present in such a profuse and model manner as to confirm this author's importance as a prime example of what is commonly known as “Post-Boom” fiction. However, beyond the mere presence of literary elements, this study showed that the author's unique approach to narrative style has altered and expanded the aesthetic and thematic possibilities of the contemporary novel. The area where this is most clearly seen is in his experimentation with the historical genre. By manipulating the referential techniques of what has lately come to be known as the “new historical novel,” Aridjis has written both a cycle of purely historical novels and a cycle of futuristic ones that attempt to transcend the temporal limits traditionally imposed by these narrative forms, fusing them into one constant questioning of the nature of love, hate and identity. In this manner, he has developed a “simultaneist” narrative approach where distinct historical and imagined periods, places, people, things, and texts coexist and interact, widening almost to delirium the interpretative possibilities of the work. ^ This unique view of time and narrative, together with the author's political activism and millenarian view of history, make the novels of Homero Aridjis an important element in understanding the continuing development and evolution of Latin American fiction at the turn of the century. ^