Photosynthetic benefits of ultraviolet-A to Pimelea ligustrina, a woody shrub of sub-alpine Australia.

The definition of photosynthetically active radiation (Q) as the visible waveband (λ 400-700 nm) is a core assumption of much of modern plant biology and global models of carbon and water fluxes. On the other hand, much research has focused on potential mutation and damage to leaves caused by ultraviolet (UV) radiation (280-400 nm), and anatomical and physiological adaptations that help avoid such damage. Even so, plant responses to UV-A are poorly described and, until now, photosynthetic utilization of UV-A has not been elucidated under full light conditions in the field. We found that the UV-A content of sunlight increased photosynthetic rates in situ by 12% in Pimelea ligustrina Labill., a common and indigenous woody shrub of alpine ecosystems of the Southern Hemisphere. Compared to companion shrubs, UV-A-induced photosynthesis in P. ligustrina resulted from reduced physical and chemical capacities to screen UV-A at the leaf surface (illustrated by a lack of cuticle and reduced phenol index) and the resulting ability of UV-A to excite chlorophyll (Chl) a directly, and via energy provided by the carotenoid lutein. A screening of 55 additional sub-alpine species showed that 47% of the plant taxa also display Chl a fluorescence under UV-A. If Chl a fluorescence indicates potential for photosynthetic gain, continued exclusion of UV-A from definitions of Q in this ecosystem could result in underestimates of measured and modeled rates of photosynthesis and miscalculation of potential for carbon sequestration. We suggest that carbon gain for alpine environs across the globe could be similarly underestimated given that UV-A radiation increases with altitude and that the frequently dominant herb and grass life-forms often transmit UV-A through the epidermis.

The evolution of angiosperm lianescence without vessels--climbing mode and wood structure-function in Tasmannia cordata (Winteraceae).

• The lack of extant lianescent vessel-less seed plants supports a hypothesis that liana evolution requires large-diameter xylem conduits. Here, we demonstrate an unusual example of a lianoid vessel-less angiosperm, Tasmannia cordata (Winteraceae), from New Guinea. • Wood mechanical, hydraulic and structural measurements were used to determine how T. cordata climbs and to test for ecophysiological shifts related to liana evolution vs 13 free-standing congeners. • The tracheid-based wood of T. cordata furnished low hydraulic capacity compared with that of vessel-bearing lianas. In comparison with most nonclimbing relatives, T. cordata possessed lower photosynthetic rates and leaf and stem hydraulic capacities. However, T. cordata exhibited a two- to five-fold greater wood elastic modulus than its relatives. • Tasmannia cordata provides an unusual example of angiosperm liana evolution uncoupled from xylem conduit gigantism, as well as high plasticity and cell type diversity in vascular development. Because T. cordata lacks vessels, our results suggest that a key limitation for a vessel-less liana is that strong and low hydraulically conductive wood is required to meet the mechanical demands of lianescence.

Estrutura populacional e incremento corrente anual de casca-de-anta (Drimys brasiliensis Miers - Winteraceae) em Caçador, Santa Catarina, Brasil / Population structure and annual increment in "casca-de-anta" (Drimys brasiliensis Miers - Winteraceae) from Caçador Municipality, Santa Catarina State, Brazil

Drimys brasiliensis Miers, conhecida como cataia ou casca-de-anta, é árvore nativa da Mata Atlântica e as cascas tem sido utilizadas medicinalmente a partir da exploração de plantas em populações naturais. Este trabalho teve como objetivo estudar a demografia de duas populações naturais de D. brasiliensis, (1) Reserva Genética Florestal de Caçador (RGFC) e (2) Floresta Nacional de Caçador (FLONA), ambas no município de Caçador (SC), visando fundamentar estratégias de exploração sustentável e conservação deste recurso florestal não-madeireiro. A maior luminosidade no sub-bosque existente na FLONA atuou positivamente na espécie, aumentado a capacidade de incremento em diâmetro à altura do peito (DAP), altura (H) e área basal (AB), além de antecipar a reprodução em plantas de menor porte. A análise do padrão espacial das plantas reprodutivas na RGFC mostrou padrão agregado, e na FLONA até a distância de 25 metros. Esse comportamento indicou que a espécie apresenta potencial de manejo em florestas secundárias, formação sucessional em que se encontra a maioria dos remanescentes de Mata Atlântica, além de indicar potencial para cultivo em sistemas agroflorestais.

Known as "cataia" or "casca-de-anta", Drimys brasiliensis Miers is a tree native to the Atlantic Forest and its barks have been medicinally used by exploring natural populations. The present work aimed to study the demography of two D. brasiliensis natural populations, (1) Caçador Forest Genetic Reserve (RGFC) and(2) Caçador National Forest (FLONA), both located in Caçador Municipality, Santa Catarina State, Brazil, in order to establish strategies for sustainable exploration and conservation of such non-timber forest resource. The higher luminosity in FLONA understory was beneficial to the species by increasing their increment capability regarding diameter at breast height (DBH), height (H) and basal area (BA), and made the reproduction in smaller plants earlier. The spatial analysis of reproductive plants in RGFC had an aggregate pattern, whereas in FLONA until 25m distance was detected. Such results indicated that this species presents potential for management in secondary forests, the successional formation where the major Atlantic Forest remnants are found, as well as potential for cultivation in agroforestry systems.