ABSTRACT We discuss evidence of effects of an accidental fire on shoot growth and leaf development in six cerrado tree species with distinct leaf phenologies. Buds of all six species were marked before shoot and leaf emergence in the dry season. After fire, leaf and shoot growth were monitored weekly and specific leaf area (SLA) was determined. Shoot order was determined in the growing season. Evergreens and semideciduous woody species had rapid leaf and shoot growth and decreased leaf life span (LLS) after fire compared with published data for evergreens in cerrado areas without fire. On the other hand, Kielmeyera variabilis, a deciduous species, showed intense branching and produced two orders of shoots in one growing season. Fires promote rapid leaf and shoot growth in evergreens owing to reserve accumulations that allow survivorship after disturbances. However, the leaves produced by evergreens after fire had high SLAs and were discarded before the next rainy season (short LLS). This leaf cohort was produced with less carbon per leaf, and the decreased LLS prevented herbivory and water loss during the dry season. Fire is an important factor of cerrado environments, influencing leaf production and shoot architecture in cerrado trees.

As relações entre a inclinação do ramo, irradiância e as características morfofisiológicas de folhas basais (FB) e distais (FD) foram investigadas em seis espécies arbóreas de Cerrado com distintas fenologias foliares. Espécies decíduas apresentaram ramos plagiotrópicos (44º) e maior área foliar do que espécies semidecíduas e sempreverdes com ramos ortotrópicos (56º e 63º, respectivamente). Nas espécies decíduas a irradiância solar foi de 85% na base do ramo, mas nas espécies semidecíduas e sempreverdes menos de 23% da irradiância incidiu nas FB. As decíduas apresentaram fotossíntese líquida máxima (Pnmax) equivalente entre FB e FD, porém, nas semidecíduas e sempreverdes ocorreu uma diminuição significativa de Pnmax nas FB. Os ramos plagiotrópicos das decíduas permitiram uma equivalente irradiância solar e similar Pnmax ao longo do ramo. De forma contrastante, os ramos ortotrópicos das semidecíduas e sempreverdes resultaram em intenso sombreamento e diminuição de Pnmax nas FB. Considerando conjuntamente FB e FD, não houve um gradiente significativo dos valores do tempo de vida da folha (TVF) ou Pnmax entre decíduas, semidecíduas e sempreverdes. A inclinação do ramo e o sombreamento correspondente entre as folhas são importantes fatores para a determinação de Pnmax ao longo dos ramos nas espécies arbóreas de Cerrado. Por outro lado, quando FB e FD foram consideradas conjuntamente não houve diferença de Pnmax entre os grupos fenológicos estudados devido à similaridade do TVF.

This study investigated the relationship among shoot inclination, irradiance and morphophysiological traits of basal (BL) and distal (DL) leaves in six cerrado trees with distinct leaf deciduousness. Deciduous species showed plagiotropic shoots (44º) and larger leaf area than semideciduous and evergreen species, which showed orthotropic shoots (56º and 63º, respectively). Despite larger leaf area, irradiance at shoot base in deciduous was around 85% in relation to full irradiance, while in semideciduous and evergreen only 23% of irradiance reached on BL. Likewise, maximum net photosynthesis (Pnmax) was similar between BL and DL in deciduous. Contrastingly, semideciduous and evergreen showed significant decreasing of Pnmax in BL. Plagiotropic shoots of deciduous allow similar irradiance along shoots, resulting in similar Pnmax along shoot. On the other hand, orthotropic shoots of semideciduous and evergreen resulted in shading and decreasing of Pnmax on BL. However, considering BL and DL together, there was not significant difference of leaf-life-span or Pnmax among deciduous, semideciduous and evergreen. Therefore, shoot inclination and shading among leaves on same shoot should be significant influencing leaf morphophysiological traits along shoots in cerrado trees. On the other hand, similar leaf-life-span among phenological groups resulted in absence of Pnmax differences when BL and DL were considered together.

Variações na morfologia e alocação de biomassa em folhas e ramos foram investigadas em 15 espécies arbóreas de Cerrado com distintas fenologias foliares e crescendo em condições naturais. As espécies decíduas apresentaram maiores valores que as sempreverdes para razão entre massa de folhas e do ramo, área foliar individual, área foliar por ramo, índice de exposição foliar e número de folhas pelo comprimento do ramo. As diferenças acerca das relações ramo-folhagem entre os grupos fenológicos poderia ser explicada pelos ramos plagiotrópicos nas decíduas e pelos ramos eretos nas semidecíduas e sempre verdes. Ramos plagiotrópicos propiciam similar irradiância incidente ao longo do ramo e alta alocação de biomassa em favor das folhas sem auto-sombreamento da folhagem nas decíduas. A variação estrutural entre ramos curtos e longos foi indicada por uma relação exponencial entre o índice de exposição foliar com o comprimento do ramo em todas decíduas, em três semidecíduas e duas sempreverdes. Assim, especialmente nas decíduas, ramos curtos apresentam maior área foliar por comprimento de ramo do que ramos longos. A diferenciação entre ramos curtos e longos depende do comprimento do ramo nas decíduas em função do número de folhas no ramo ser pré-determinado nas gemas. Diferentemente, a neo-formação de folhas nas semidecíduas e sempreverdes mantêm mais constante a relação ramo-folhagem por comprimento de ramo, em função da folhagem ser produzida de acordo com o crescimento do ramo durante o ano. Em conclusão, a persistência da folhagem, inclinação de ramo, tipo de produção foliar, e alocação de recursos entre os componentes autotróficos e heterotróficos da copa são características interdependentes nas espécies arbóreas de Cerrado ao longo dos distintos grupos fenológicos foliares.

The morphology and the biomass allocation in shoots and leaves were investigated in 15 cerrado tree species with distinct leaf phenology growing under natural conditions. Higher values of leaf/shoot ratio on mass base, individual leaf area, leaf area per shoot, leaf display index, and leaf number per shoot length were found in deciduous than in evergreen species. The differences about shoot-foliage relationship across leaf phenological groups could be explained by plagiotropic shoots on deciduous and by erect shoots in semideciduous and evergreen species. Plagiotropic shoots allow similar irradiance along shoots and high biomass allocation in favor of leaves without foliage self-shading in deciduous tree species. The structural differentiation between short and long shoots was indicated by an exponential relationship between leaf display index and shoot length in all deciduous, in three semideciduous, and in two evergreen species. Therefore, especially in deciduous, the short shoots had higher leaf area per unit of length than the long shoots. The differentiation between short and long shoots depends on the shoot length in deciduous because of the leaf number on shoot is predetermined in buds. Contrastingly, the leaf neo-formation in semideciduous and in evergreen tree species keeps the shoot-leaf relationship per shoot length more constant, because of the foliage being produced according to the shoot growth during the year. In conclusion, the foliage persistence, the shoot inclination, the type of leaf production and the resources allocation between autotrophic and heterotrophic vegetative canopy parts are interdependent in cerrado tree species across different leaf phenological groups.