Marciel José Ferreira

Estratégias no uso da energia luminosa por plantas jovens de Genipa spruceana Steyerm submetidas ao alagamento

In an attempt to elucidate strategies in the use of light energy by G. spruceana seedlings subjected to flooding, we investigated the capacity of light capture and use of light energy by G. spruceana in three growing conditions: 1- absence of flooding (SA), 2- partially flooded (PA) and 3- totally flooded (TA). Destructive and non-destructive measurements, such as specific leaf area, chloroplast pigment (chlorophyll and carotenoids) content and fluorescence analyses, were made at regular intervals over a period of 90 days. All parameters decreased in seedlings subjected to flooding. Plants of treatment TA dropped all of their leaves after 30 days of complete submergence. Chloroplast pigment content differed between treatments SA and TA after 30 days from the start of the experiment; whereas SA and PA plants only differed for this variable after 90 days. Plants subjected to flooding (PA and TA) exhibited high dissipation of photochemical de-excitation (DIo/ABS), indicating a limited efficiency of light energy use. This fact was proven by the performance index (PIABS) only in analyses after 90 days, and no significant difference was verified for PIABS among treatments up to 30 days. Therefore, considering that G. spruceana seedlings subjected to flooding reduced the chloroplast pigment content more quickly than PIABS, we suggest that the light energetic flux in G. spruceana seedlings subjected to flooding, in the beginning, is more restricted to a decrease in the structures that captures light (reduction chlorophyll pigment content) than how the photosynthetic apparatus functions (alterations in photochemical efficiency of photosystem II).

BIOMASSA, CRESCIMENTO E RESPOSTAS ECOFISIOLÓGICAS DE PLANTAS JOVENS DE Bertholletia excelsa BONPL. SUBMETIDAS A DIFERENTES NÍVEIS DE IRRADIÂNCIA

Brazil nut ( Bertholletia excelsa Bonpl.) is a light-demanding species, because in natural forest, the species depending of formation of clearings for reach reproduction size and in forest plantation, showing fast initial growth when exposed to high levels of irradiance. However, the ecophysiological traits of this species under contrasting conditions of irradiance were not investigated. In this study, in addition to growth traits, we investigated for first time the degree of plasticity of ecophysiological response of Bertholletia excelsa when subjected to contrasting irradiance environments. Young plants of Bertholletia excelsa were cultivated under three conditions of irradiance: low (20-300 µmol m -2 s -1 ), moderate (800-1000 µmol m -2 s -1 ) and high (1900-2100 µmol m -2 s -1 ). We analyzed the growth traits, gas exchange, chloroplastid pigment contents and, the end of experiment, the accumulation and partitioning of biomass. Young plants of Bertholletia excelsa showed the highest values of biomass, growth and photosynthesis when exposed to environments of moderate and high irradiance. Low irradiance condition stimulated more biomass partitioning for shoot and chloroplastid pigment contents. Bertholletia excelsa showed physiological plasticity under contrasting conditions of irradiance, the largest growth and biomass accumulation in environments of moderate and high irradiance were promoted by better photosynthetic performance, whereas the positive carbon balance under low irradiance is ensured by investment in structures of interception and energy harvesting.

Growth, biomass partitioning and photosynthesis of young plants of Genipa spruceana subjected to flooding

Genipa spruceana Steyerm (Rubiaceae) is a species often found in flooded environments in the central Amazonia. The objective of this study was elucidate possible adaptive strategies that enable this species to occupy environments under flooding, targeting the potential of the species for restoration of floodplains. In order to achieve these objectives growth traits, number of leaves, leaf expansion, biomass production, carbon assimilation and stomatal conductance were investigated in G. spruceana seedlings subjected to treatments: 1Non flooded plants (control –SA), 2partially flooded (PA) and 3completely flooded (TA) up to 90 days. Flooded treatments (PA and TA) induced smaller increments in all variables of height and diameter growth when compared to the control treatment. With increase of flooding, biomass allocation to leaves decreased until complete leaf abscission in TA, while increased in the stem. In PA treatment was observed reduction in C assimilation rates of 58% and 64% after 60 and 90 days, respectively, and 96% after 60 days in TA treatment. However, in the end of the experiment all treatments presented 100% of survival. Our results indicate that the loss of leaves and gain of the stem biomass can be protective strategy to alleviate the harmful effects of the flooding. On the other hand, the maxim survival rates suggest that G. spruceana exhibit high potential for establishment in frequently flooded areas.Genipa spruceana Steyerm (Rubiaceae) e uma especie frequentemente encontrada em ambientes alagados na Amazonia central. Neste estudo, objetivou-se elucidar possiveis estrategias adaptativas que permitem a especie ocupar ambientes sujeitos ao alagamento, visando ao potencial da especie para a restauracao de areas alagadas. No sentido de atingir tais objetivos foram investigadas caracteristicas de crescimento, numero de folhas, expansao foliar, acumulo de biomassa, assimilacao de carbono e condutância estomatica de plantas jovens de G. spruceana submetidas aos tratamentos: 1- controle (SA - sem alagamento), 2- plantas parcialmente alagadas (PA) e 3- plantas totalmente alagadas (TA) durante 90 dias. Os tratamentos de alagamento PA e TA induziram menores incrementos em todas as variaveis de crescimento em altura e diâmetro quando comparados ao tratamento controle. Com o aumento do nivel de inundacao, a alocacao de biomassa para a folha diminuiu ate a completa abscisao foliar em TA, enquanto aumentou a massa caulinar. No tratamento PA, foi observada reducao nas taxas de assimilacao de carbono da ordem de 58% e 64% aos 60 e 90 dias, respectivamente, e de 96% aos 60 dias no tratamento TA. Entretanto, ao final do experimento todos os tratamentos apresentaram 100% de sobrevivencia. Os resultados obtidos indicam que a perda de folhas e o ganho de biomassa no caule podem ser estrategias para atenuar o efeito prejudicial do alagamento. Por outro lado, as maximas taxas de sobrevivencia sugerem que G. spruceana exibe alto potencial para estabelecimento em ambientes frequentemente alagados.