Alena Torres Netto

BORON DEFICIENCY AFFECTS GAS EXCHANGE AND PHOTOCHEMICAL EFFICIENCY (JPI TEST PARAMETERS) IN GREEN DWARF COCONUT

Boron (B) deficiency causes a wide array of symptoms, not only among species of palms, but also within a single species (i.e. Cocos nucifera). A better understanding of the effects of B deficiency in coconut will be important to try optimizing a rational fertilization management in coconut plants. Thus, modification of PSII photochemistry (using a group of fluorescence parameters, called the JIP- test, that quantify the stepwise flow of energy through Photosystem II) and gas-exchange in boron deficient green dwarf coconut plants were investigated. Our results suggest that a modification of PSII photochemistry (non-stomatic effects) and gas-exchange (stomatic effects) were induced by boron deficiency. Such modifications are manifested by (1) increase the ratio of total dissipation to the amount of active reaction centers (RCs) [dissipation (DI)/RC] and (2) leaf-to-air vapor pressure difference (VPDleaf-air). These modifications (on PSII photochemistry and gas-exchange) were caused by a decrease in energy absorbed per excited cross-section [absorption flux (ABS)/cross section of the sample (CS0)], density of active reaction centers (RC/CS), maximal trapping rate of an exciton that will lead to QA reduction measured over a cross- section of active and inactive RCs [trapping flux (TR)/CS0], electron transport per excited cross-section [electron transport flux (ET0)/CS)], area above curve (proportional to the pool size of the electron acceptors QA on the reducing side of PSII), photosynthesis (A), stomatal conductance (gs), transpiration (E), chlorophyll concentration (SPAD readings), growth parameters (root DW and height plant). Our results demonstrate that by analyzing fluorescence (JIP test parameters) derived from the polyphasic fluorescence transients measurements were able to estimate the functional changes of PSII in B deficient coconut plants. The results in this study suggest that fluorescence analysis (JIP test) and instantaneous measurements of gas-exchange can be useful tools in assessing the physiological effects of B deficiency in green dwarf coconut.

Brassinosteroid analogue affects the senescence in two papaya genotypes submitted to drought stress

Brassinosteroids (BS) application is associated with the increase of tolerance to some kinds of stresses, such as those induced by the infection of pathogens, temperature, salt and water deficiency. In this work, the influence of a spirostanic analogue of brassinosteroid (SAB) in the leaves of papaya Golden and UENF/CALIMAN 01 (UC 01) was tested to evaluate alterations in the content of chlorophyll in plants submitted to drought stress (DS). When plants were 70 d old, SAB was applied (0,1 mg L-1) for five consecutive days in half of the plants meant for the experiment. The treatments were: control irrigated (I), I with SAB (IB), DS and DS with SAB (DSB). The evaluated leaves were marked in accordance to the age: LEAF 1 (youngest expanded leaf), LEAF 2 (insertion immediately below LEAF 1) and LEAF 3 (insertion immediately below LEAF 2). The same leaves were used throughtout the experimental period. After the thirteenth day, the chlorophyll contents of DSB (Golden and UC 01) were always lesser than the treatment DS in LEAF 2. The irrigation was restarted in stressed plants on the fifteenth day, followed by new application of SAB (IB and DSB treatments). In Golden plants, DSB showed the lowest values of chlorophyll contents after re-watering, while in UC 01, differences in chlorophyll contents between treatments DS and DSB had not occurred. Alterations in Fv/Fm relation did not occur among the treatments during stress. In genotype UC 01, the irrigated plants showed minor values of Fv/Fm at the end of the experiment, whereas the plants submitted to DS presented increments in this relation in this same time. These results indicate that SAB might have contributed to accelerate the rate of leaf senescence of the oldest leaves of stressed plants, redistributing photoassimilates and other compounds for the youngest leaves.

Morphological analysis and photosynthetic performance of improved papaya genotypes

Brazil is the largest world producer of papaya and the third largest exporter despite of only 1.5 to 2.0% of its production is exported. Such an underexplored exportation potential highlight the necessity for physiological studies on new cultivars and hybrids to verify their agronomic and commercial viability. Two Brazilian states, Bahia and Espirito Santo, are responsible for 80% of national production. Papaya can also be an agricultural alternative to north / northeast of Rio de Janeiro, because the region is close to consumer centers and have similar environmental conditions of the most productive regions. Nevertheless, it is worth to develop cultivars that can express the highest yield potential in this region. The aim of this work was to characterize physiologically two hybrids developed for the north/northeast of Rio de Janeiro (UENF/Caliman 01 and JS12) in comparison with three top commercial genotypes (Golden, Sunrise Solo 7212 and Tainung) of Caricapapaya L. The cv. Golden presented the lowest shoot and root growth, the lowest height, shrunk diameter, specific leaf weight, less efficiency in electrons transport per sample area and show the lowest ability to synthesized total chlorophylls in comparison with the others genotypes. At noon, this genotype showed higher stomatal conductance, related to the leaf-air vapor pressure deficit, which lead to higher transpiration rate and intrinsic water use efficiency. No differences were detected in the photosynthetic rates among the five genotypes suggesting that the UENF`s hybrids are endowed with similar photosynthetic capacity and morphological characteristics to the top commercial genotypes. The relevance of this characterization to drive future successful genetic improvement programs will be discussed.

Mancha fisiológica do mamão 'formosa': relações com o potencial hídrico do solo, o teor de sólidos solúveis totais do látex e as variáveis do clima

Em varias regioes produtoras de mamao do Brasil, tem sido observado um disturbio fisiologico nos frutos denominado de Mancha Fisiologica do Mamao (MFM). Tal disturbio pode causar significativos prejuizos ao produtor, uma vez que pode comprometer a qualidade do fruto da especie. Procurou-se buscar, neste trabalho, possiveis relacoes entre a incidencia da MFM, o potencial hidrico do solo, o teor de solidos soluveis no latex, a amplitude termica e o deficit de pressao de vapor do ar. Para tanto, num plantio comercial localizado na cidade de Sao Francisco do Itabapoana - RJ, foram monitorados o deficit de pressao de vapor do ar, o potencial hidrico do solo, o teor de solidos soluveis no latex dos frutos em duas faces do fruto (face proxima ao tronco e face oposta ao tronco) e a amplitude termica do ar. Foi verificado que nos meses que antecederam a epoca de maior incidencia da MFM, o deficit hidrico do solo acentuado (media diaria -113,6kPa nos meses de abril a julho), em associacao com menores demandas evaporativas do ar (media diaria nos meses de abril a julho 0,6kPa) e uma amplitude termica media de 11,3oC nessas mesmas epocas, contribuiu para a maior incidencia da MFM, nos meses julho a outubro.

Papaya pulp gelling: is it premature ripening or problems of water accumulation in the apoplast?

ABSTRACT - Gelled aspect in papaya fruit is typically confused with premature ripening. This research reports the characterization of this physiological disorder in the pulp of papaya fruit by measuring electrolyte leakage, Pi content, lipid peroxidation, pulp firmness, mineral contents (Ca, Mg and K - in pulp and seed tissues), and histological analysis of pulp tissue. The results showed that the gelled aspect of the papaya fruit pulp is not associated with tissue premature ripening. Data indicate a reduction of the vacuole water intake as the principal cause of the loss of cellular turgor; while the waterlogged aspect of the tissue may be due to water accumulation in the apoplast.Index terms: ultrastructural alterations, cell turgor, fruit quality, physiological disturbances, biochemical alterations. GELEIFICACAO DA POLPA DE MAMAO: AMADURECIMENTO PREMATURO OU PROBLEMAS NO ACUMULO DE AGUA NO APOPLASTO? RESUMO - O aspecto geleificado da polpa de mamao e constantemente confundido com amadurecimento prematuro. Este trabalho caracterizou esse disturbio fisiologico na polpa de frutos de mamao atraves de medidas de liberacao de eletrolitos, conteudo de Pi, peroxidacao lipidica, firmeza da polpa, condudo mineral (Ca, Mg e K - na polpa e semente) e analises histologicas da polpa. Os resultados mostram que o aspecto geleificado da polpa de mamao nao esta associado com o amadurecimento prematuro. Os resultados indicam uma reducao da entrada de agua no vacuolo como a principal causa da perda de turgor celular, enquanto o aspecto encharcado da polpa pode ser devido ao acumulo de agua no apoplasto. Termos para indexacao: alteracoes ultra estruturas, turgor celular, qualidade de frutos, disturbios fisiolo-gicos, alteracos bioquimicas.

Eficiência fotossintética e crescimento de genótipos de abacaxizeiro cultivados in vitro em diferentes qualidades de luz, tipos de frasco de cultivo e concentrações de sacarose

Protocols for the micropropagation of pineapple cv. Vitoria and cv. IAC Fantastico were optimized, as well as the photosynthetic and growth responses of these genotypes in response to changing the in vitro environment. For the two cultivars, treatments were arranged in a completely randomized design, with six repetitions and five plants per repetition, in a sub plots subdivided, made up of light qualities (white and red), types of culture vessels (closed and ventilated) and sucrose concentrations in the growth medium (15 and 30 g L-1). The evaluation was made after 40 days of in vitro culture. Under the conditions of this study there was no photosynthetic carbon assimilation. This non-assimilation was associated with biochemical compromises rather than photochemical efficiency. The presence of sucrose should be the factor responsible for non-CO2 assimilation. The cv. Vitoria showed higher growth than the cv. IAC Fantastico due to the higher carbon absorption via sucrose.

ECOFISIOLOGIA DE PLANTAS DE Coffea canephora PIERRE CULTIVADAS EM CONDIÇÕES DE CONFINAMENTO DO SISTEMA RADICULAR: INFLUÊNCIAS SOBRE A NUTRIÇÃO MINERAL

Coffea canephora Pierre plants were grown in five pot sizes (50, 100, 200, 300 and 3.400mL), filled with Plantmax . The plants grew under screen with 50% of interception of the photosynthetic photons flux (PPF). A sprinkle intermittent irrigation system was used. From 17 th to 20 th weeks after transplantation (WAT) nitrogen solution (N) was applied directly in the substrate. From 22 th to 28 th WAT complete nutrient solution (CNS) was applied by water irrigation. The aim of this work was to quantify, in a time scale, the influence of different volume recipients in nutrient composition (total-N, P, K, Ca and Mg), in the shoot under root restriction conditions. Reductions were observed in total-N and K contents in all pots sizes until 20 th WAT. These nutrient contents in the shoot of 3400mL plants, showed a higher total-N value in 12 th and to K in the 12 th and 16 th WAT. Plants showed a decline in P contents until the 20 th WAT. The plants in 50, 100, 200 e 300mL pot sizes had a lower response to CNS application after the 22 th WAT. After the application of CNS, it was verified a higher concentration of total-N and K in cultivated plants in all volume recipients. The plants showed a increase in Ca and Mg contents after 12 th WAT in all volume recipients.