Daniela Cassol

An evaluation of non-destructive methods to estimate total chlorophyll content

The portable chlorophyll (Chl) meter (CL-01, Hansatech) has been successfully used for a rapid and direct estimation of total Chl content in the leaves of some crops. We compared CL-01 meter readings (Chl value) and Chl contents in leaves of Zea mays, Cucumis sativus, Raphanus sativus, and Ceiba speciosa. Chl index was linearly and positively correlated to Chl content in all the species.

CRESCIMENTO E PARTIÇÃO DE ASSIMILADOS EM CULTIVARES DE ARROZ DIFERINDO NO POTENCIAL DE PRODUTIVIDADE DE GRÃOS

Foram estudados o crescimento, a particao de assimilados e a producao de graos nas cultivares de arroz BRS Pelota (maior produtividade) e BRS Firmeza (menor produtividade). O experimento foi realizado em casa de vegetacao, com plantas cultivadas em vaso. Utilizou-se o delineamento experimental inteiramente casualizado, com duas cultivares, nove coletas e quatro repeticoes por tratamento. Com a cultivar BRS Pelota houve maior acumulo de materia seca total (Wt), principalmente no fim do ciclo, bem como maior area foliar (Af). A materia seca alocada para o colmo + bainha e as paniculas tambem foi maior em BRS Pelota. Porem, a porcentagem de Wt destinada as paniculas aos 125 DAE foi semelhante entre as cultivares. Em BRS Firmeza, o aumento em Wt nas raizes pode ter influenciado o direcionamento de fotoassimilados para os graos e contribuido para o atraso na senescencia das plantas. A produtividade de BRS Pelota foi maior que a de BRS Firmeza (17,4 contra 11,8 g por vaso) e seu numero de paniculas por planta por vaso foi tres vezes superior em relacao a cultivar BRS Firmeza. O componente de producao de maior expressao no rendimento foi o numero de paniculas. A maior produtividade da cultivar BRS Pelota pode estar relacionada a maior area foliar e sua duracao, o que permite o fornecimento de elevada quantidade de fotoassimilados por um periodo maior.

Chlorophyll a fluorescence study revealing effects of flooding in canola hybrids

By generating stress conditions soil flooding can induce alterations in the cell metabolism and thus is detrimental to plant growth. This study was done under the greenhouse conditions to determine the effect of soil flooding on the chlorophyll fluorescence of some hybrids of canola (Brassica napus L.). Fifty five days old plants were subjected to flooding for six days. There was no difference in the parameters modulate chlorophyll fluorescence, in contrast, some the parameters related to the energy flux in photosystem II varied due to flooding stress. At the end of the six days, the performance indexes (PItotal and PIABS) decreased, in all hybrids except in ‘Hyola 420’. The difference kinetics of the chlorophyll a fluorescence transient showed different effects on different sites of the photosynthetic machinery. It could be concluded that compared to the other hybrids, ‘Hyola 420’ was less sensitive to flooding.

Chlorophyll a fluorescence as indicative of the salt stress on Brassica napus L.

The effects of salinity stress on chlorophyll fluorescence and the growth of Brassica napus L were investigated. The chlorophyll a fluorescence transient were recorded and analyzed according to the JIP-test which can quantify PSII performance. Salt stress resulted in decreased leaf area and dry matter compared with the control treatment (0 mM NaCl). The most pronounced effects of salt stress were observed with 200 mM NaCl, and the hybrids displayed different levels of sensitivity to stress. The Performance Index (PIABS) was the most sensitive parameter to salt stress, which suggests that this parameter can be used to screen genotypes for salt tolerance.

Características fotossintéticas de batata cv. Baronesa e seu genótipo transformado geneticamente para resistência ao PVY

Potato breeding is difficult and requires a great deal of time and energy. The use of recombinant DNA technology, with its potential capacity of isolating and transferring genes from any organism, allows incorporating in plants new characters of agricultural interest. However, consequences of the incorporation of determined genes on physiological characteristics are sometimes unknown. In this study we evaluated photosynthetic characteristics of potato plants genetically modified with resistance genes to PVY. Potato tubers of cv. Baronesa and its respective transformed genotype were planted in pots and kept in greenhouse. During the plant life cycle, parameters of chlorophyll fluorescence, net photosynthesis and potential photosynthesis were evaluated. Plants transformed with PVY resistant genes showed higher maximum photochemical efficiency and higher oxygen evolution rate, however the parameters of chlorophyll fluorescence and net photosynthesis were the same.