Scielo RSS <![CDATA[Brazilian Journal of Plant Physiology]]> vol. 23 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Chlorophyll <i>a</i> fluorescence as indicative of the salt stress on <i>Brassica napus </i>L.</b>]]> 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 (PI ABS) was the most sensitive parameter to salt stress, which suggests that this parameter can be used to screen genotypes for salt tolerance. <![CDATA[<b>Effects of hydric deficiency on gas exchange parameters and metabolism of <i>Eucalyptus grandis</i> clones</b>]]> The metabolic effects caused by hydric deficiency (HD) on Eucalyptus grandis clones were assessed by an experiment where plants were cultivated in four blocks. The first was the control block, normally irrigated, whereas the other three blocks were submitted to cycles of hydric deficiency. Analysis of photosynthetic efficiency, enzymatic activity of antioxidant response system, level of pigments and L-proline concentration were performed to evaluate the HD effects. Results showed that HD altered some parameters related to photosynthetic activity, pigments accumulation, proline and enzymatic activity. Clone 433 of E. grandis presented higher response ability to HD. <![CDATA[<b>Foliar application of <i>Burkholderia</i> sp. strain TNAU-1 leads to activation of defense responses in chilli (<i>Capsicum annuum</i> L.)</b>]]> Induction of phenolics, peroxidase (PO), polyphenol oxidase (PPO), chitinase and thaumatin-like proteins (TLP) in leaves of chilli (Capsicum annuum L.) in response to foliar application with a biocontrol agent Burkholderia sp. strain TNAU-1 was studied. Chilli plants, when sprayed with Burkholderia sp. strain TNAU-1 showed increase in phenolic content one day after application and the maximum accumulation was observed seven days after treatment. Three new peroxidase isozymes (PO-1, PO-2 and PO-3) were induced in chilli leaves upon treatment with Burkholderia sp. strain TNAU-1. The activity of all the peroxidases was at the maximum level three days after treatment and subsequently decreased. Protein extracts obtained from Burkholderia sp. strain TNAU-1 treated plants exhibited a major polyphenol oxidase (PPO-1) one day after treatment. The activity of PPO-1 subsequently decreased, but continuously present throughout the experimental period of 15 days. Western blot analysis of protein extracts from Burkholderia sp. strain TNAU-1 treated chilli leaves revealed that two TLPs with sizes of 23 and 25 kDa and a chitinase with an apparent molecular weight of 28 kDa were induced three days after treatment. <![CDATA[<b>Effects of <i>in vitro</i> triacontanol on growth, antioxidant enzymes, and photosynthetic characteristics in <i>Arachis hypogaea</i> L.</b>]]> In vitro effects of triacontanol (TRIA) on antioxidant enzymes and photosynthetic characteristics were studied in Arachis hypogaea L. cultivars (M-13 and PBS24030). The in vitro impact of TRIA on multiplication potential was also evaluated, which was found to be best at 2.0 ml L-1 TRIA in combination with 6- Benzyl adenine (BA, 3 mg L-1) in both the groundnut cultivars. Rhizogenesis was observed in almost all the TRIA treated cultures in both the cultivars. Moreover, shoots failed to set roots, in the presence of BA. Total chlorophyll content, total soluble sugars, total soluble proteins and ascorbate peroxidase (APX; EC activity were found to be increasing with increasing concentrations of TRIA, whether alone or in combination with BA, however, genotypic differences were observed in case of Hill reaction activity (HRA) in between the cultivars. Best catalase (CAT; EC activity was reported at 1.0 ml L-1 TRIA with BA (3 mg L-1) in both the cultivars. Peroxidase (POX; EC and polyphenol oxidase (PPX; activity was maximum at 1.0 ml L-1 TRIA with BA (3 mg L-1) in M-13, whereas at 2.0 ml L-1 TRIA with BA (3 mg L-1) in PBS24030. Lipid peroxidation was found to be reduced with the supplementation of TRIA. The results obtained in the study clearly indicated not only the in vitro establishment of groundnut cultivars in the presence of TRIA but also its effect on various growth promontory physiological parameters. <![CDATA[<b>Thinning with NAA, NAD, ethephon, urea and by hand to improve fruit quality of 'Gerdi' apricot</b>]]> This research was conducted to study the effects of chemical and hand thinning on fruit quality of 'Gerdi' apricot. In the first year, three weeks after full bloom (AFB) branches of mature trees were sprayed with naphthalene acetic acid (NAA) at 10, 20, and 40 mg L-1, naphthalene acetamide (NAD) at 20, 40, and 80 mg L-1, ethephon at 50, 100 and 200 mg L-1, or urea at 0.2, 0.4, and 0.6%. In next year, hand thinning was performed as a separate experiment and leaf to fruit ratio (LFR) was adjusted to 10:1, 20:1 or 30:1 at pit-hardening stage of fruit development. In both years, NAA at 40 mg L-1, NAD at 80 mg L-1 and all concentrations of ethephon significantly increased fruit drop. All concentrations of urea significantly increased fruit drop in 2006, but only the two lower concentrations were effective in 2007. NAA at 20 and 40 mg L-1, and NAD at 40 and 80 mg L-1 increased fruit weight in 2006, but only the highest concentration of NAD was effective in 2007, while urea was effective at all concentrations in both years. Ethephon effect on fruit weight was not significant at all. Hand thinning consistently increased fruit weight, but length and diameter were increased only at a leaf to fruit ratio of 30:1. Hand thinning also increased total soluble solids (TSS), total soluble solids to total acidity ratio (TSS/TA), pit weight and flesh to pit ratio. <![CDATA[<b>Effect of Phytoaccumulation of Arsenic and Chromium on Structural and Ultrastructural Changes of Brake Fern (<i>Pteris vittata</i>)</b>]]> Structural and ultrastructural changes caused by bioaccumulation of As and Cr in brake fern (Pteris vittata), a known arsenic hyperaccumulator, were investigated. Potted plants of brake fern were exposed to metal treatments of As and Cr for three weeks. Leaf, stem and root samples were collected periodically and fixed for LM (Light Microscopy), SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) to evaluate anatomical changes. The fresh weights, dry weights, RWC (Relative Water Content) and plant heights were obtained before the brake fern plants were harvested for metal accumulation analysis. The As accumulated mainly in the shoots while Cr accumulated mainly in the roots of the metal-treated plants. Significant changes in the ferns physical characters, including fresh weight, dry weight, RWC, and plant height were observed for only Cr-treated plants but not for As-treated plants. Microscopic studies reveal the Cr accumulation resulted in dehydration and collapse of internal structure of leaves and cellular breakdown of roots. The As-treated plants showed no significant structural changes in leaves, stems and roots compared to control plants. Clotted depositions were observed in roots and stems of plant groups treated with highest concentration of Cr and As when compared to control (T0) group. Our study indicates that Cr has a profound impact on physiology and structure of fern plants. The accumulation of Cr resulted in decrease in growth rate, total biomass and RWC. We believe that brake fern plants can uptake, translocate and sequester As because it caused no significant structural changes in leaves, stems and roots of the plants. <![CDATA[<b>Relationship between photochemical efficiency (JIP-Test Parameters) and portable chlorophyll meter readings in papaya plants</b>]]> The Portable Chlorophyll Meter (PCM) is used to estimate the total chlorophyll and leaf nitrogen content of various species. Since there is a relationship between the chlorophyll concentration and the photochemical efficiency, a relationship can also be established between the PCM readings and some fluorescence variables to provide information on photosystem II (PSII) structure and activity. Papaya (Carica papaya L.) plants ['Sunrise Solo' (leaves with intense green coloring) and 'Golden' cultivars (leaves with yellow-green coloring) were grown in a greenhouse with 30% interception of photosynthetically active photon flux density. The plants were cultivated in 15L plastics pots. Ninety to 100 days after planting the older leaves turned yellow and the chlorophyll fluorescence variables and PCM readings were measured. At low PCM values (less than 30 to 'Sunrise Solo' and less than 20 to 'Golden') the PSII structure and activity were damaged, which is likely related to a reduction in the numbers of active reaction centers (RC/CS0). At higher PCM values the chlorophyll a fluorescence variables (ABS/RC, DI0/RC, TR0/CS0 e ET0/CS0) that are related to PSII structure and activity PSII were not responsive. These results indicated that the effects of chlorophyll content measured by PCM on the photochemical phase of photosynthesis evaluated by chlorophyll fluorescence occur after the degradation of chlorophyll molecules is initiated. In papaya the Portable Chlorophyll Meter (SPAD-502) was shown to be suitable for diagnosis of PSII energy distribution under N stress and senescence. <![CDATA[<b>Ecophysiological studies of two andean forest contrasting species <i>Abatia parviflora</i> and <i>Myrcianthes leucoxyla</i> under Bogotá conditions, Colombia</b>]]> The physiological response of high Andean forest contrasting plants, Myrcianthes leucoxyla, a shadow-facultative heliophyte, and Abatia parviflora, a heliophyte, was studied during the transition from dry season to wet season in Bogotá. Light response curves (A-PAR), water potential (Ψw), transpiration rate (E), stomatal conductance (gs), leaf soluble protein content and peroxidase activity were measured in this study in a 48h cycle. The values for E, gs, Ψw and Ψw predawn for M. leucoxyla were 0.07 to 4.89 µg/cm s, 0.02 to 0.5 cm s-1, -0.025 to -1.05 MPa, and-0.1 MPa, respectively. For A. parviflora E, gs, Ψw and Ψw predawn were 0.47 to 12.27 µg/cm s, 0.17 to 1.42 cm s-1, -0.05 to -0.3 MPa and -0.075 MPa, respectively. A. parviflora presented a tendency of stomatal closure at midday and peroxidase activity increased with the increasing solar radiation, this did not occur in M. leucoxyla. The light compensation point (Ic) in A. parviflora was about 18.10 µmol photon m-2s-1, typical for a heliophyte plant; while for M. leucoxyla it was 8.87 µmol photon m-2s-1, slightly above the maximal reported values for shadow plants and under the minimal reported values for light plants. The lowest photosynthetic rate (A) of M. leucoxyla (2.8 µmol CO2 m-2s-1) in comparison with A. parviflora (7.4 µmol CO2 m-2s-1) is compensated with a better photonic use efficiency (± 0.7792 mol C mol-1). <![CDATA[<b>Oleoresin yield of <i>Pinus elliottii</i> Engelm seedlings</b>]]> Pinus elliottii is a fast-growing conifer well adapted to southern Brazil, used for wood fiber and resin production. Oleoresin production is part of the plant's defense systems and is induced by ethylene, which production is stimulated by hypoxic conditions. The experiment was designed with the goal of verifying whether one year-old plants had measurable oleoresin yield and if flooding led to increased oleoresin production. There was an increase of 78% in oleoresin production after 14 to 21 days of flooding and plants with larger stem diameters were more productive.<hr/>Pinus elliottii é uma conífera de rápido crescimento usada para produção de fibras de madeira e para resinas no sul do Brasil. A produção de oleoresinas é parte do sistema de defesas da planta e é regulada por etileno, cuja a produção é estimulada em condições de hipoxia. Com os objetivos de verificar se as plantas com cerca de um ano já produziam níveis mensuráveis de resinas e se estes respondiam ao alagamento é que esse estudo foi realizado. Houve um aumento de até 78% de produção de resina entre 14 e 21 dias após o alagamento induzido e, plantas com maior diâmetro de caule foram as mais produtivas.