RESUMO

Plant species of the Brazilian Caatinga experience seasonal wet and dry extremes, requiring seasonally different leaf characteristics for optimizing water availability. We investigated if Croton blanchetianus Baill exhibits leaf morphoanatomical traits across seasons and positioning in sunlight/natural shade. Leaves of ten 1-3 m tall plants in full sunlight and ten in natural shade were assessed in May, July (wet season), October and December (dry season) 2015 for gas exchange, leaf size, lamina and midrib cross sections (14 parameters), and chloroplast structure (5 parameters). Net photosynthesis was greater during the wet season (21.6 µm-2 s-1) compared to the dry season (5.8 µm-2 s-1) and was strongly correlated with almost all measured parameters (p < 0.01). Shaded leaves in the wet season had higher specific leaf area (19.9 m2 kg-1 in full-sun and 23.1 m2 kg-1 in shade), but in the dry season they did not differ from those in full sun (7.5 m2 kg-1 and 7.2 m2 kg-1). In the wet season, the expansion of the adaxial epidermis and mesophyll lead to larger and thicker photosynthetic area of leaves. Furthermore, chloroplast thickness, length and area were also significantly larger in full sunlight (2.1 µm, 5.1 µm, 15.2 µm2; respectively) and shaded plants (2.0 µm, 5.2 µm, 14.8 µm2; respectively) during wetter months. Croton blanchetianus exhibits seasonal plasticity in leaf structure, presumably to optimize water use efficiency during seasons of water abundance and deficit. These results suggest that the species is adaptable to the increased drought stress projected by climate change scenarios.

Assuntos

RESUMO

The emission profile of volatile organic compounds (VOCs) and nitric oxide (NO) in young and mature leaves of Croton floribundus was assessed in plants exposed to filtered air (FA) and ozone-enriched filtered air (FA+O3). After the period of exposure, leaves were enclosed in polyethylene terephthalate bags and VOCs were collected in young and mature leaves. Both young and mature leaves constitutively emitted the same VOC, but the concentrations were higher in young leaves. O3 exposure induced the emission of sesquiterpenes (mainly ß-caryophyllene) known as antioxidant compounds that may scavenge O3. Young leaves were the highest emitters of sesquiterpenes. O3 induced a rapid accumulation of NO in different tissues and leaf developmental stages; this accumulation was marked in palisade and spongy parenchyma cells in young and mature leaves, respectively. O3 altered the levels of the signaling compound methyl salicylate (MeSA). Moreover, our data showed that NO together with VOC emissions, such as geranyl acetate, α-cadiene, trans-farnesol, cis-ß-farnesene, and MeSA, participate of plant defense mechanisms against the oxidative damage caused by O3.

Assuntos

RESUMO

O presente estudo teve como principal objetivo avaliar o potencial de atividade antimicrobiana de diterpeno isolado de Croton antisyphiliticus, espécie nativa do Cerrado, frente biofilme de Staphylococcus aureus, isolados do leite de animais com mastite. O diterpeno ácido ent-kaur-16-en-18-óico foi avaliado quanto à capacidade de erradicação da biomassa e também à redução da população bacteriana sob o biofilme. O antibiótico sulfato de gentamicina foi utilizado como tratamento comparativo. A atividade antibiofilme foi determinada por meio dos métodos do Cristal Violeta e da Contagem de Unidades Formadoras de Colônia. Os resultados obtidos demonstraram que o ácido ent-kaur-16-en-18- óico, na concentração de 250 µg/mL, reduziu 56% da biomassa formada, enquanto a gentamicina, na concentração de 30 mg/mL, apenas 13%. Quanto à atividade nas células bacterianas sob o biofilme, não houve diferença estatística significativa entre os tratamentos, que minimizaram cerca de 3 logs da população de S. aureus. Portanto, nas condições ensaiadas, o diterpeno ent-kaur-16-en-18-óico destacou-se por apresentar atividade antibiofilme significativa contra S. aureus, em concentração 120 vezes menor quando comparado ao antibiótico gentamicina.(AU)

The present study aimed to evaluate the potential antimicrobial activity of diterpene isolated from Croton antisyphiliticus, native species of the Cerrado, against biofilm of Staphylococcus aureus isolated from milk from animals with mastitis. The diterpene ent-Kaur-16-on-18-oic acid were evaluated for their ability to eradicate biomass and also reducing the bacterial population in the biofilm. The antibiotic gentamicin was used as a comparative treatment. Antibiofilm activity was determined by the methods of Crystal Violet and Count of Colony Forming Units. The results demonstrated that the ent-Kaur-16-on-18-oic acid, at a concentration of 250 μg/mL, reduced 56% of the biomass formed, while gentamicin, at a concentration of 30 mg/ml, only 13%. Regarding the activity in bacterial cells in the biofilm, there was no statistically significant difference between treatments, that minimized about 3 logs of the population of S.aureus. Therefore, in the conditions tested, the diterpene ent-kaur-16-on-18-oic highlighted for presenting antibiofilm significant activity against S. aureus, at a concentration 120 times lower when compared to the gentamicin antibiotic.(AU)

Assuntos

RESUMO

O presente estudo teve como principal objetivo avaliar o potencial de atividade antimicrobiana de diterpeno isolado de Croton antisyphiliticus, espécie nativa do Cerrado, frente biofilme de Staphylococcus aureus, isolados do leite de animais com mastite. O diterpeno ácido ent-kaur-16-en-18-óico foi avaliado quanto à capacidade de erradicação da biomassa e também à redução da população bacteriana sob o biofilme. O antibiótico sulfato de gentamicina foi utilizado como tratamento comparativo. A atividade antibiofilme foi determinada por meio dos métodos do Cristal Violeta e da Contagem de Unidades Formadoras de Colônia. Os resultados obtidos demonstraram que o ácido ent-kaur-16-en-18- óico, na concentração de 250 µg/mL, reduziu 56% da biomassa formada, enquanto a gentamicina, na concentração de 30 mg/mL, apenas 13%. Quanto à atividade nas células bacterianas sob o biofilme, não houve diferença estatística significativa entre os tratamentos, que minimizaram cerca de 3 logs da população de S. aureus. Portanto, nas condições ensaiadas, o diterpeno ent-kaur-16-en-18-óico destacou-se por apresentar atividade antibiofilme significativa contra S. aureus, em concentração 120 vezes menor quando comparado ao antibiótico gentamicina.

The present study aimed to evaluate the potential antimicrobial activity of diterpene isolated from Croton antisyphiliticus, native species of the Cerrado, against biofilm of Staphylococcus aureus isolated from milk from animals with mastitis. The diterpene ent-Kaur-16-on-18-oic acid were evaluated for their ability to eradicate biomass and also reducing the bacterial population in the biofilm. The antibiotic gentamicin was used as a comparative treatment. Antibiofilm activity was determined by the methods of Crystal Violet and Count of Colony Forming Units. The results demonstrated that the ent-Kaur-16-on-18-oic acid, at a concentration of 250 μg/mL, reduced 56% of the biomass formed, while gentamicin, at a concentration of 30 mg/ml, only 13%. Regarding the activity in bacterial cells in the biofilm, there was no statistically significant difference between treatments, that minimized about 3 logs of the population of S.aureus. Therefore, in the conditions tested, the diterpene ent-kaur-16-on-18-oic highlighted for presenting antibiofilm significant activity against S. aureus, at a concentration 120 times lower when compared to the gentamicin antibiotic.

Assuntos

RESUMO

The present work evaluated the germinability and vigor of Croton urucurana seeds. 1) Seeds were sorted by color (caramel, gray and black) and were subjected to seven different pre-germination treatments followed by incubation at 20ºC, 25°C or 20/30°C. 2) Seeds were stored in cold chambers or at room temperature for up to 300 days and were subsequently incubated at 20/30ºC in a germination chamber or under greenhouse conditions. Only gray seeds showed significant germination rates. The highest first count percentages of total germination and the highest germination speed indices were observed in control seeds and in those which were treated with water or 200 mg.L(-1) gibberellic acid for 12 hours. Seeds stored under refrigeration showed the highest values for all of the characteristics examined, as well as less electrical conductivity of the imbibing solution. Seedlings were more vigorous when seeds were stored for 300 days in a cold chamber. The seedlings production can be increased by incubating the seeds at alternating temperatures (20/30°C). The seeds do not need pre-germination treatments.

Assuntos

RESUMO

Codiaeum variegatum (L) Blume cv. "Corazon de oro" and cv. "Norma" are successfully micropropagated when culture are initiated with explants taken from newly sprouted shoots. The establishment and multiplication steps are possible when 1 mg/L BA or 1 mg/L IAA and 3 mg/L 2iP are added to MS medium, according to the cultivar respectively selected.Adventive organogenesis and somatic embryogenesis are induced from leaf explants taken from in vitro buds of croton. On leaf-sectioned of "Corazon de oro" cultured in vitro, 1 mg/L BA stimulates continuous somatic embryos development and induces some shoots too. Replacing BA with 1 mg/L TDZ induces up to 100% bud regeneration in the same explants. On the other hand, leaf-sectioned of C. variegatum cv. Norma does not start somatic embryo differentiation if 1 mg/L TDZ is not added to the MS basal medium. Incipient callus is observed after 30 days of culture, and then, subculture to MS with 1 mg/L BA allows the same process to show on the "Corazon de oro" cultivar. Somatic embryos show growth arrest that is partially overcome by transfer to hormone-free basal medium with activated charcoal. Root induction is possible on basal medium plus 1 mg/L IBA. Plantlets in the greenhouse have variegated leaves true-to-type.

Assuntos