*Autor para correspondência: valeri@fcav.unesp.br RESUMO: O objetivo deste trabalho foi avaliar o crescimento, as alterações morfológicas e a composição mineral de plantas de pau-brasil (Caesalpinia echinata) decorrentes da omissão de nutrientes pela técnica do elemento faltante em experimento em casa de vegetação. O delineamento experimental foi inteiramente casualizado, com 12 tratamentos: testemunha (solo natural), completo (N, P, K, Ca, Mg, S, B, Cu, Mn e Zn), e adubação com omissão de cada um dos nutrientes do tratamento completo e cinco repetições. Cada parcela foi constituída por uma planta em vaso contendo 7 dm 3 de Neossolo Quartzarênico. Foram avaliados sintomas visuais de deficiência nutricional, altura, diâmetro do caule, matéria seca da parte aérea das plantas, incluindo caule, ramos e folhas e teor dos nutrientes nas folhas. A omissão de nitrogênio em Neossolo Quartzarênico limitou o crescimento em altura e a produção de biomassa da parte aérea das plantas de pau-brasil. Os primeiros sintomas de deficiência nutricional foram decorrentes da omissão de N, em seguida apareceram os sintomas de P, Ca, Mg, S, Cu e Mn e, mais tardiamente, os sintomas da deficiência de K e B. Para cada nutriente, houve diferença entre as médias de teores nas folhas em função dos tratamentos.Palavras chave: pau-brasil, deficiência nutricional, diagnose, nutrição florestal. EFFECTS OF NUTRIENT OMISSION IN Caesalpinia echinata PLANTS ABSTRACT: The objective of this study was to evaluate the growth, the morphological alterations and the mineral composition of brazilwood (Caesalpinia echinata) plants caused by mineral nutrients omission in a green house experiment. The experimental unitswere distributed in the green house according to a completely random design. The treatments, each repeated five times, were the following : check (natural soil), complete (N, P, K, Ca, Mg, S, B, Cu, Mn, and Zn)
Tomato production is influenced by shoot branching, which is controlled by different hormones. Here we produced tomato plants overexpressing the cytokinin-deactivating gene CYTOKININ OXYDASE 2 (CKX2). CKX2-overexpressing (CKX2-OE) plants showed an excessive growth of axillary shoots, the opposite phenotype expected for plants with reduced cytokinin content, as evidenced by LC-MS analysis and ARR5-GUS staining. The TCP transcription factor SlBRC1b was downregulated in the axillary buds of CKX2-OE and its excessive branching was dependent on a functional version of the GRAS-family gene LATERAL SUPPRESSOR (LS). Grafting experiments indicated that increased branching in CKX2-OE plants is unlikely to be mediated by root-derived signals. Crossing CKX2-OE plants with transgenic antisense plants for the strigolactone biosynthesis gene CAROTENOID CLEAVAGE DIOXYGENASE (CCD7-AS) produced an additive phenotype, indicating independent effects of cytokinin and strigolactones on increased branching. On the other hand, CKX2-OE plants showed reduced polar auxin transport and their bud outgrowth was reduced when combined with auxin mutants. Accordingly, CKX2-OE basal buds did not respond to auxin applied in the decapitated apex. Our results suggest that tomato shoot branching depends on a fine-tuning of different hormonal balances and that perturbations in the auxin status could compensate for the reduced cytokinin levels in CKX2-OE plants.
Integrated signaling network involving abscisic acid (ABA), nitric oxide (NO), and indoleacetic acid (IAA) controls root morphogenesis during salt stress by a mechanism still poorly understood. The present data unveiled an ABA-NO-IAA interaction underlying radicular morphological responses to salinity. Three Solanum lycopersicum genotypes were analyzed: wild type, ABA-insensitive mutant (sitiens), and auxin-responsive (DR5::GUS) plants. Nitric oxide fluorescence, nitrate reductase activity, auxin signaling, and some molecular analyses were performed. Pharmacological inhibitors and NO donor sodium nitroprusside were also used to evaluate NaCl-induced root morphological responses. Sodium nitroprusside inhibited primary root length, increased lateral root emergence, and rescued salt inhibited lateral root growth. The results showed that NO integrates the ABA-IAA signaling network of root system responses under salt stress, involving: (a) ABA and molybdenum-dependent enzymes as responsible for saltinduced NO production; (b) modulations of the plasma membrane H ?-ATPase coupling and isoforms differential expression; and (c) ABA-mediated and NOdependent antioxidative enzymes activities.
ABSTRACT:The objective of this work was to evaluate the effects of potassium and soil moisture levels on the growth of Corymbia citriodora plants. Four doses of potassium were applied (0, 40, 80 and 120 mg . dm -3 ) and three soil moisture levels were established (50-80%, 65-80% and 80% of maximum soil field capacity). The experiment was a 4 x 3 factorial arrangement of treatments within a randomized complete design with six replications for each treatment and one pot with two plants for each plot. At 90 days after planting, the plant growth parameters: survival rate, height, stem diameter, leaf area, relative chlorophyll concentration, leaf dry mass, stem and branches dry mass, root dry mass, total dry mass and leaf macronutrient contents were measured. High soil moisture content is necessary for Corymbia citriodora seedlings at nursery stage. Effects of the K doses were not observed in plants, even when they were cultivated in a soil with a low content of this nutrient. EFEITOS DA APLICAÇÃO DE POTÁSSIO E UMIDADES DO SOLO NO CRESCIMENTO DE PLANTAS DE Corymbia citriodora RESUMO:Conduziu-se este trabalho, com o objetivo de avaliar os efeitos de doses de potássio e umidades do solo no crescimento de plantas de Corymbia citriodora. Foram aplicadas quatro doses de potássio (0, 40, 80, e 120 mg . dm -3 ) e promovidas três níveis de umidades do solo (50-80%, 65-80% e 80% do volume máximo de água retido pelo solo em vaso), combinadas em um esquema fatorial 4x3. O delineamento experimental foi inteiramente casualizado com seis repetições, e cada parcela foi composta por um vaso contendo duas plantas. Aos 90 dias após o plantio, foram avaliados: porcentagem de sobrevivência, altura, diâmetro do caule, área foliar, teor relativo de clorofila, massa de matéria seca de folhas, de caule e ramos, de raízes e total, e teor de macronutrientes nas folhas. Mudas de Corymbia citriodora necessitam de alta umidade do solo na fase de viveiro. Não foram observados efeitos das doses de potássio nas plantas, mesmo quando a concentração desse nutriente no solo era baixa.
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