Aspectos eco-fisiológicos limitantes da regeneração natural

Natural regeneration comprises the initial stages of establishment and development, and is considered a slow and unpredictable process, due to the complex interaction between the successful establishment of seedlings and different environmental factors. Thus, the aim of this study was show a review addressing eco-physiological factors influencing the natural regeneration of forests as reserves of seed, production and seed dispersal, germination and dormancy, temperature, and water availability and light. Knowledge of the effect of these factors and their interactions with the community are essential to forest management, regarding its management and revegetation of disturbed areas. Thus, simulations of regeneration constitute naturally a very useful tool.A regeneração de florestas compreende as etapas iniciais de estabelecimento e desenvolvimento, sendo considerada um processo lento e imprevisível, devido à complexa interação entre o sucesso no estabelecimento de plântulas e os fatores ambientais. Desse modo, esse trabalho teve como objetivo apresentar uma revisão bibliográfica abordando aspectos ecofisiológicos que influenciam a regeneração natural de florestas, como reserva da semente, produção e dispersão de sementes, dormência e germinação, temperatura, e disponibilidade de água e luz. O conhecimento do efeito desses fatores e suas interações com a comunidade são essenciais para a gestão das florestas, no que tange o seu manejo e a revegetação de áreas alteradas. Nesse sentido, simulações de regeneração constituem, naturalmente, uma ferramenta muito útil

Physiology and morphology of rice plants with silicon supplementation and Dietholate seed treatment under water deficit

Silicon is an enzyme stimulator that promotes signaling for the production of antioxidant, osmoprotective compounds and attenuates interference in photosynthesis in rice plants subjected to water deficit. The aim of this study was to evaluate the possible effects of silicon as a stress reliever in rice plants grown from seeds treated with dietholate under of water deficit conditions. The experimental design was fully randomized with three replicates, 144 experimental units consisting of pots containing 4.4 pounds soil, and a 3x2x2x4 factorial arrangement: three soil water conditions (50% and 100% of soil water retention capacity and water blade of 5.0 cm); two cultivars (IRGA 424 RI and Guri INTA CL); two sources of Si (sodium and potassium metasilicate); and four Si rates (0; 4.0; 8.0 and 16 g L-1). Silicon boosted stomatal density; induced an increase in the maximum photochemical efficiency of photosystem II (PSII) under both water deficit and optimal conditions, boosting photosynthesis; and increased effective quantum yield of PSII and levels of total dry mass. Thus, silicon attenuated the effects of water deficit in plants grown from seeds treated with dietholate

SUBSTRATE AND FERTILIZATION IN THE QUALITY OF Myrocarpus frondosus SEEDLINGS

 Myrocarpus frondosus is a native species with high commercial timber value. Thus, the objective of this research was to evaluate the quality of seedlings of Myrocarpus frondosus in the nursery and to indicate the most adequate substrate and fertilization for the production of seedlings. The experiment was conducted in a completely randomized design, with four replications, in a factorial scheme, composed of four combinations of substrates: S1-100% commercial substrate (CS); S2 - 80% CS and 20% carbonated rice husk (CRH); S3 - 60% CS and 40% CRH; S4 - 40% CS and 60% CRH, and four fertilizations: NF – No fertilization; CRF – controlled release fertilizer (ammonium sulfate, simple superphosphate and potassium chloride); RRF – ready release fertilizer and micronutrients. Physical and chemical analyses were performed on the substrate. At 300 days after emergence, the following morphological variables were evaluated: (height, stem diameter, H/SD ratio, leaf area, root length, aerial dry mass, root dry mass, total dry mass, Dickson quality index) and the physiological variables chlorophyll a, chlorophyll b, carotenoids, initial fluorescence, maximum fluorescence, Fv/Fm ratio and electron transport rate). Regardless of the substrate and fertilization, slow growth of the species was observed, even for the best treatment, which was verified from the height (17.87 cm) and stem diameter (2.62 mm). The use of the commercial substrate (40%) with carbonated rice husk (60%) associated with the concentration of 6 g L-1 of controlled release fertilizer is recommended, since they present the best results for the morphological and physiological variables in the nursery in general

DIFFERENT SHADING INTENSITIES INTERFERE WITH THE GROWTH OF Myrocarpus frondosus ALLEMÃO SEEDLINGS IN THE NURSERY?

Native tree species present different responses depending on their adaptability to varying degrees of sunlight. The objective of this study was to evaluate the growth of Myrocarpus frondosus seedlings under different shade conditions in a nursery. The experimental design included randomized blocks in a factorial scheme, corresponding to treatments of full sun (0%), or one of three shading intensities (30%, 50%, and 70%), with evaluation times of 30, 90, 150, 210, 270, 330, and 390 days after emergence – d.a.e. The evaluation of the morphological attributes height (H) and stem diameter (SD) were determined every 60 days, and H/SD ratio were calculated. At 390 d.a.e, the following attributes were evaluated: aerial dry matter, (ADM), root dry matter (RDM), total dry matter, (TDM), Dickson quality index (DQI), leaf area (LA), root volume (RV), and root length. The pigment contents of chlorophyll a, chlorophyll b, and chlorophyll a/b ratio were also identified, along with carotenoid content, maximum quantum yield PSII (Fv/Fm), and electron transport rate (ETR). Myrocarpus frondosus requires shading in its initial stage of growth, at an ideal intensity of 50% or 70% for producing seedlings.

GROWTH AND PHYSIOLOGICAL ATTRIBUTES OF Cordia trichotoma SEEDLINGS IN RESPONSE TO FERTILIZATION WITH PHOSPHORUS AND POTASSIUM

The cultivation of native tree species of economic and environmental interest, such as Cordia trichotoma, still depends on nutritional information. This study aimed to identify the effect of phosphorus (P) and potassium (K) application on the growth and photosynthetic activity of seedlings of Cordia trichotoma. In a greenhouse, ten treatments were tested considering three levels of P (150, 300, and 450 mg dm-3 ), three of K (50, 100, and 150 mg dm-3 ) and a control sample (with no fertilization). Pots filled with Red Argisol were used. At 180 days after prick, the following variables were evaluated: shoot height, stem diameter, area dry matter, root dry weight, leaf area, chlorophyll a fluorescence and photosynthetic pigments. The supplementation with P and K promoted increased growth and photosynthetic capacity of the seedlings. The treatment with 450 mg dm-3 of P and 50 mg dm-3 of K provided the highest growth and the best use of the light energy by the photosystem II (Fv/Fm = 0.76), as well as lower energy loss index (Fo = 172.5). It is recommended the application of 450 mg dm-3 of P and 50 mg dm-3 of K, with the aim at higher growth and photosynthetic rate of seedlings of C. trichotomaThe cultivation of native tree species of economic and environmental interest, such as Cordia trichotoma, still depends on nutritional information. This study aimed to identify the effect of phosphorus (P) and potassium (K) application on the growth and photosynthetic activity of seedlings of Cordia trichotoma. In a greenhouse, ten treatments were tested considering three levels of P (150, 300, and 450 mg dm-3), three of K (50, 100, and 150 mg dm-3) and a control sample (with no fertilization). Pots filled with Red Argisol were used. At 180 days after prick, the following variables were evaluated: shoot height, stem diameter, area dry matter, root dry weight, leaf area, chlorophyll a fluorescence and photosynthetic pigments. The supplementation with P and K promoted increased growth and photosynthetic capacity of the seedlings. The treatment with 450 mg dm-3 of P and 50 mg dm-3 of K provided the highest growth and the best use of the light energy by the photosystem II (Fv/Fm = 0.76), as well as lower energy loss index (Fo = 172.5). It is recommended the application of 450 mg dm-3 of P and 50 mg dm-3 of K, with the aim at higher growth and photosynthetic rate of seedlings of C. trichotoma

Tolerance of cultivars and clonal selections of peach rootstocks to excess aluminum

Forms of aluminum (Al) present in the solution of tropical and subtropical soils can cause toxicity in rootstocks and peach cultivars, impairing growth and productivity. This can be minimized by growing Al-tolerant rootstocks and cultivars. However, this is not sufficiently known, especially because plant breeding programs do not always consider tolerance as a selection variable for genetic materials. The study aimed to (a) select cultivars and clonal selections of Al-tolerant peach rootstocks, (b) identify variables that confer Al tolerance for use in genetic improvement programs, and (c) propose critical levels (NC) and ranges of toxicity (TF) of Al in relation to morphological variables of the root system. The experimental design was completely randomized, comprising a factorial of 13 (cultivars and clonal selections) x 2 (with and without Al) with three replications. Own-rooted ‘BRS Mandinho’ peach seedlings (without rootstock) and grafted seedlings of ‘BRS Mandinho’ on different cultivars and clonal rootstock selections were cultivated in a hydroponic system, composing two levels for the Al factor (absence and presence at 100 mg L−1). The morphological variables of the canopy and root system, Al accumulation in tissues, translocation factor, and the critical level (NC) and toxicity range (TF) of Al in the roots were evaluated. Rootstocks FB-SM-09-43, JB-ESM-09-13, SAS-SAU-09-71, SS-CHI-09-40, ‘Sharpe’ and VEH-GRA-09-55 were tolerant at high Al concentrations. The NC of Al in the roots in relation to the root surface area of peach rootstocks was 1400 mg Al kg−1, and the FT was between 1200 and 1500 mg Al kg−1

Ameliorate the cadmium toxicity in Solanum tuberosum L. plants with selenium and silicon application

The present study aimed to prove the efficiency of Se or Si as relievers of the Cd toxicity in potato plants. Solanum tuberosum plants, Asterix genotype, from in vitro propagation were placed in pots with sand and irrigated with complete nutrient solution for 60 days under six treatments: T1: Control (nutrient solution); T2: 2.5 µM Se; T3: 2.5 mM Si; T4: 50 µM Cd; T5: 50 µM Cd + 2.5 µM Se; T6: 50µM Cd + 2.5 mM Si. The treatments were arranged in completely randomized design, with four replicates for each treatment and six plants per replicate. The plants were collected at 30 and 60 days after application of the treatments. Cadmium was highly toxic in all parameters (dry and fresh weight, plant height, leaf number, leaf area, root and photosynthetic parameters), in both assessments. However, Se and Si were effective in mitigating Cd toxicity in all parameters, although Si has been shown to be more efficient than Se in dry weight and plant height parameters. Thus, from data obtained in this study, it is clear that the beneficial elements tested have power to ameliorate Cd toxicity

Growth of potato genotypes under different silicon concentrations

The aim of this work was to verify the beneficial potential of Siliconon the growth of potato genotypes in order to select potato genotypes that best respond to Si application. Four potato genotypes were used: SMIJ319-7, Dakota Rose, SMIF212-3 and SMINIA793101, grown in hydroponic system. The plants were transferred to nutrient solutions with four Si concentrations: 0; 0.5; 2.5; and 5.0 mM as NaSiO3. After seven days of exposure to treatments, leaf area, leaf number, shoot length, and fresh and dry weight of roots, stem and leaves were determined. The application of 0.5 mM Si promoted an increase in growth parameters of plants used in this work, mainly in leaf area, leaf number,and leaf and stem dry weight. However, the application of higher concentrations of Si (2.5 mM) promoted reduction in the growth parameters, mainly in leaf area. It was also possible to observe a genotypic variation with respect to Si, SMIJ319-7 and SMIF212-3 genotypes being the most responsive to Si. Therefore, the concentration of 0.5 mM Si is considered optimal for potentiating the growth of potato plants, and SMIJ319-7 and SMIF212-3 genotypes are the most responsive to Si

Efeito do alumínio sobre variáveis morfofisiológicas e bioquímicas de Handroanthus heptaphyllus (Vell.) Mattos em sistema hidropônico / Effect of aluminum on morphophysiological and biochemical variables of Handroanthus heptaphyllus (Vell.) Mattos in hydroponic system

O alumínio (Al) é o terceiro elemento mais presente na crosta terrestre, e quando solubilizado e em contado com as plantas, pode prejudicar o crescimento e o desenvolvimento das mesmas. Sendo assim, o objetivo deste trabalho foi avaliar o comportamento morfofisiológico e bioquímico de plantas de ipê-roxo (Handroanthus heptaphyllus) expostas a concentrações de Al em solução nutritiva. Foram propagadas e selecionadas mudas homogêneas entre 7 e 13 cm, sendo que essas foram encaminhadas para sistema hidropônico contendo solução nutritiva (sem P e pH 4,5 ± 0,1), e expostas a cinco concentrações de Al (0, 25, 50, 75 e 100 mg L-1). Utilizou-se delineamento inteiramente casualizado, sendo 10 plantas por tratamento. Após 14 dias de exposição aos tratamentos, determinou-se o número de folíolos, a altura de plantas, o comprimento das raízes, a área foliar e radicular, a massa fresca e seca das folhas, caule e raízes, o conteúdo de clorofilas a, b, totais e carotenoides, a atividade da enzima superóxido dismutase (SOD), a peroxidação lipídica de membrana e o conteúdo de peroxido de hidrogênio. Os dados foram submetidos à análise de variância e as médias comparadas pelo Teste de Tukey a 5% de probabilidade de erro. Nas variáveis morfofisiológicas, a espécie mostrou-se tolerante ao Al, onde seu sistema radicular sofreu com a presença do Al, mas as plantas não apresentaram qualquer tipo de efeito em variáveis como teor de massa fresca e seca, incremento em altura e número de folíolos, área foliar e radicular e parâmetros fotossintéticos. Além disso, o Al não promoveu a redução nos teores de clorofilas. As plantas sofreram estresse oxidativo na presença de Al, segundo resultados da peroxidação lipídica, entretanto o resultado da superóxido dismutase e do peróxido de hidrogênio não diferiram entre os tratamentos. Conclui-se então que a H. heptaphyllus é uma espécie com capacidade para tolerar altas concentrações de Al, podendo ser plantada em solos ácidos, podendo ser uma opção para o restabelecimento vegetal em solos ácidos e áreas contaminadas com metais

Germinação, crescimento inicial e estresse oxidativo em plântulas de Luehea divaricata Martius et Zuccarini cultivadas in vitro com alumínio / Germination, initial growth and oxidative stress in Luehea divaricata Martius et Zuccarini seedlings cultivated in vitro with aluminum

O objetivo deste estudo foi verificar o efeito do alumínio (Al) sobre a germinação, crescimento inicial e estresse oxidativo de plântulas de Luehea divaricata em cultivo in vitro. Sementes de L. divaricata foram inoculadas em tubos de ensaio contendo meio MS com diferentes concentrações de Al (0, 50 e 100 mg L-1), em pH 4,5. As plântulas foram cultivadas em sala de crescimento, em delineamento inteiramente casualizado, com quatro repetições de 20 tubos de ensaio cada, e uma semente por tubo. Após 60 dias de cultivo, as plântulas foram coletadas para as análises morfológicas e bioquímicas. A germinação de sementes e a biomassa fresca e seca de parte aérea foram significativamente reduzidas pelo Al. O número de folhas, comprimento da raiz principal, altura, massa fresca de raízes, diâmetro e volume médio radicular foram reduzidos em 100 mg L-1 de Al. O comprimento médio de raízes, a área superficial e biomassa seca de raízes não foram afetados pelo Al. Nas raízes, a concentração de 100 mg L-1 reduziu a atividade da guaiacol peroxidase (POD) e aumentou a da superóxido dismutase (SOD), enquanto na parte aérea essas enzimas foram inibidas pelo Al, mas o aumento na peroxidação lipídica só foi observado em 100 mg L-1. Com base nos resultados, pode-se concluir que as plântulas de L. divaricata apresentam tolerância ao Al em concentração de até 50 mg L-1 quando presente no meio de crescimento in vitro. Esta é uma informação relevante para utilização desta espécie no reflorestamento e descontaminação de solos ácidos