Alexandre Bosco de Oliveira

Comparison Between the Water and Salt Stress Effects on Plant Growth and Development

Abiotic stress limits crop productivity [1], and plays a major role in determining the distri‐ bution of plant species across different types of environments. Abiotic stress and its effects on plants in both natural and agricultural settings is a topic that is receiving increasing at‐ tention because of the potential impacts of climate change on rainfall patterns and tempera‐ ture extremes, salinization of agricultural lands by irrigation, and the overall need to maintain or increase agricultural productivity on marginal lands. In the field, a plant may experience several distinct abiotic stresses either concurrently or at different times through the growing season [2].

Effects of osmoconditioning on the germination and vigor of sorghum seeds with different physiological qualities.

The objective of this study was to evaluate the effect of osmotic conditioning on the germination and vigor of sorghum seeds with different physiological qualities from the IPA 1011 cultivar. The experimental design was completely randomized with four replications in a factorial 2 x 2, consisting of four treatments: 1. aged seeds, 2. seed not aged, 3. seeds aged and conditioned osmotically and 4. seeds not aged and conditioned osmotically. The seeds quality was evaluated from the water content (WC), mass of thousand seeds (MTS), the first germination count (FGC) standart germination test (SGT), germination speed index (GSI), germination mean time (GMT ), accelerated aging test (AAT), cold test (CT), electrical conductivity test (ECT) and leaching of potassium test (LPT). The results showed that artificial aging negatively affects the performance of sorghum seeds and such effects can be partially reversed by priming. This technique does not influence germination but further benefits vigor in physiologically superior and inferior seeds.

Emergency of Copernicia Hospita Martius seedlings depending on the size seed, of the substrate and environment

The slow and desuniforme germination seeds of palm trees brings problems in the propagation of the species belonging to this family, more difficult, primarily, the production of seedlings on a commercial scale. This work objective was to determine the effect of the size seed, substrates and the environment in emergency of Copernicia hospita Martius seedlings. Seeds were referred to treatments: substrates [(red sand + carnauba straw + humus (2,5:2,5:1 by volume) and soil + dark sand + organic compound Polefertil® (2:2:1 by volume)]; environments (sun and house of vegetation), and size seed (small, medium, large and mix). The treatments were compared in terms of emergency percentage, estimated to 60 days after sowing, speed emergency index and mean emergency time. The factors examined not affect the emergency percentage seedlings. Seeds of C. hospita mixing and small size, sown in both substrates, under house of vegetation, provide emergency fastest of the seedlings.

Seed priming effects on growth, lipid peroxidation, and activity of ROS scavenging enzymes in NaCl-stressed sorghum seedlings from aged seeds

Abstract The aim of this study was to evaluate growth, lipid peroxidation, and activity of antioxidative enzymes in sorghum seedlings grown under salt stress from artificially aged and primed seeds. The experimental design was completely randomized, with four replications per treatment, in a 2×2×2 factorial arrangement that consisted of eight treatments: two seed vigor levels (aged or not), two seed types (primed or not), and two salinity levels (0 and 100 mM NaCl). In low physiological quality (aged) seeds, the osmoconditioning mitigated the salinity negative effects (NaCl at 100 mM) on seedling growth. The results suggest that osmoconditioning induced an increase in catalase (CAT) and guaiacol peroxidase (POX) activities and these enzymes protected the seedlings against oxidative damage caused by seed accelerated aging and salinity in nutrient solutions. Finally, the observed behavior for superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities suggest that changes in these enzymes in both shoot and roots could do not be induced by studied treatments, because the changes in these organs are unrelated to each other.

Accumulation of organic and inorganic solutes in NaCl-stressed sorghum seedlings from aged and primed seeds

Although it has been known that the seeds physiological potential affects its response to osmoconditioning and abiotic stresses, researches involving seed aging and priming associated to abiotic stresses are scarce. The aim of this work was to evaluate the role of seed priming on salt tolerance in sorghum seedlings from seeds with two vigor levels (aged or non-aged) and to verify the organic and inorganic solute contributions as osmoregulators in NaCl-stressed seedlings from aged and primed seeds. The combinations of two seed vigor levels (aged or not), two seed types (primed or not) and two salinity levels (exposed to NaCl at 100 mM or not) were evaluated. In low physiological quality seeds (aged seeds), priming provided an attenuation of salinitys negative effects (0 or NaCl at 100 mM) on seedling growth. The accumulation of Na+ and Cl- ions in NaCl-stressed sorghum seedling shoot from primed seeds indicate a plant osmotic adjustment induced by seed priming, which was efficient in reducing the osmotic stress caused by salinity. Proline was the main organic solute that contributed to osmoregulation in NaCl-stressed sorghum seedling shoot and its levels increased due to seed priming. Changes in inorganic and organic solute contents, in both shoot and roots, could have been induced by seed priming and as a function of salt stress tolerance, although the changes in these organs were poorly related to each other.

Physiological quality of sesame seeds produced from plants subjected to water stress

Germination and seed vigor may be influenced by several factors, such as water stress during production, which affect crops differently according to the phenological stage of the plant. The aim of this study therefore was to evaluate the physiological quality of sesame seeds from plants subjected to water stress at different phenological stages. To this end, sesame plants were subjected to water stress at the following stages: I - germination to the start of vegetative growth (T1); II - vegetative growth to flowering (T2); III - flowering to pod formation (T3); IV - fruit maturation (T4); also for stress at all stages (T5) and full irrigation (T6). By weighing and daily irrigation of the containers, levels were kept at 50% of pot capacity (CV) for treatments with water deficit, and at 100% CV for treatments with no deficit. At 90 days after planting, the plants were harvested. The seeds were evaluated by germination test, first germination count, germination speed index, mean germination time, accelerated aging, electrical conductivity, seedling emergence, emergence speed index, mean time of emergence, seedling length and seedling dry weight. Sesame seeds from plants grown under water deficit display lower physiological quality. Between germination and the start of vegetative growth, and between flowering and fruit formation, the sesame is more sensitive to water stress, so that water limitation during these periods results in the production of seeds of low physiological quality.

Avaliação citoquímica durante a germinação de sementes de sorgo envelhecidas artificialmente e osmocondicionadas, sob salinidade

The aim of this study was to evaluate the rate of water absorption and cytochemical changes in primed and aged seeds of sorghum during germination under absence or presence of 100 mM NaCl. The initial batch of seeds of sorghum cv. IPA-1011, was divided into two batches of different levels of vigor, by the accelerated aging of half seeds, with half of each batch also referred to the priming of polyethylene glycol 6000 at -0.86 MPa for 48 hours. Four replicates of 50 seeds from each batch were placed on two sheets of filter paper, blotting paper saturated with distilled water and placed inside gerboxes (11 x 11 x 3.5 cm) transparent lids, which were kept in a germination chamber under continuous darkness and 25 oC for 72 hours. The cytochemical analysis characterization was measured in the soaking times of 0; 24; 48 and 72 hours. The sorghum seeds cells showed irregular shapes, ranging from elliptical to rounded, and the staining with the toluidine blue also revealed the presence of nuclei, especially in primed seeds, indicating that some cells showed high cellular activity. The presence of protein was detected mainly in protein bodies on cytoplasm of cotyledon cells, while the starch was identified in the form of granules at endosperm. The accelerated aging treatments and seed priming, associated to salt stress resulted in little morphological and cytochemical visible changes during the experimental period analyzed.

Salinity Effects on Germination and Establishment of Sorghum Seedlings From Artificially Aged and Primed Seeds

The objective of this experiment was to assess the effect of salt stress on water uptake, germination and initial growth of seedlings from artificially aged and osmoconditioned sorghum (Sorghum bicolor [L.] Moench) seeds. A randomized block design with four replications (a 2 × 2 × 4 factorial design) was used. Two lots of seeds (aged or nonaged); two types of seeds (osmoconditioned or not osmoconditioned), and four levels of salt stress (0, 100, 200, or 300 mM of NaCl) were the factorial treatments. The evaluated parameters were water-uptake rate by the seeds, first count, standard test and speed index of germination, shoot and root lengths, and dry mass. Salt stress had a negative effect on grain sorghum seed; reduced water uptake, seed germination, and initial seedling growth were observed. Priming mitigated the harmful effects of salinity on germination and initial seedling growth from nonaged seeds, but it is not recommended for germination of low vigor seeds under high salinity.

Agronomic performance of onion hybrids in Baraúna, in the semi-arid region of Brazil

No estado do Rio Grande do Norte o plantio de cebola de forma mais expressiva e relativamente recente, sendo que produtores entao buscando alternativas como formas de diminuir os prejuizos. Em funcao disso, objetivou-se avaliar o desempenho agronomico de hibridos de cebola na regiao semiarida no municipio de Barauna - RN. O delineamento experimental foi o de blocos casualizados com seis repeticoes. Os tratamentos consistiram de oito hibridos (Cronus F1, Predileta F1, Serena F1, Fortaleza F1, Mata Hari, Luana, Lambada, Don Victor) e uma cultivar testemunha (IPA 11). Foi avaliada a altura media de plantas, o numero medio de folhas, o diâmetro do pseudocaule, a produtividade, a massa media dos bulbos, o indice de sobrevivencia, a cerosidade foliar, o ciclo das cultivares e a classificacao comercial de bulbos. As cultivares Serena F1 e Mata Hari sao recomendadas para a regiao semiarida nordestina em funcao da alta produtividade, ciclo precoce e melhor classificacao dos bulbos. O emprego dessas cultivares podera, em curto prazo, contribuir para mudar o panorama da cultura da cebola no Estado do Rio Grande do Norte.

Physiological and Biochemical Responses of Semiarid Plants Subjected to Water Stress

Plants are often subjected to periods of soil and atmospheric water deficits during their life cycle. Moreover, the faster-than-predicted change in global climate (Intergovernmental Panel on Climate Change, 2007) and the different available scenarios for climate change suggest an increase in aridity for the semiarid regions of the globe. Together with overpopulation, this will lead to an overexploitation of water resources for agriculture purposes and increased constraints on plant growth and survival and, therefore, on realizing crop yield potential (Chaves et al., 2003; Passioura, 2007). Water is one of the fundamental resources for the vital processes of vegetation. Plants need to maintain adequate levels of water in their tissues to assure growth and survival and to perform physiological processes, such as photosynthesis and nutrient uptake (Kramer & Boyer, 1995; Larcher, 1995; Nobel, 1999). In conditions of water deficit, plant cell turgor is reduced, and a series of harmful effects on plant physiology—e.g., reduction of cell growth, cell wall synthesis, protein synthesis, respiration, and sugar accumulation—occur, generating a state of increasing suffering in plants, usually named ‘water stress’ (Smith & Griffith, 1993; Lauenroth et al., 1994). Drought is the most important limiting factor for crop production; it is becoming an increasingly severe problem in many regions of the world. In addition to the complexity of drought itself (Passioura, 2007), plant responses to drought are complex, and different mechanisms are adopted by plants when they encounter drought (Jones, 2004). These mechanisms can include: (i) drought escape by rapid development, which allows plants to finish their cycle before severe water stress; (ii) drought avoidance by, for instance, increasing water uptake and reducing transpiration rate by the reduction of stomatal conductance and leaf area; (iii) drought tolerance by maintaining tissue turgor during water stress via osmotic adjustment, which allows plants to maintain growth under water stress; and (iv) resisting severe stress through survival mechanisms (Izanloo et al., 2008). However, this last mechanism is typically not relevant to agriculture (Tardieu, 2005). The maintenance of high plant water status and plant functions at low plant water potential and the recovery of plant function after water stress are the major physiological processes that contribute to the maintenance of high yield under cyclic drought periods (Blum, 1996).