Abnormal Seedlings Research Articles

Physiological quality of coffee seeds produced under different levels of solar radiation and maturation stages

In Brazil, although the coffee plantations are predominantly grown under full sunlight, the use of agroforestry systems can lead to socioeconomic advantages, thus providing a favorable environment to the crop by promoting its sustainability as well as environmental preservation. However, there is a lack of information on physiological quality of the coffee seeds produced under different levels of solar radiation. Within this context, the objective of this study was to evaluate the influence of different levels of solar radiation and maturation stages on the physiological quality of coffee (Coffea arabica L.) seeds, cv. Acaiá Cerrado MG-1474. Three levels of solar radiation (plants grown under full sunlight; under plastic screens of 35% shading; and under plastic screens of 50% shading) and three maturation stages (cherry, greenish-yellow and green) were assessed. Physiological quality of seeds was assessed by using germination test, first count of germination, abnormal seedlings, dead seeds, and seedlings with open cotyledonary leaves. Electrophoretic analysis of isoenzymes catalase, esterase, superoxide dismutase and peroxidase was also performed. With the evolution of development the coffee seeds presents increases on physiological quality, and at its beginning the seeds show improvements on quality with the reduction of solar radiation.

Seed priming with antioxidants improves sunflower seed germination and seedling growth under unfavorable germination conditions

The results of studying the effects of sunflower seed priming with an aqueous solution of ascorbic acid (A), tocopherol (T), and glutathione (G) performed prior to accelerated ageing and a cold test are presented in this paper. Germination, the percentage of abnormal seedlings, and the lengths of both roots and shoots were monitored. The results showed that the cold test caused a drastic drop in germination, an adverse effect on the shoot length, an increase in the percentage of abnormal seedlings, and no effect on the root length. Germination of seeds primed with the solution of A, T, and G (A+T+G) on which the cold test was then performed did not differ from seed germination of the control. Moreover, seed priming with the A+T+G solution of antioxidant substances prior to the cold test annulled the adverse effect of the cold test on shoot length, as well as on the percentage of abnormal seedlings. Seed priming with the A+T+G solution of antioxidants did not affect root length. Accelerated ageing resulted in a statistically significant decrease in seed germination and root length, but neither shoot length nor the percentage of abnormal seedlings was affected by accelerated ageing. The obtained results show that seed priming with the solution of antioxidant substances performed prior to accelerated ageing had a positive effect on the length of both roots and shoots. Seed priming with the solution of antioxidant substances performed prior to accelerated ageing did not affect germination, but it did increase the percentage of abnormal seedlings. The effect of antioxidant solution priming on the vigor of sunflower seeds exposed to the cold test was significantly more pronounced than that on seeds exposed to accelerated ageing.

Procedimentos de colheita dos frutos na qualidade fisiológica de sementes de Sapindus saponaria Mart

Using the more appropriate method when harvesting the fruits is the best way to get maximum Sapindus saponaria seeds quality. Seed lots of Sapindus saponaria were harvested according to the following procedures: (1) green fruits attached to the plant, (2) yellow fruits attached to the plant, (3) brown fruits attached to the plant, (4) yellow fruits lying down on the ground, and (5) brown fruits lying down on the ground. In each case the seeds were extracted from the fruits and submitted to the following analyses: water content, germination at the first count (14 days), normal and abnormal seedlings at final count, dormant (hard) seeds at final count, and viable seeds at final count (37 days). Harvesting the fruits from the mother plant while still yellow was found to result in the best quality seeds although breaking seed dormancy was verified to be of necessity.

Procedimentos de colheita dos frutos na qualidade fisiológica de sementes de Sapindus saponaria Mart

Using the more appropriate method when harvesting the fruits is the best way to get maximum Sapindus saponaria seeds quality. Seed lots of Sapindus saponaria were harvested according to the following procedures: (1) green fruits attached to the plant, (2) yellow fruits attached to the plant, (3) brown fruits attached to the plant, (4) yellow fruits lying down on the ground, and (5) brown fruits lying down on the ground. In each case the seeds were extracted from the fruits and submitted to the following analyses: water content, germination at the first count (14 days), normal and abnormal seedlings at final count, dormant (hard) seeds at final count, and viable seeds at final count (37 days). Harvesting the fruits from the mother plant while still yellow was found to result in the best quality seeds although breaking seed dormancy was verified to be of necessity.

Tipos de substratos para germinação de sementes de palmeira- real-australiana (Archontophoenix alexandrae H. Wendl. & Drude)

Os objetivos deste trabalho foram avaliar o desempenho germinativo de sementes de palmeira-australiana em diferentes substratos e estabelecer a granulometria e intensidade de umedecimento adequado. A semeadura foi realizada com quatro repetições de 25 sementes em solo, areia, rolo de papel e em vermiculita de diferentes granulometrias: mícron (0,15-0,20 mm), superfina (0,21-0,30 mm), fina (0,30-0,50 mm) e média (1,19-0,50 mm), umedecidas com 0,5; 1,0; 1,5; e 2,0 vezes o seu peso em água. O teste de germinação foi conduzido a 20-30 °C, avaliando-se a primeira contagem do teste aos sete dias após a semeadura e, semanalmente, a germinação (plântulas normais) até os 35 dias, quando foram contabilizadas, também, as plântulas anormais e as sementes mortas. Calcularam-se o tempo médio e frequência relativa de germinação. A vermiculita mícron umedecida com uma vez o seu peso em água apresentou o melhor desempenho como substrato para o teste de germinação de sementes de palmeira-real-australiana, por possibilitar a máxima germinação das sementes (90%) e velocidade de germinação, demandando tempo médio de 15,3 dias nesse processo.

Down-regulation of UDP-glucuronic Acid Biosynthesis Leads to Swollen Plant Cell Walls and Severe Developmental Defects Associated with Changes in Pectic Polysaccharides

UDP-glucose dehydrogenase (UGD) plays a key role in the nucleotide sugar biosynthetic pathway, as its product UDP-glucuronic acid is the common precursor for arabinose, xylose, galacturonic acid, and apiose residues found in the cell wall. In this study we characterize an Arabidopsis thaliana double mutant ugd2,3 that lacks two of the four UGD isoforms. This mutant was obtained from a cross of ugd2 and ugd3 single mutants, which do not show phenotypical differences compared with the WT. In contrast, ugd2,3 has a strong dwarfed phenotype and often develops seedlings with severe root defects suggesting that the UGD2 and UGD3 isoforms act in concert. Differences in its cell wall composition in comparison to the WT were determined using biochemical methods indicating a significant reduction in arabinose, xylose, apiose, and galacturonic acid residues. Xyloglucan is less substituted with xylose, and pectins have a reduced amount of arabinan side chains. In particular, the amount of the apiose containing side chains A and B of rhamnogalacturonan II is strongly reduced, resulting in a swollen cell wall. The alternative pathway to UDP-glucuronic acid with the key enzyme myo-inositol oxygenase is not up-regulated in ugd2,3. The pathway also does not complement the ugd2,3 mutation, likely because the supply of myo-inositol is limited. Taken together, the presented data underline the importance of UDP GlcA for plant primary cell wall formation.

Chemical profile of Festuca arundinacea extract showing allelochemical activity

The allelopathic potential of fescue (Festuca arundinacea Shreb.) was investigated under field and laboratory conditions. In the field, incorporation of fescue aboveground biomass into the soil provided an effective weed control as it significantly reduced both the number and the dry weight of all weed species. The effect on weeds was species specific. The reduction of the most abundant species, Picris echioides, with respect to the number of individuals and their dry weight was 67 and 45%. Fescue aboveground biomass, harvested immediately before soil incorporation, was utilized in a bioassay-oriented fractionation, aimed at identifying the compounds in the toxic extracts of the plant. While phytotoxic activity was detected for the n-butanol fraction, no activity was found for the aqueous one. Germination of an indicator species, lettuce (Lactuca sativa L.), was reduced by 33% at the higher extract concentration of 20 mg/mL, owing to the increase of the number of abnormal seedlings. The LC/MS profile of the extract revealed the presence of two alkaloids, seven flavonol glycosides, and two flavonol aglyca. Quercetin 3-O-rutinoside, isorhamnetin 3-O-rutinoside, and kaempferol 3-O-rutinoside were reported in fescue for the first time.

Genome characterization of a Eucalyptusnatural mutant

Background Eucalyptus genetic improvement is time-consuming mainly because its long time to reach reproductive maturity along with its mixed mating system [6]. As a result, the production of pure lines as in maize is impracticable. The heterozygous status hides deleterious recessive genes that, when in homozygosity can reduce seedling survival due to physiological changes, resulting in considerable loss in seedling production [6]. Therefore, it would be important to identify the gene(s) associated with inbreeding depression. There are very few studies involving the characterization of deleterious recessive genes in Eucalyptus. We detected an anomaly in the offspring obtained from a controlled cross of Eucalyptus grandis. The anomaly appears in a ratio of one abnormal to three normal seedlings, suggestive of a Mendelian segregation. Based on the segregation ratio, we hypothesized that the character is controlled by a single gene, with a homozygous genotype for the recessive allele showing abnormal seedlings. The parents showed normal phenotype and they have no relationship, excluding the possibility of inbreeding depression due to identity by descent. The abnormal seedlings die in a few months and show different characters: high shoot branching, height reduction, leaf area reduction, and changes in leaf shape (Figure 1). In this scenario, we aimed to characterize the genomic and genetic causes of the observed anomaly. Methods The full-sib individuals generated at Suzano Papel and Celulose SA company were divided into normal and abnormal seedlings. The ratio between normal and abnormal seedlings was tested by chi-square analysis. DNA was extracted according to Ferreira and Grattapaglia [1]. The DNA concentration was quantified using a spectrophotometer (Thermo Scientific NanoDropTM 1000), and subjected to electrophoresis in 1% agarose gel and stained with ethidium bromide. DNA from ten normal individuals were randomly selected and mixed, creating the normal bulk, and the same was performed to create the abnormal bulk. The bulks were amplified with random primers (kits AD, AE, AF, AJ, and AK – Operon Technologies, Inc.). Amplicons were submitted to electrophoresis in 1% agarose gel stained with ethidium bromide. Polymorphic markers detected by RAPD were converted to SCAR (Sequence Characterized Amplified Regions) markers. DNA fragments from polymorphic marker were purified from agarose gel using the illustra GFX PCR DNA (GE Healthcare), cloned into vector pGEM-T Easy (Promega) and inserted into UltraMAX DH5a-FT competent Escherichia coli cells (Life Technologies). DNA was sequenced in an ABI3100 Genetic Analyzer (Applied Biosystems). SCAR primers were designed based upon the above mentioned sequencing and further used to amplify DNA fragments from bulks and six individuals: three anomalous, one individual from normal bulk; and two normal individuals of unrelated populations (BAC and Brasuz). Amplicons of the six individuals were purified, cloned into vector pGEM-T Easy (Promega) and inserted into DH5acompetent E. coli cells (Life Technologies). Six colonies from each individual were amplified with the SCAR primerss. Purified product of amplification was sequenced by ABI3100 Genetic Analyzer (Applied Biosystems). SCAR * Correspondence: mceciliapf@yahoo.com.br Departamento de Genetica, Instituto de Biociencias, Universidade Estadual Paulista (UNESP), Distrito de Rubiao Jr s/n CEP 18618-000, Botucatu (SP), Brazil Full list of author information is available at the end of the article Fuchs et al. BMC Proceedings 2011, 5(Suppl 7):P65 http://www.biomedcentral.com/1753-6561/5/S7/P65

Effects of Accelerated Aging on Soybean Seed Germination Indexes at Laboratory Conditions

Reduction of seedling growth is a consequence of seed deterioration. An experiment was conducted to evaluate the effects of duration of seed aging on soybean seed germination characteristics. Experiment conducted as completely randomized design with 4 replications. The seeds of ‘DPX’ line of soybean with 15-16% moisture were incubated for 3, 7, 10, 14, 17 day at 40 °C in sealed containers for ageing treatment and non aged seeds were considered as control. Results showed that rapid aging treatment has a significant effect on studied parameters. Germination percent (GP), means of daily germination (MDG), means time to germination (MTG), coefficient of velocity of germination (CVG) and germination index (GI) decrease significantly. Also, germination uniformity (GU) was affected by deterioration time. Abnormal seedling (ABS) percentage increased. Results shows that rapid aging experiment could be a useful test for determine soybean seed quality.

Relationship between germination and bell pepper seed structure assessed by the X-ray test

Alternative use of the X-ray test to evaluate seed quality has become increasingly diverse. This study was performed primarily to establish experimental procedures and verify the effectiveness of the X-ray test to detect damage or abnormalities in bell pepper (Capsicum annuum) seed structure associated with germination. Five seed lots each of hybrids Reinger and Sentinel were used. Two hundred seeds per lot were exposed to durations and intensities of X-radiation and visually classified into four categories according to the proportion between the area occupied by the embryo and endosperm in relation to the total cavity area in the internal seed structure, e.g. 0, < 50%, 50-75% and 100%. The last category was subdivided into two others based on the occurrence of morphological abnormalities. Seed samples obtained from different X-ray categories were then submitted to germination test at 25ºC for 14 days and subsequently compared with results of the X-ray analysis. Exposure to a 10 kV radiation for 260 s was the most suitable X-ray dose for visualizing seed structure. Seeds in which the area of the internal cavity occupied by the embryo and endosperm varied from 50-75% produced abnormal seedlings or did not germinate. Full seeds (100% of the internal cavity area occupied) with abnormal structure usually originated defective seedlings. As a consequence, the classification of bell pepper seeds according to the proportion occupied by the seed content (embryo + endosperm) allowed a reliable estimation of the degree of seed physical integrity based on X-ray analysis and its association with germination performance.

Lack of Evidence for Seed Transmission of 'Candidatus Liberibacter africanus' Associated with Greening (Huanglongbing) in Citrus in South Africa.

'Candidatus Liberibacter africanus' is associated with citrus greening (huanglongbing [HLB]) in South Africa. Various unpublished reports have suggested that the related bacterium 'Ca. L. asiaticus' associated with HLB in citrus might be seed transmissible based on real-time PCR results. Seed transmission poses a risk of long distance disease spread, especially with the dissemination of rootstock seed. Therefore, it was essential to determine whether 'Ca. L. africanus' is seed transmitted in citrus. Fruit from 26 'Ca. L. africanus'-infected branches of six citrus cultivars showing greening symptoms were collected and the seed was harvested. Cultivars included were Minneola tangelo (Citrus reticulata × C. paradisi); sweet oranges (C. sinensis) Premier midseason, Clanor midseason, and Olinda Valencia; Eureka lemon (C. limon) and Troyer citrange (Poncirus trifoliata × C. sinensis) rootstock variety. Branches bearing each fruit were collected and confirmed to contain 'Ca. L. africanus' by real-time PCR testing using Taqman probe HLBp and HLBaf and HLBr primers as described by Li et al. (3). The seed of each sample was sorted into five categories ranging from healthy looking to totally aborted based on their appearance before planting. Germination was done in seed trays under vector-free conditions at 24 to 28°C. Thereafter the seedlings were planted in small, plastic bags and monitored for greening-like symptoms or other abnormalities for up to 2 years. A slow-release, balanced fertilizer was applied and supplemented with micro-nutrient sprays for plant maintenance. Plants showing abnormal symptoms were potted into larger pots and closely monitored. These samples and a number of other seedlings showing growth abnormalities were tested for 'Ca. L. africanus' by real-time PCR as described above. In total, 1,570 seedlings were obtained. Some abnormal symptoms such as small chlorotic leaves, interveinal chlorosis, yellow veins, and stunting were seen in some seedlings. Most symptoms resembled deficiencies, and no blotchy mottle typical of 'Ca. L. africanus' infection was noted on any of the seedlings. Abnormal seedlings arose from normal and abortive seed. One hundred and eighteen of these seedlings (8 Minneola tangelo; 24 Premier midseason, 42 Clanor midseason, 33 Olinda Valencia, and 11 Troyer citrange seedlings) were individually tested using real-time PCR for 'Ca. L. africanus' detection. These seedlings had germinated from essentially healthy-looking seed (category 1) to seeds with severe abnormalities (category 5) and 33, 24, 23, 30, and 8 seedlings, respectively, were tested from each of the five seed categories. No samples tested positive with real-time PCR based on a positive/negative threshold Cq value of 35. Buds of some seedlings that yielded the lowest Cq values above 35 were grafted onto healthy 'Madam vinous' sweet orange (C. sinensis) seedlings and monitored for symptom development for 3 months. No symptoms developed and all these indicators also tested negative for 'Ca. L. africanus', indicating the absence of a transmissible agent. Just as other researchers (1,2) have recently indicated a lack of evidence for seed transmission of 'Ca. L. asiaticus', no seed transmission of 'Ca. L. africanus' could be demonstrated in this experiment either.

Caracterización molecular y germinación de semillas de maíces criollos azules con envejecimiento acelerado.

El objetivo del presente estudio fue determinar el efecto delenvejecimie nto acelerado en semillas de varie dades criollasde maíz azul. En los laboratorios de la Universidad NacionalAutónoma de México y del Instituto Politécnico Nacional,semillas de cuatro varie dades criollas de maíz azul (Cuijingo,Cocotitlán, Puebla y Oaxaca), se sometie ron a dos tip os deenvejecimie nto acelerado: calor húmedo (41°C, 72 horas y100% h. r.) y calor seco (60°C, 48 horas). Se evaluaron: protrusiónradicular de 0 a 72 horas de imbibición y, a los sie tedías de incubación a 25°C, plántulas normales, anormales ysemillas muertas. Se obtuvo la caracterización molecular delos tratamie ntos mediante la RA PD y se construyeron los dendogramasrespectivos. En plántulas normales provenie ntes desemillas sin envejecimie nto acelerado, las varie dades Oaxacay Puebla fueron significativamente superiores. El peso secoen las plántulas disminuyó con el deterioro, sie ndo exigua concalor seco. La presencia de plántulas anormales se incrementócon ambos tip os de deterioro en el orden: Oaxaca, Puebla,Cocotitlán y Cuijingo. La diferenciación de los perfiles debandeo entre semillas testigo y deterioradas ocurrió con la secuencia:Oaxaca (31,6%), Cocotitlán (25,8%), Puebla (19,6%)y Cuijingo (18,6%). Estos valores de similitud, a los cuales seramificaron los perfiles genómicos, se asociaron de manera inversacon el nivel de vigor de las semillas, y directamente conla presencia de anormalidades en las plántulas obtenidas.

Growth of white clover seedlings treated with aqueous extracts of leaf and root of tough lovegrass

This study was carried out to investigate the effect of extracts of leaf and roots of tough lovegrass (Eragrostis plana) on seedling growth of white clover (Trifolium repens), in two experiments. The first experiment was conducted as a pilot test, in which two concentrations (30 and 60%) of leaf aqueous extract were tested. In Experiment II, source (leaf/root) and concentration (5 and 10%) of the extracts were combined. Distilled water was used as control in both trials. Fifty seedlings at 7 days of age were placed in gerbox containers on filter paper moistened with extracts and incubated at 25°C for 14 days. In the first experiment, percentage of normal seedlings decreased by 82.5% and 100% at the concentrations of 30% and 60%, respectively, which indicated the need to increase the dilution of the extracts. In the subsequent experiment, the extracts from the two sources, at 10% of concentration, reduced by 78% the percentage of normal seedling and increased the percentage of abnormal seedlings, which reached 27%. At 5% concentration, the leaf extract was the most deleterious treatment, resulting in greater mortality (M=27.6%) and abnormality (A=19.5%) of seedlings, compared to the root extract (M=4.8%; A=9.5%) and the control (M=2.4%; A=0.25%). The morphological changes caused by the extracts were radicle necrosis, retention of cotyledons and absence of secondary roots. The results suggest that allelopathic compounds from leaves and roots of tough lovegrass differ in chemical nature and/or concentration.

Adequação da metodologia para o teste de germinação de sementes de pitaia vermelha

Hylocereus undatus (Haw.), popularmente conhecida como pitaia vermelha é uma cactácea para a qual se tem registrado um aumento de consumo nos últimos anos e, por ser ainda pouco explorada, vários aspectos referentes à sua propagação ainda são desconhecidos. Até o momento, não existem critérios para a execução de testes de germinação para sementes dessa espécie, publicados nas Regras para Análise de Sementes. Nesse sentido, objetivou-se com este trabalho adequar a metodologia quanto ao substrato, temperatura e tempo de contagem inicial e final para o teste de germinação. Foram testados quatro substratos (rolo de papel, areia, vermiculita e solo) e quatro temperaturas (20, 25, 30 e 20-30°C). O efeito dos substratos no desempenho germinativo das sementes foi avaliado pelo teste de germinação e de primeira contagem instalado com quatro subamostras de 50 sementes. Foram feitas contagens diárias do número de plântulas emergidas até atingirem a estabilidade e, no final do experimento, foram avaliados a porcentagem de germinação das sementes, considerando as plântulas normais, anormais e sementes mortas. Concluiu-se que o teste de germinação de sementes de pitaia vermelha deve ser realizado à temperatura constante de 25°C em rolo de papel, com contagens inicial e final aos cinco e dez dias após a semeadura, respectivamente.

Hidden viability risks in the use of farm-saved small-grain seed

SUMMARYAgriculture must provide sustainable food security and economic development to meet future challenges; new cultivars and the use of quality seed will be key components of this. The use of farm-saved seed may increase due to imbalances between income and expenditure associated with farming. The present study characterized the quality of commonly used, and thereby easily available, farm-saved seed in Finland. Farmers provided 657 seed lot samples of spring barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.) that they intended to use for sowing. Germination, seed weight, seedling elongation and within-seed-lot variability were analysed. Information was available on region, number of seed generations and cultivar. The specific aims were to identify how many generations of farm-saved seed are generally used by farmers, whether there is any safe generation threshold and the variability of quality of the seed lots. It was found that 0·80–0·84 of barley seed lots exceeded the 0·85 minimum germination requirement for certified seed, but only 0·60 of wheat. The risk of poor establishment was higher in wheat if the seed was not tested: 0·13 of wheat seed lots had germination of ⩽0·65 and 0·06 of ⩽0·50, while for barley the proportions with inadequate germination were 0·03–0·05. At most, &gt;0·30 abnormal seedlings were recorded for barley and &gt;0·50 for wheat. Variation in seed size and seedling length within seed lots was important, and increase in the latter was associated with reduced germination. In combination with up to 0·14 lethal fungus-infected seed, this emphasizes the need for seed upgrading measures. No safe threshold for farm-saved seed generations was determined.

Atividade alelopática de extrato de sementes de juazeiro

Alelopatia é a liberação de substâncias vegetais inibidoras ou estimulantes no ambiente, podendo estar presente nas sementes de algumas espécies. O objetivo neste trabalho foi avaliar o potencial alelopático do extrato de sementes de juazeiro (Ziziphus joazeiro Mart.) na germinação de sementes de alface (Lactuca sativa L). O experimento foi conduzido em delineamento inteiramente casualizado com quatro repetições e cinco tratamentos (0, 25, 50, 75 e 100% de concentração do extrato bruto). O extrato bruto foi obtido após a extração de 50 g de sementes e agitação em liquidificador com 500 mL de água. Os resultados mostraram efeito alelopático do extrato dependendo da concentração. As maiores concentrações do extrato de sementes de juazeiro afetaram a percentagem e velocidade de germinação e as menores proporcionaram plântulas anormais. Portanto, o extrato apresentou efeito alelopático desfavorável à germinação de sementes de alface.

Effect of acid stress on germination and early seedling growth of red clover

The aim of this investigation was to estimate the effect of four pH levels of germination media (4, 5, 6 and 7) on seed germination energy (GE), germination (G), percentage of dead or infected seeds (DIS), percentage of hard seed (HS), normal (NS) and abnormal seedlings (AS), root length (RL), shoot length (ShL), seedling length (SeL), fresh weight (FW) and dry weight (DW) of seedling, and seedling vigor index (SVI) in two red clover genotypes (cv. K-17 and cv. Kolubara). The experiment was conducted in the laboratory conditions of the Institute for Animal Husbandry in Belgrade in January 2011. The pH levels of germination media had significant effect on the NS (P&lt;0.01), AS (P&lt;0.01), RL (P&lt;0.05), ShL (P&lt;0.01), SeL (P&lt;0.01), FW (P&lt;0.01) and SVI (P&lt;0.05). The lowest GE, G, NS, ShL, SeL, FW and SVI were found at pH 4. Also, the highest DIS, HS and AS were found at pH 4. The genotype had significant effect on HS (P&lt;0.01), RL (P&lt;0.01), ShL (P&lt;0.01), SeL (P&lt;0.01), FW (P&lt;0.01) and SVI (P&lt;0.01). Genotype and pH levels of germination media did not affect on GE, G, DIS and DW significantly.

Atividade alelopática do extrato aquoso de sementes de jurema preta na germinação de alface

Jurema preta (Mimosa tenuiflora (Willd.) Poir.) is a tree that is common in the semi-arid Northeast Region of Brazil. Its canopy is host to a number of species and M. tenuiflora may have allelopathic effects. This study aims to determine the allelopathic potential of aqueous extract of seeds of M. tenuiflora on seed germination and seedling growth in lettuce. Two experiments were conducted: one with the extract obtained at room temperature (25 °C) and another with the extract obtained at 100 °C. The experimental design was completely randomized with five standard concentrations of the extract (0, 25, 50, 75 and 100%) with five replications of 20 seeds. We evaluated the germination percentage (G), germination speed index (IVG), percentage of normal (PN) and abnormal (PA) seedlings, shoot (CPA) and root (CR) length of lettuce seedlings. The pH and conductivity of all extracts were measured. There was a negative allelopathic effect on seed and seedling growth in lettuce, with inhibition of the growth of the root and hypocotyl. The extract obtained at 100 °C at a concentration of 100% drastically reduced the germination of lettuce. The extracts at 75 and 100% obtained at room temperature and at 100 °C caused any abnormality in lettuce seedlings. It is thus concluded that aqueous extracts of seeds of M. tenuiflora have a negative allelopathic effect on seed and seedling growth in lettuce. ARTIGO doi:10.4322/rca.2012.001 Silveira et al. / Rev. Ci. Agra., v.54, n.2, p.101-106, Mai/Ago 2011

Use of X-ray to evaluate damage caused by weevils in cowpea seeds

In Brazil, the cowpea [Vigna unguiculata (L.) Walp], is important in the Northeast Region, where it is typically grown on family farms. The importance of the damage caused to the seed quality of this species by stored pests has been described in various studies. Using X-ray, it is possible to see the internal seed structures and identify possible changes and damage. The objective of this study was to identify the damage caused by the weevil [Callosobruchus maculatus (Fabr.)] by analyzing X-ray and evaluate its relationship to the physiological quality of the cowpea seed. Three cultivars were used (IPA-206, BRS-Pajeu and BRS-Potengi) and two lines (L 281.005 and L ESP 10). The samples were exposed to X-ray and germination test to determine the cause-effect relationship between weevil damage and seed germination. X-ray images were evaluated to determine damage severity and location in the seed. Seed damage classified as severe, located in the embryonic axis or in the cotyledons, resulted in abnormal seedlings or dead seeds. The X-ray test, therefore, is efficient for evaluating weevil damage in cowpea seeds and the damage caused to be associated with any resulting adverse germination effects.

Germination and Seedling Growth of Desmanthus illinoensis and Desmodium canadense in Response to Mechanical Scarification

Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. &amp; Fernald] and showy ticktrefoil [Desmodium canadense (L.) DC.] are legumes native to North America used during meadow restoration efforts. However, insufficient or slow germination or reduced emergence may result attributable to seedcoat-mediated reductions in permeability to water. The objective of this research was to determine the effectiveness of a single-speed electric scarifier lined with 40-grit sandpaper for increasing germination and seedling growth of two native legumes. Seeds of Illinois bundleflower and showy ticktrefoil were mechanically scarified for 3, 6, or 12 s before they were subjected to germination and vigor testing. After scarification, final germination percentage (FGP), germination rate, and uniformity at multiple temperatures (15, 20, and/or 20 to 30 °C) were improved for Illinois bundleflower. However, FGP decreased for showy ticktrefoil, whereas germination rate and uniformity increased. For both species, there was a decline in FGP with longer scarification durations. Illinois bundleflower seed subjected to scarification and accelerated aging (AA) had higher FGP than non-scarified seed subjected to AA (59% and 6%, respectively), whereas both scarified and non-scarified seed of showy ticktrefoil subjected to AA had low FGP (11% and 18%, respectively). Mechanical scarification increased electrical conductivity (EC) of leachates for both species, but scarified showy ticktrefoil seed subjected to AA resulted in the highest EC compared with all other treatments, indicating a reduction of vigor. Evaluation of a seedling grow-out test 3 weeks after sowing confirmed that emergence was enhanced after 3 s of mechanical scarification of Illinois bundleflower seed but that scarification of showy ticktrefoil seed decreased emergence and increased the number of abnormal seedlings. Mechanical scarification resulted in peripheral damage and seed tissue obliteration of both species as indicated by viewing with a stereomicroscope. We conclude that scarifier limitations caused excessive physical damage of showy ticktrefoil. For Illinois bundleflower, however, mechanical scarification using an electric scarifier increased emergence from 18% (non-scarified seed) to 77% after 3 s of scarification and FGP from 32% (non-scarified seed) to 87% after 3 s of scarification. Compared with responses from non-scarified Illinois bundleflower seeds, scarification treatment also resulted in 24% faster germination and 37% more uniformity.