Survival Percentage Of Seedlings Research Articles

Signal crosstalk between nitric oxide and hydrogen sulfide may be involved in hydrogen peroxide-induced thermotolerance in maize seedlings

Hydrogen peroxide (H2O2) and nitric oxide (NO) function as signal molecules in plant cells. Recently, hydrogen sulfide (H2S) has been found to have similar functions, but their interactions in the acquisition of thermotolerance in plants remain elusive. In current work, pretreatment with H2O2 rapidly induced endogenous H2O2 accumulation, which in turn improved survival percentage of maize seedlings (Zea mays L.) under heat stress, but these effects were eliminated by H2O2 scavenger dimethylthiourea indicating that H2O2-induced thermotolerance was involved in the accumulation of endogenous H2O2. H2O2 pretreatment also increased endogenous NO content, but this increase was abolished by NO scavenger cPTIO. Exogenously applied H2O2 also stimulated increase in the activity of L-cystine desulfhydrase, a key enzyme in H2S biosyn-thesis, followed by inducing endogenous H2S accumulation, while this accumulation was diminished by cPTIO. In addition, H2O2-induced thermotolerance was enhanced by NO donor sodium nitroprusside and H2S donors NaHS as well as GYY4137, respectively, and weakened by cPTIO, DL-propargylglycine (inhibitor of H2S biosynthesis) and hypotaurine (H2S scavenger). All of the above-mentioned results showed that H2O2 treatment could improve thermotolerance in maize seedlings, and the acquisition of thermotolerance induced by H2O2 may be involved in downstream signal crosstalk between NO and H2S.

Association mapping of seed germination and seedling growth at three conditions in indica rice (Oryza sativa L.)

Seed germination and seedling establishment are critical phases in rice. In this study, 276 indica accessions were used to investigate the genetic control of seed germination and seedling growth under normal, drought and salt conditions by using the trait of germination percentage, germination index and seedling survival percentage. The significant natural variation of seed germination and seedling growth was observed among accessions at three conditions. Correlation analysis showed that the significant and positive relationship between drought and salt stress conditions was observed in seed germination while not in seedling growth. A total of 12, 14 and 9 simple sequence repeat (SSR) markers associated with three traits were identified under normal, drought and salt conditions respectively. Seven and two SSR loci were simultaneously identified at two and three conditions, respectively, five SSR loci each were specific for drought and salt stress condition. By comparing chromosomal positions of the markers here with previously studies, six SSR loci might represent novel. Several accessions with elite performance of seed germination and seedling growth under stress conditions were firstly identified, such as Gulfrose, Kaijiangliushizao, Yangxidao and Xincunheigu. Six cross combinations each for improving seed germination and seedling growth under stress conditions were predicted. The identified elite accessions and alleles might be applicable to improve rice seed germination and seedling growth by the marker-assisted selection approach.

Effects of Cultivation System and Fertilization on Seedling Production of <i> Ocimum basilicum</i> L. and <i>Mentha spicata</i> L.

The demand for aromatic plants as ornamentals and sources of essential oils has increased recently. A float system is a promising alternative method of seedling production. Two cropping systems, float and conventional (seed bed), and two nutrient solution formulations, one organic and one inorganic, were evaluated for Ocimum basilicum (basil) and Mentha spicata (spearmint) seedling production. Basil seedlings grown in float system had better or comparable growth of shoots and leaves with those grown in seedbeds, irrespective of the fertilization, whereas spearmint organic fertilization reduced the growth of the aboveground parts of the seedlings, regardless of the cropping system. By contrast, fertilization treatments on both species’ seedling grown in float system showed better root length and higher root biomass accumulation. The survival percentage of seedlings after transplanting, as well as the subsequent growth of plants, were not seriously affected by the cropping system of the fertilization method during transplant production. Overall, we conclude that a float system can be used for the production of Ocimum basilicum and Mentha spicata seedlings under organic or inorganic fertilization.

Hydrogen sulfide acts as a downstream signal molecule in salicylic acid-induced heat tolerance in maize (Zea mays L.) seedlings

Salicylic acid (SA), 2-hydroxy benzoic acid, is a small phenolic compound with multifunction that is involved in plant growth, development, and the acquisition of stress tolerance. In recent years, hydrogen sulfide (H2S) has been found to have similar functions, but cross talk between SA and H2S in the acquisition of heat tolerance is not clear. In this study, pretreatment of maize seedlings with SA improved the survival percentage of seedlings under heat stress, indicating that SA pretreatment could improve the heat tolerance of maize seedlings. In addition, treatment with SA enhanced the activity of L-cysteine desulfhydrase (L-DES), a key enzyme in H2S biosynthesis, which in turn induced accumulation of endogenous H2S. Interestingly, SA-induced heat tolerance was enhanced by addition of NaHS, a H2S donor, but weakened by specific inhibitors of H2S biosynthesis DL-propargylglycine (PAG) and its scavenger hydroxylamine (HT). Furthermore, pretreatment with paclobutrazol (PAC) and 2-aminoindan-2-phosphonic acid (AIP), inhibitors of SA biosynthesis, had no significant effect on NaHS-induced heat tolerance of maize seedlings. Similarly, significant change in the activities of phenylalanine ammonia lyase (PAL) and benzoic-acid-2-hydroxylase (BA2H), the key enzymes in SA biosynthesis, and the content of endogenous SA, was not observed in maize seedlings by NaHS treatment. All of the above-mentioned results suggest that SA pretreatment could improve the heat tolerance of maize seedlings, and H2S might be a novel downstream signal molecule in SA-induced heat tolerance.

Seed Germination and Seedling Survival Percentage of Shorea robusta Gaertn.f. in Buffer Areas of Similipal Biosphere Reserve, Odisha, India

Seed germination and seedling survival percentage of Shorea robusta was studied in Similipal Biosphere Reserve (SBR) from 2010 to 2011. During the investigation period it was found that larger seeds (12 to 14 mm diameter) exhibited higher germination percentage (70 ± 6.5%) and all the seedlings survived. On the other hand, smaller seeds showed a very low percentage of germination (25 ± 4.24%) and none of the seedlings survived. It was also noticed from the study that the growth phase of the parent tree has a prominent effect on the germination potential of seeds. Juvenile trees with Girth at Breast Height (GBH) 75 to 80 cm as well as over mature (GBH: 91 to105 cm) or senile trees (GBH: 106 to 150 cm) produce seeds with a lesser germination capacity. However, young trees (GBH: 81 to 90 cm) produce seeds with a higher germination potential. Not only these aspects but also the orientation of seeds showed a peculiar phenomenon during natural germination. Maximum percentage (85 ± 12.75%) of seed germination was marked in case of seeds fallen on the forest floor in inverted position in comparison to other seed orientation types i.e. upright and horizontal. The uprightly falling seeds on the forest floor exhibited the minimum percentage (32 ± 6.84%) of germination, while horizontally falling seeds showed an intermediate range of germination percentage. Percentage survival of seedlings also followed the same pattern.

Hydrogen sulfide donor sodium hydrosulfide-induced accumulation of betaine is involved in the acquisition of heat tolerance in maize seedlings

Hydrogen sulfide (H2S) which is involved in plant growth, development, and the acquisition of stress tolerance including heat tolerance, is considered as the third signal molecule after nitric oxide and reactive oxygen species, while betaine is an important osmolyte with multiple physiological functions, but interaction between H2S and betaine in the acquisition of heat tolerance in plants is not clear. In this study, pretreatment with H2S donor sodium hydrosulfide (NaHS), as comparison to the control seedlings without NaHS treatment, significantly improved the activity of betaine aldehyde dehydrogenase (BADH), a key enzyme in the biosynthesis of betaine, which in turn induced the accumulation of endogenous betaine, eventually enhanced the survival percentage of maize seedlings under heat stress. In contrast, these effects induced by NaHS were eliminated by application of H2S scavenger hypotaurine and inhibitor of BADH disulfiram, respectively, indicating that H2S-improved heat tolerance of maize seedlings may be closely associated with the accumulation of endogenous betaine by activating the activity of BADH. In addition, exogenous betaine treatment enhanced the content of endogenous betaine, followed by improved the survival percentage of maize seedlings compared with the control without betaine treatment. All of the above-mentioned results showed that NaHS pretreatment could induce the accumulation of endogenous betaine by increasing BADH activity, and this accumulation may be involved in the acquisition of heat tolerance of maize seedlings, bridging a gap between H2S and betaine in the acquisition of heat tolerance in plants.

Effect of pretreatment with hydrogen sulfide donor sodium hydrosulfide on heat tolerance in relation to antioxidant system in maize (Zea mays) seedlings

Hydrogen sulfide (H2S) is a signal molecule that is involved in plant growth, development and the acquisition of stress tolerance including heat tolerance, but the mechanism of H2S-induced heat tolerance is not completely clear. In present study, the effect of sodium hydrosulfide (NaHS), a H2S donor, treatment on heat tolerance of maize seedlings in relation to antioxidant system was investigated. The results showed that NaHS treatment improved survival percentage of maize seedlings under heat stress in a concentration-dependent manner, indicating that H2 St reatment could improve heat tolerance of maize seedlings. To further study mechanism of NaHS-induced heat tolerance, catalase (CAT), guaiacol peroxidase (GPX), superoxide dismutase (SOD), glutathione reductase (GR) and ascorbate peroxidase (APX) activities, and glutathione (GSH) and ascorbic acid (AsA) contents in maize seedlings were determined. The results showed that NaHS treatment increased the activities of CAT, GPX, SOD and GR, and GSH and AsA contents as well as the ratio of reduced antioxidants to total antioxidants (AsA/(AsA+DHA) and GSH/(GSH +GSSG)) in maize seedlings under normal culture conditions compared with the control. Under heat stress, antioxidant enzymes activities, antioxidants contents and the ratio of the reduced antioxidants to total antioxidants in control and treated seedlings all decreased, but NaHS-treated seedlings maintained higher antioxidant enzymes activities and antioxidants levels as well as the ratio of reduced antioxidants to total antioxidants. All of above-mentioned results suggested that NaHS treatment could improve heat tolerance of maize seedlings, and the acquisition of this heat tolerance may be relation to enhanced antioxidant system activity.

Involvement of trehalose in hydrogen sulfide donor sodium hydrosulfide-induced the acquisition of heat tolerance in maize (Zea mays L.) seedlings.

BackgroundTrehalose, a non-reducing disaccharide, which involves in the acquisition of various stress tolerance, while hydrogen sulfide (H2S) is considered as a cell signal molecule, but H2S-induced heat tolerance and involvement of trehalose in plants is still unclear.ResultsIn present study, pretreatment with hydrogen sulfide donor sodium hydrosulfide (NaHS) markedly increased the accumulation of endogenous H2S in maize seedlings under normal culture conditions, which in turn improved survival percentage of maize seedlings and mitigated increase in electrolyte leakage and malonaldehyde (MDA) accumulation under heat stress. In addition, treatment with NaHS activated increase in the activity of trehalose-6-phosphate phosphatase (TPP) under normal culture conditions, followed by induced the accumulation of endogenous trehalose, but this accumulation was eliminated by addition of sodium citrate, an inhibitor of TPP. During the process of heat stress, maize seedlings treated with NaHS maintained higher TPP activity and trehalose content than those of control. On the other hand, exogenous application of trehalose also increased the content of endogenous trehalose in maize seedlings under normal culture conditions, alleviated increase in electrolyte leakage and MDA accumulation under heat stress, which in turn improved survival percentage of maize seedlings, and the heat tolerance induced by trehalose was enhanced by exogenous supplement of NaHS, but exogenous trehalose treatment had not significant effect on the accumulation of endogenous hydrogen sulfide in maize seedlings.ConclusionThese data suggest that sodium hydrosulfide pretreatment could improve heat tolerance of maize seedlings and this improvement may be involved in trehalose accumulation by activating TPP activity.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-55-20) contains supplementary material, which is available to authorized users.

Crescimento de Mudas de Eucalyptus grandis e Eremanthus erythropappus sob Diferentes Formulações de Substrato

O objetivo deste trabalho foi avaliar a sobrevivencia e o crescimento de mudas de Eucalyptus grandis e Eremanthus erythropappus, alem de analisar o custo do substrato produzido, em funcao de diferentes formulacoes utilizadas. Dessa forma, para cada especie, foi utilizado um experimento instalado em delineamento inteiramente casualizado (DIC), com as dez formulacoes de substrato contendo esterco de curral curtido, casca de arroz carbonizada, fibra de coco - estes variando nas proporcoes de 0, 30, 60 e 90% - e vermiculita media (10%). Ao final do processo de producao, foram quantificados: o percentual de sobrevivencia, a altura da parte aerea e o diâmetro do coleto das mudas. Alem disso, foi calculado o custo para produzir um metro cubico de cada um dos dez substratos analisados. Verificou-se que os substratos influenciam significativamente o crescimento de ambas as especies, sendo que o esterco influenciou de forma negativa no crescimento das mudas de candeia, enquanto, para o eucalipto, influenciou positivamente. O aumento de proporcoes de esterco diminuiu o custo por metro cubico de substrato.

Successional Distance between the Source and Recipient Influence Seed Germination and Seedling Survival during Surface Soil Replacement in SW China

Adding propagules (source) to a degraded site (recipient) is a common way of manipulating secondary succession to restore diversity and services formerly provided by forests. However, heretofore no study has considered the effect of “successional distance” between source and recipient site. Four sites in the Shilin karst area of SW China were treated as different states along a secondary successional sere: grass, shrub, young secondary forest, and primary forest. Ten 1 m ×1m soil quadrats in the grass, shrub and young forest sites were replaced with 10 cm deep soil sources from corresponding later successional stage(s) in January 2009. Woody plant seed germination was monitored in the first year and seedling survival was monitored until the end of the second year. At the end of 2010, 2097 seeds of woody plants belonging to 45 taxa had germinated, and 3.9% of the seedlings and 7.8% of the species survived. Germination of most species was sensitive to ambient light (red, far-red, R:FR ratios, photosynthetically active radiation). Soil source and recipient site had a significant effect on the total number of seeds and number of species that germinated, and on the percentage of seedlings that survived through the end of the second year. Closer successional stages between recipient site and soil source had higher seed germination and seedling-survival percentages. However, a transition threshold exists in the young forest state, where seeds can germinate but not survive the second year. Our results, although based on an unreplicated chronosequence, suggest that successional distance between soil sources and recipient sites affect forest recruitment and restoration in degraded karst of SW China.

Identification of QTLs for cold tolerance at seedling stage in rice (Oryza sativa L.) using two distinct methods of cold treatment

Cold water irrigation and growth in low temperature phytotron are two commonly used methods to evaluate cold tolerance of rice at the seedling stage and the cold sensitive seedlings exhibit different injury symptoms, respectively. However, so far no one has systematically dissected the differences of cold tolerance at seedling stage in rice under the two cold environments. We used a recombinant inbred line (RIL) population derived from a cross of a cold-tolerant japonica cultivar, Lijiangxintuanheigu and a cold sensitive indica cultivar, Sanhuangzhan-2 for this study. The cold sensitive seedlings exhibited leaf yellowing after cold water irrigation and leaf rolling during growth in the low temperature phytotron. Leaf yellowing and leaf rolling in RILs was significantly correlated, but the correlation coefficient was low. A total of four quantitative trait locus (QTLs) on chromosomes 1, 6, 9 and 12 were detected using leaf yellowing and percent seedling survival as indicators of cold tolerance after cold water irrigation, while five QTLs on chromosomes 7, 8, 9, 11 and 12 were detected using leaf rolling and percent seedling survival as indicators of cold tolerance during growth in the low temperature phytotron. The two QTLs, qCTS-9 and qCTS-12 were detected using different evaluation indicators under the two cold environments. Our results suggest that rice cold tolerance mechanisms at the seedling stage differ between the two environments, but the detection of common QTL implies the existence of overlap in the metabolic pathways for cold tolerance. The two common QTLs have potential value in rice breeding.

Pulp fruit added to culture medium for in vitro orchid development

As an additive in in vitro culture media, fruits have a great potential for facilitating economical orchid production because of lower technology requirements and the ease of obtaining raw materials to formulate culture media. We studied the in vitro growth of Cattleya bicolor Lindl. grown in a simplified culture medium supplemented with different kinds of fruit pulp. The experimental design was completely randomised, with eight seedlings per replication and ten replications per treatment, for a total of 80 seedlings per treatment. The culture medium was made using 150 g L -1 of pulp (without peel or seed) from the following fruits: ripe Santa Cruz tomatoes (Solanum lycopersicum L.), dwarf bananas (Musa cavendishii L.) of intermediate ripeness, light green chayote (Sechium edule (Jacq.) Sw), ripe papaya (Carica papaya L.) or green coconut (Cocos nucifera L.).The treatment control was MS 50 %. The treatments and the control were kept in a growth chamber for seven months before evaluating seedling survival percentage, shoot height, number of leaves, rooting percentage, root number, root length and dry masses of shoot and roots. The highest percentages of seedling survival were obtained using MS 50 %, banana and coconut medium. The seedling survival and rooting percentages illustrate that it is possible to emphasise the culture medium MS 50% and the culture medium supplemented with coconut on the most traditional culture medium with banana or tomato pulp. For the in vitro development of Cattleya bicolor Lindl., a simplified culture medium supplemented with coconut pulp is the most suitable for use as an alternative to MS 50%. A simplified culture medium supplemented with papaya pulp is not recommended for the in vitro development of Cattleya bicolor Lindl.

Hydrogen sulphide may be a novel downstream signal molecule in nitric oxide‐induced heat tolerance of maize (Zea mays L.) seedlings

Nitric oxide (NO) is a second messenger with multifunction that is involved in plant growth, development and the acquisition of stress tolerance. In recent years, hydrogen sulphide (H(2)S) has been found to have similar functions, but crosstalk between NO and H(2)S in the acquisition of heat tolerance is not clear. In this study, pretreatment with the NO donor sodium nitroprusside (SNP) improved the survival percentage of maize seedlings and alleviated an increase in electrolyte leakage and a decrease in tissue vitality as well as accumulation of malondialdehyde, indicating that pretreatment with SNP improved the heat tolerance of maize seedlings. In addition, pretreatment with SNP enhanced the activity of L-cystine desulfhydrase, which, in turn, induced accumulation of endogenous H(2)S, while application of H(2)S donors, NaHS and GYY4137, increased endogenous H(2)S content, followed by mitigating increase in electrolyte leakage and enhanced survival percentage of seedlings under heat stress. Interestingly, SNP-induced heat tolerance was enhanced by application of NaHS and GYY4137, but was eliminated by inhibitors of H(2)S synthesis DL-propargylglycine, aminooxyacetic acid, potassium pyruvate and hydroxylamine, and the H(2)S scavenger hypotaurine. All of the above-mentioned results suggest that SNP pretreatment could improve heat tolerance, and H(2)S may be a downstream signal molecule in NO-induced heat tolerance of maize seedlings.

English

Management and transmission of four seed-borne pathogenic fungi namely,Colletotrichum trifolii,  Rhizoctonia solani, Fusarium equiseti and F. incarnatum were investigated on alfalfa plants. The pathogenicity test on alfalf plant showed that R. solaniand C. trifolii caused  high percentages of rotted seeds and seedlings mortality (26.45, 26.1% and 31.6,  21.1% , respectively). However, no significant differences were observed between the treatments with F. equiseti and F. incarnatum when compared with the control treatment. Transmission of the pathogenic fungi from seed to mature plant of alfalfa was investigated in this study. Results indicate that the recovery percentages of the tested pathogens gradually decreased from root apex up to the first internodes below the shoot tip, but did not reach to the shoot apex. In order to control these fungi, different concentrations of sodium metabisulphite (SM), sodium salicylate (SS) and hydroquinone (HQ) were tested in vitro. Treatment with SM at 10 mM completely inhibited the growth of all isolated fungi. Under greenhouse conditions, soaking alfalfa seeds in a water solution of hydroquinone at 12mM showed to be the most effective treatment in reducing seed rot and seedling mortality percentages and increasing seedling survival percentages. Application of the tested treatments presented significant increases in growth parameters, photosynthetic pigments (chlorophyll a and b and carotenoids) in leaves and total phenol in alfalfa plants. This study therefore recomended the use of HQ and SM as potential and promising antifungal agents in  the protection of alfalfa plants against the tested seed-borne fungi.   Key words: Pathogenicity, Colletotrichum trifolii, Rhizoctonia solani, Fusarium equiseti, F. incarnatum, transmission, hydroquinone, sodium metabisulphite and sodium salicylate.

Hydrogen sulfide donor sodium hydrosulfide-improved heat tolerance in maize and involvement of proline

Hydrogen sulfide (H2S) has long been considered as a phytotoxin, but nowadays as a cell signal molecule involved in growth, development, and the acquisition of stress tolerance in higher plants. In the present study, hydrogen sulfide donor, sodium hydrosulfide (NaHS), pretreatment markedly improved germination percentage of seeds and survival percentage of seedlings of maize under heat stress, and alleviated an increase in electrolyte leakage of roots, a decrease in tissue vitality and an accumulation of malondialdehyde (MDA) in coleoptiles of maize seedlings. In addition, pretreatment of NaHS could improve the activity of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and lower proline dehydrogenase (ProDH) activity, which in turn induced accumulation of endogenous proline in maize seedlings. Also, application of proline could enhance endogenous proline content, followed by mitigated accumulation of MDA and increased survival percentage of maize seedlings under heat stress. These results suggest that sodium hydrosulfide pretreatment could improve heat tolerance of maize and the acquisition of this heat tolerance may be involved in proline.

Regeneration niche of three epiphytic species of Gesneriaceae from Chilean rainforests: implications for the evolution of growth habits in Coronanthereae

Ecological and evolutionary studies of the epiphytic growth habit in angiosperms are limited. In this article, we assess the relationship between growth habit and regeneration niche in Coronanthereae (Gesneriaceae) and discuss its implications for the evolution of epiphytism in this lineage. In the temperate rainforest of southern Chile, we quantified the vertical distribution and experimentally examined the regeneration niche of three endemic species of Coronanthereae. One species was a holoepiphyte, which was more frequent in the upper canopy, and two species were secondary hemiepiphytes, which decreased in abundance with tree height. Seed germination of the holoepiphyte was higher on tree bark substrates and under open canopy than on forest soil and in the shade. In contrast, seed germination of both secondary hemiepiphytes did not differ between substrates (bark vs. soil) or light conditions (light vs. shade). Seedling survival percentage of secondary hemiepiphytes was higher on forest soil and under a closed canopy, thus behaving as shade-tolerant species. In turn, the holoepiphyte behaved as a shadeintolerant species. The reconstruction of the ancestral growth habits and regeneration niches on the inferred phylogenetic tree of Coronanthereae revealed that the specialized regeneration niche of Sarmienta repens, characterized by requirements of shade intolerance and germination on tree bark, was coupled with the evolution of the holoepiphytic growth habit. We conclude that differentiation in the regeneration niche is a key process in the evolution of epiphytic growth habits in Coronanthereae. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170, 79‐92. ADDITIONAL KEYWORDS: Asteranthera ovata ‐ holoepiphyte ‐ light ‐ Mitraria coccinea ‐ Sarmienta repens ‐ secondary hemiepiphyte ‐ seed germination ‐ seedling survival ‐ substrate.

Associação entre características da parte aérea e do sistema radicular em mudas de guaranazeiro por correlações canônicas

Este trabalho teve como objetivo quantificar o grau de asociação entre variáveis de parte aérea e de raízes em mudas clonadas de guaranazeiro, utilizando-se correlações canônicas, a fim de aperfeiçoar o procedimento de seleção de mudas para garantir o aumento da porcentagem de sobrevivência das mudas após o plantio. Foram avaliados dois grupos de variáveis em mudas aptas ao plantio definitivo de 36 clones de guaranazeiro. O delineamento usado foi o aleatorizado em blocos com cinco repetições e 10 plantas por parcela, sob condições de viveiro. Os caracteres avaliados foram submetidos à análise de correlações canônicas. Utilizou-se a análise de correlações canônicas. O grupo de variáveis da parte aérea não se mostrou independente do grupo de variáveis do sistema radicular. Através de seleção baseada em variáveis da parte aérea pode-se melhorar o sistema radicular, principalmente através do maior comprimento do ramo (CRA). A seleção de clones de guaraná para maior peso de raiz pode ser efetuada de forma indireta, realizando-se mensurações do comprimento dos ramos, o que evita a necessidade de se destruir as mudas.

Genetic variability in seed and seedling traits of Jatropha curcas L.

Twenty two Jatropha curcas L. seed sources representing the states of Gujarat, Maharashtra, Madhya Pradesh, Uttarakhand, Haryana, Punjab and Rajasthan were evaluated to assess the genetic variability of seed and seedling traits during April to October, 2005 under statistically randomized block design with three replications to study the genetic variability of seed and seedling traits of Jatropha curcas L. The characters studied were 100 seed weight, seed length, seed width, germination percentage, germinative energy, seedling height, seedling collar diameter, number of leaves and seedling survival percentage. Genotypic variances were higher than the environmental variances for all the characters, thereby, indicating their importance for selection. The genotypic and phenotypic coefficient of variation was high for seedling survival percentage, seedling height and germination percentage. High heritability coupled with high genetic advance expressed as percent mean was observed for seedling survival, germinative energy, seedling height and germination percentage. The characters namely seedling collar diameter, 100 seed weight and seed width exhibited high heritability coupled with medium genetic advance expressed as percent mean.

Micropropagação de Dioscorea multiflora Grised

Dioscorea multiflora uma planta nativa do Sul do Brasil produz a diosgenina como metabólito secundário majoritário, uma substância potencialmente usada pela indústria farmacêutica para a produção de cortisona e substâncias com ação contraceptiva. Objetivou-se, neste trabalho otimizar o protocolo de micropropagação de D. multiflora, visando a produção de mudas em escala comercial. Segmentos nodais subcultivados em meio MS sólido foram transferidos para multiplicação em meio MS suplementado com BAP (0,01; 0,1; 0,5; 1,0 e 3,0 mg L-1)e meio MS suplementado com 0,1 mg L-1 ou 0,5 mg L-1 de BAP acrescido de diferentes concentrações de sacarose (2, 4, 6, 8 e 10%). Para o enraizamento, as brotações foram cultivadas em meio MS suplementado com AIB (0,1; 0,5; 1,0 e 3,0 mg L-1) e meio MS suplementado com ANA (0,1; 0,5; 1,0 e 3,0 mg L-1). Os experimentos in vitro foram instalados em delineamento experimental inteiramente casualizado e cada tratamento constituiu-se de 3 repetições e 10 cubetas/parcela. Plântulas com e sem raízes foram aclimatizadas em casa de vegetação. Melhores resultados de multiplicação e enraizamento foram obtidos em meio MS + 0,1 mg L-1 de BAP (80%) e em meio MS + 1,0 mg L-1 de AIB (42,6%), respectivamente. Não houve diferença quanto à porcentagem de sobrevivência das plântulas in vitro e ex vitro durante a aclimatização (75%). O protocolo de micropropagação para D. Multiflora é efetivo e pode ser usado para a produção em escala comercial.

Influence of stand density and soil treatment on the Spanish Black Pine (Pinus nigra Arn. ssp. Salzmannii) regeneration in Spain

Satisfactory results relating to the natural regeneration of the Spanish black pine (Pinus nigra Arn ssp. salzmannii) is generally difficult to achieve. The natural regeneration of this pine was studied comparing two types of soil treatment and various overstory densities in six experimental forests. These studies were conducted from 1999 to 2002 and seed rain and germination, as well as seedling survival were observed in a number of specific plots: Brushing, scalping and control plots. In addition various overstory densities were used (measured as base area (square m/ha). Soil and air temperature together with soil moisture were continuously recorded throughout this summer period. The results showed that seed germination was higher in plots using the scalping technique, as opposed to the brushed or controlled plots. The best seedling survival percentage was found in scalped plots together with a larger basal area. It was also found that seedling survival was lower during the first year than during the second one. The results have practical implications for management of Spanish black pine forests as well as valuable information which could improve the conditions for regeneration.