Effect of water stress on seed germination and seedling growth in Oryza sativa L.

The effect of water stress induced by application of polyethylene glycol 6000 during seed germination and seedling growth of Oryza sativa L. cv. IAC 165 was analysed. The seed germination was inhibited by the decrease in the water potential of the medium, the inhibition being greater under white light than under continuous darkness. When the seedling was submitted to water stress (-0.51 MPa) white light inhibited growth of root, coleoptile-and leaf, while under no stress conditions white light caused increase in growth of root and leaf and only inhibition of coleoptile growth. © 1990 Kluwer Academic Publishers.

On the germination and dormancy of dispersal units of Brachiaria decumbens staff

The effect of light and temperature on germination of Brachiaria decumbens as well as the action of some dormancy breaking chemicals were tested. Two seed batches stored different times were used. The results show that seeds failed to respond to alternating temperature regimes and different light qualities. Seeds were indifferent to white light at 25°C. KNO3, ethanol and H2SO4 failed to break seed dormancy, whereas KCN and H2O2 partially reduced dormancy of two month stored seeds. The results suggest a metabolic character of dormancy in new (freshly collected) seeds and confirm the occurence of two types of dormancy in B. decumbens seeds.

Inhibitory effects of jackbean (Canavalia ensiformis L.) leaf residues on germination and vigour of crops and weeds

The effects of jackbean leaf residues incorporated in the soil on germination and seedlings growth of cucumber, radish and some weeds was examined. Trials were carried out under greenhouse conditions to (a) determine the amount of incorporated residue that is inhibitory to two test plants, (b) to determine if decomposition time changes the inhibitory levels of jackbean residues on test plants and (c) to determine the amount of residue that is inhibitory to the weed species. Jackbean leaf residues incorporated in soil at concentration of 2% or higher and allowed to decompose for a period of 0 to 2 weeks before sowing, reduced the initial growth of cucumber and radish and at different concentrations, reduced germination and growth of three weed species. These results suggest the presence of allelopathic components in Jackbean leaves that could affect seed germination and seedling development.

Effect of soil moisture content and the irrigation frequency on the sugarcane germination

The aim of this work was to observe the interaction between soil moisture and irrigation time intervals on the germination of sugarcane cv. RB785148 sets in semi-controlled conditions. One-bud sets of the variety RB785148 were germinated in ceramic pots filled with soil under a transparent PVC cover using soil humidity levels of 22, 25 and 30%, that were restored at intervals of 7, 14 and 21 days. The experiment was carried out at three different periods of the year: May-June/94; Oct.-Nov./94; and Mar.-Apr./95. The results indicate that the germination decreased mainly in function of the decrease in soil humidity, whereas irrigation interval have no statistical effect on germination. An interaction between humidity level and irrigation interval was observed. A variation of the timecourse of the germination could be observed when the results of the experiments installed at different dates were compared.

Pollen viability in Syagrus romanzoffiana and S. coronata (Arecaceae)

Palms of the Syagrus genus have several natural hybrids in Brazil. They are widely cultivated around the world as ornamental palm. S. romanzqffiana is the parental of natural hybrids with other Syagrus species that are potentially useful as palm cultivated for heart of palm production. The objective of this work was to evaluate the pollen grains viability got from plants grown in the Experimental Nursery of the FCAVJ/UNESP, Jaboticabal, SP, Brazil. Pollen grains were sampled from inflorescence in three occasions: in the right day of anthesis, one day before and one day after anthesis. For each day, the inflorescence was subdivided in apical, medium and basal portions where pollen grains were collected. The results shown that: a) for S. coronata there was no statistical differences in pollen viability (pollen viability average = 92.89%); b) for S. romanzoffiana the average pollen viability was 87.27%, 87.47% e 86.85% before, during and after the anthesis, respectively. The basal portion pollen grains had lower viability (85.19% - p<0.01) than those from the medium (88.17%) and the apical (88.46%) portion of the inflorescence. These results shown that both species have no problems with pollen viability and can be used as parental of hybrids with other Syagrus species.

Effect of five substrates and three seed types on Calendula officinalis (Asteraceae) germination and seedling development

The investigation was carried out during May - June 1996 in Agronomical Sciences College - UNESP, Campus de Botucatu. The objective was to study the effect of seed types (carenate, alate and orbicular) and different substrates (vermiculite, sand, soil, commercial mixture and producer's mixture) on Calendula officinalis germination and seedling development. The design was in randomized blocks, with 4 replications. The germination index of the seeds was evaluated, as well as the development of aerial part and root system of the seedlings. Results showed that seed types have no relation with seedling development, therefore, germination was better on alate and orbicular seeds in C. officinalis. With reference to the substrates, the producer's mixture and the commercial mixture gave better germination and seedling development.

Influence of light, plant density and disinfection in spore germination of fern blechnum brasiliense desv. blechnaceae

The present assay had as objective evaluating spore germination of Blechnum brasiliense in relation to light, plant density and disinfection. The assay was carried out at Jaboticabal, Sào Paulo State, Brazil, from February, 22 to June, 30, 1996. The experimental design was randomized blocks on a factorial scheme (3x2x2), consisting of 12 treatments, three environments (shade-house, dark-house and germination camera), 2 densities (0.005 grs and 0.010 grs of spores/treatment) and presence or absence of disinfection. The leaf coverage area (130 days) and the number of days necessary to germinate were evaluated. The germination camera data were not analysed because they were insignificant; consequently, the remining data were analysed on a 2×2×2 scheme. The shade-house provided larger green covering area and a faster germination. The density of 0.0 lOg of spore/treatments presented the largest green covering area. The supply of partial light was necessary for good germination. The interaction between the environment and the density had significant effect on the green covering area.

Protein requirements in larvae and adults of Scaptotrigona postica (Hymenoptera: Apidia, Meliponinae): Midgut proteolytic activity and pollen digestion

The number and degree of digestion of pollen grains in the midgut and rectum, the midgut proteolytic activity and the time of pollen grain passage through the digestive tract in the stingless bee Scaptotrigona postica (Latreille) have been analyzed. The results show similar protein requirements among larvae, nurse bees and queens, as well as between forager bees and old males, but these requirements are higher in individuals from the former groups than in those from the latter. Although protein requirements have been demonstrated to vary according to a bee's activity in the colony, they are similar among bees from different castes or sexes. These changes in feeding behavior are related to the bee's function and to less competition for nourishment among individuals of the colony. It is also noted that pollen grains took between 6 and 28 h to pass through the digestive tract. Pollen grains are irregularly accumulated in the various regions of the midgut, which may reflect functional differentiation throughout the midgut. © 2001 Elsevier B.V.

Phytochrome and light influence on germination and vigor of ocimum gratissimum L. (Lamiaceae) seeds under high irradiance conditions

Ocimum gratissimum seed germination (% germination and vigor) has been found as phytochrome dependent, having a typical High Irradiant Response (HIR). Seven treatments were tested: daylight (DL), red (R), far-red (FR), blue (B), green (G), dark (DK), and reversible (RVB). No statistical difference among the DL, R, FR, B, and G were found. DK and RVB were statistically equal and presented the lowest results. The germination also occurred in the DK treatment but in non-useful rates, and it was nonreversible in the RVB treatment. It allows these seeds to be classified as positively photoblastic. The minimum energy need to initiate the germination was evaluated by a fluency-response curve. It plotted four different exposition times to R light (1 second, 60 seconds, 1 hour, and 13 hours) against percent germination. Useful germination occurred only after 1 hour, confirming the high energy needed to incite the process. The germination rate increased with the raise of the photoequilibrium (j). The high positive correlation index found confirms the phytochrome influence in this process. Facing all the results presented here, it is suggested to sow these seeds under direct and highly intense sunlight. It is preferable to avoid places exposed to variations in the shading, because inhibition induced by dense shade effects (low R/FR ration and consequently low j established) were demonstrated irreversible, and it can lead to undesirable loss of the germination power.

Lettuce pellet seed germination on saline stress conditions

Germination of pelleted seeds of different lettuce cultivars was evaluated. The experimental design used was completely randomized, with four replications, in a factorial outline 5 x 4. Seeds of 'Elisa', 'Veronica AF 259', 'Vera' and 'Tainá' were tested. The sodium chloride (NaCl) concentrations used were 0; 50 Mm(2,9222 g/L); 100 Mm (5,8443 g/L); 150 Mm (8,7665 g/L); and 200 Mm (11,6886 g/L). Germination percentage, germination rate and number of normal seedling were evaluated. The concentration of 200 Mm of NaCl resulted in the lowest number of germinated plants. 'Veronica AF 259' germinated in the shortest time using a concentration of 150 Mn of NaCl.

Storage in cerrado soil and germination of Psychotria vellosiana (Rubiaceae) seeds

The regeneration of plant communities from seed depends, to a large extent, on the capacity of the seed remaining viable in the soil. The viability and germination of artificially buried Psychotria vellosiana seeds in cerrado soil were studied, with the purpose of discovering some physio-ecological aspects of dispersed seeds and evaluating their potential to constitute a soil seed bank. Seed samples were placed in nylon envelopes and buried in the soil of a Cerrado reserve at two different depths and sites. Buried seeds were retrieved periodically and tested for germination along with dry-stored seeds. In general, there was a reduction in seed germination with storage time, both in soil and dry stored conditions, and in some assays exhumed seeds germinated faster than dry stored ones. In general the soil storage favoured seed viability of ungerminated seeds as compared to dry stored ones, with the seeds remaining partially viable after 10 months of storage. The lack of germination of viable seeds suggests that seeds showed true dormancy and/or required an extended time to germinate. It was observed that some seeds had germinated while buried and such in situ germination tended to increase with rainfall. The water availability in the soil might be a limiting factor for successful germination of P. vellosiana in the field, and the seeds may constitute a persistent soil seed bank in the cerrado as dispersed seeds remain viable in the soil until the following period of seed dispersal.

Evaluation of micronuclei frequency in Tradescantia pallida pollen mother cells treated with ethanolic extracts isolated from Cryptocarya mandioccana, Cryptocarya moschata and Pterogyne nitens

Although herbal extracts contain several classes of compounds with pharmacological activity, they also present toxic substances with mutagenic effects. The aim of the present study was to verify the mutagenicity of Cryptocarya moschata, Cryptocarya mandioccana and Pterogyne nitens using micronucleus assay in pollen mother cells (tetrads) in Tradescantia pallida (Trad-MCN). T. pallida inflorescences were treated with different concentrations of ethanolic extracts from the selected plant species. For C. mandioccana C. moschata and P. nitens, Trad-MCN assays were carried out simultaneoulsly, followed by positive control (formaldehyde 10000 ppm), negative control (Hoagland's solution), and vehicle control (Tween 20 20% or DMSO 3%). MCN present in tetrads were quantified in 300 tetrads/inflorescence and the mean (%) and standard error (SE) were established for at least 10 inflorescences per treatment. The extracts demonstrated dose response mutagenicity (clastogenic/aneugenic effects), respectively, C. mandioccana (0.5, 1.0 and 2.0 mg/mL) and P. nitens (1.0 and 2.0 mg/mL) However, no mutagenic effect was observed to C. moschata at the concentrations evaluated in the present study. We can conclude that the C. mandioccana and P. nitens extracts demonstrated clastogenic/aneugenic effects in highest concentrations whereas C. moschata extract did not demonstrate the same effect. © 2006 Sociedade Brasileira de Toxicologia.

Allelopathic effects of aqueous extract of Brassica napus on germination of seeds of Phaseolus vulgaris

Secondary compounds produced by plants are considered an alternative method of weed suppression but can cause negative effects on crops in succession, especially in a no-tillage system, due to the degradation of crop residues with allelopathic potential. The objective of this work was to analyze the influence of foliar aqueous extracts of Brassica napus on the germination and initial development of seedlings of Phaseolus vulgaris. The extract was prepared as a stock 10 % weight/volume solution, and diluted into treatments of relative concentrations of 100 % (i.e. 10 % w/v stock), 75 %, 50 %, 25 % and 0 % (untreated control consisting of distilled water), in a completely randomized design. The seeds of Phaseolus vulgaris were moistened with the differing concentrated extracts and kept in a germination chamber at 25 °C, with a photoperiod of 12 h for nine days. The variables evaluated were: percentage germinating, first count of germination and germination velocity index, as well the root and hypocotyl length, and fresh and dry mass of the seedlings. The aqueous leaf extracts of Brassica napus did not influence the germination of Phaseolus vulgaris seeds, but did induce the growth of abnormal seedlings by inhibition of secondary roots and reduced prominence of the primary root.

Desiccation tolerance in seeds of Annona emarginata (Schldtl.) H. Rainer and action of plant growth regulators on germination

Annona emarginata (Schldtl.) H. Rainer (araticum-de-terra-fria) is used as a rootstock for several species of Annonaceae. It is suggested that these seeds should be sown immediately after extraction and, therefore, they could be intolerant to desiccation. There are several mechanisms involved with desiccation tolerance. Soluble sugars, for example, can accumulate and act as osmoprotectants for the membrane system during desiccation. The aim of this study is to assess desiccation tolerance in A. emarginata seeds. In addition, we examined the soluble sugars involved in desiccation tolerance. Finally, we determined the effect of gibberellic acid (GA4+7) and N-(phenylmethyl)-aminopurine in promoting the germination of seeds with different water contents. The experiment consisted of a randomized 4×5 factorial design (desiccation levels × concentration of growth regulators). After drying, seeds containing 31 (control), 19, 12 and 5% water were incubated in different concentrations of GA4+7 N-(phenylmethyl)-aminopurine (0, 250, 500, 750 and 1000 mg L-1) for 60 hours. The experiment was conducted in a germination chamber with alternating temperature and photoperiod of 20oC for 18 hours of darkness and 30oC for 6 hours of light. We analyzed electrical conductivity, germination rate, mean germination time, germination speed, frequency and uniformity of germination, percentage of dormant seeds and soluble sugar profile in intact seeds through high-performance liquid chromatography (HPLC). The data were subjected to analysis of variance, and the means were compared using Tukey's test at a threshold of p<0.05. The results showed that seeds of A. emarginata appears to be desiccation tolerant and, also, that sucrose increases when seed water content is reduced to values as low as 12%, exogenous GA4+7+N-(phenylmethyl)-aminopurine improves its germinability.