Final Seedling Emergence Research Articles

Emergence and Early Growth of Four Desmanthus Species in Three Alkaline Clay Soils

Tropical pasture legumes such as Desmanthus are expected to improve pasture productivity in the extensive grazing systems of Northern Australia. However, the soils in these areas are often hostile (e.g., hard-setting and nutrient-deficient), which reduces legume emergence and establishment. Furthermore, these soils are often not ameliorated with amendments such as gypsum or starter fertilisers before planting. A pot trial was conducted to investigate differences in the emergence and early growth of four Desmanthus species. The legumes were grown in three alkaline clay soils that were unamended or amended with either gypsum (1 t CaSO4.2H2O ha−1 equivalent), a starter MAP fertiliser (12 kg P ha−1 equivalent), or both gypsum and the starter fertiliser. Seedling emergence was recorded daily and shoot yield was determined after six weeks’ growth. Final seedling emergence (as a percentage of viable seeds) varied among the Desmanthus species (c.f. D. leptophyllus = 63%, D. pernambucanus = 68%, D. bicornutus = 85%, and D. virgatus = 86%). On average, across the treatments, gypsum increased seedling emergence by 15%, whereas the starter fertiliser had no effect. The shoot yields and shoot phosphorus content of the Desmanthus species generally increased in response to the starter fertiliser. The collective results demonstrated that there were differences in emergence and early growth among the four Desmanthus species, which indicates that Desmanthus cultivar selection may be important in the relatively hostile soils of Northern Australia. Gypsum was an effective amendment for seedling emergence, whereas the starter fertiliser was an effective amendment to increase legume productivity.

Chemical seed treatments for the control of cotton seedling damping-off caused by Rhizoctonia solani under greenhouse conditions

Abstract: The aim of this study was to determine the effectiveness of cotton seed treatment with fungicides in the control of seedling damping-off caused by Rhizoctonia solani, under greenhouse conditions. Treated and untreated delinted seeds of the cultivar DeltaOpal were sowed in sand contained in plastic trays, placed in individual and equidistant wells, 3 cm deep. Into each plastic tray were put 3.0 g of the pathogen inoculum. The inoculation of R. solani AG-4 was done by the homogeneous distribution of the fungus inoculum onto the substrate. The fungus was grown for 35 days on autoclaved oat seeds and then ground to powder using a mill (1 mm). Fungicide seed treatments had a significant effect (P ≤ 0.05) on initial and final seedling emergence, pre and post-emergence damping-off, injured seedlings and disease index according to McKinney formula (lesion severity). The best results were obtained by fludioxonil + metalaxyl-M + azoxystrobin, fipronil + pyraclostrobin + methyl-thiophanate, carbendazim + thiram + pencycuron + baytan and carbendazim + thiram + pencycuron + baytan + procymidone. Pearson correlation analysis indicated that injured seedlings and disease index were positively correlated (R = 0.95). This means that the greater the number of injured seedlings, the greater the disease index and the less efficient the fungicide. The fungicides used in the present study did not have any phytotoxic effect on cotton seedlings.

Standardization of vigour test to predict field emergence and difference of seed vigour among lentils (Lens culinaris L.) seed lots

Selecting seeds with high vigour eminently affects initial plant growth and determines plant stand. Various tests including electrical conductivity (EC), radicle emergence counts (RE), and standard germination (SG) tests were used to assess the vigour of eleven lentils (Lens culinaris L.) seed lots. Lentil seed lots with over 75% normal germination, were germinated with the use of an ISTA standard germination test. The radicle emergence (2 mm) was tallied at constant intervals from 24-120 h. The seed lots were sown in the fields and 40 days after sowing, the final seedling emergence was evaluated. The standard germination test demonstrated that there was no substantial correlation between standard germination and field emergence. However, after 24-h of germination, there was a highly significant correlation between seed emergence and radicle emergence count (r = 0.89; p < 0.001). Hence, at 24 h, radicle emergence counts attributed to variations in field emergence by 80%. Results revealed that at 24 h, radicle emergence count during germination could be used as a vigour test to evaluate the full potential of field emergence of lentil seed lots.

Intraspecific differentiation in seed flooding tolerance of Echinochloa crusgalli var. zelayensis population in shores of a giant reservoir along altitudinal gradients

Abstract Aims In a large dam-regulated reservoir with regular hydrological pattern and strong flooding gradients across shore elevations, plants inhabiting in different shore elevations have to confront long-lasting flooding of differential intensities every year. Such persistent stress may lead to intraspecific differentiation of flooding tolerance in seeds. Echinochloa crusgalli var. zelayensis is a dominant annual plant in the shores of the Three Gorges Reservoir (TGR), which plays an important role in the shore vegetation. The objective of this study is to check whether intraspecific differentiation of seed flooding tolerance has occurred among E. crusgalli var. zelayensis populations in the TGR shores and whether such differentiation is associated with weak seed dispersal. Methods We collected seeds of E. crusgalli var. zelayensis from different populations in the TGR shores, and then placed them at four elevations in the shores flooded by reservoir impoundment. Parameters reflecting seed flooding tolerance including post-flooding percentage of intact seeds, seed germinability and seedling emergence rate were investigated for the seeds from different populations and undergoing flooding of different intensities. Floating time of seeds and speed of water level rise during impoundment were examined, and used to quantify dispersal potential of seeds in the shores of the TGR when flooded. Important Findings Both intact seed percentage and final seedling emergence rate after flooding significantly declined with increasing shore elevations where the seeds were collected, indicating that intraspecific differentiation in seed flooding tolerance has occurred among E. crusgalli var. zelayensis populations in the TGR shores after 7-year operation of the reservoir. The distance of seeds transported by rising water during reservoir impoundment was limited due to short-floating time of the seeds and relatively low speed of water level rise in the reservoir. This would be favourable to the development of intraspecific differentiation in seed flooding tolerance.

Single radicle emergence count for predicting vigour of marigold (Tagetes spp.) seed lots

This study was carried out to determine whether a single radicle emergence count (RE) during germination can be used for vigour assessment to estimate field emergence of marigold (Tagetes spp.) seed lots. Six marigold seed lots (Tagetes erecta and T. patula) with normal germination above 75% were germinated using the standard ISTA germination test and radicle emergence (production of 2 mm radicle) counted at regular intervals from 25 to 169 hours. The seed lots were also sown in the field with final seedling emergence assessed after 25 days. Seedling emergence was highly correlated with the radicle emergence count after 49 and 66 hours germination (r = 0.90 and r = 0.91, respectively; P &lt; 0.01) but not with germination percentage (r = 0.26). Thus, the radicle emergence counts at 49 and 66 hours accounted for 81 or 83% of the variation in field emergence, respectively. The results indicate that a 49- or 66-hour count of RE during germination could be used as a vigour test to estimate field emergence for marigold seed lots.

Non-native Mammals Are the Main Seed Dispersers of the Ancient Mediterranean Palm Chamaerops humilis L. in the Balearic Islands: Rescuers of a Lost Seed Dispersal Service?

Megafauna extinctions often lead to the disruption of plant-animal interactions, such as the seed-disperser mutualisms, which might entail severe consequences for plant populations and entire communities. Interestingly, the contemporary persistence of anachronistic plant species might be possible thanks to surrogate dispersers or seed dispersal “rescuers”. We know very little on how these relevant functional replacements are contributing to the performance of present-day plant-frugivore networks. The dwarf palm Chamaerops humilis L. is a Mediterranean endemism with fleshy fruits and typically dispersed by mammals. Despite its ecological importance and wide distribution in some of the Mediterranean islands, no information exists about its seed dispersal on these depauperated-fauna systems. In this study, we aim at identifying and quantifying the relative importance of introduced frugivores on the island of Mallorca (Balearic Islands), where no native terrestrial mammals exist. Specifically, we assess for the first time the seed dispersal effectiveness (SDE) for C. humilis on islands; we evaluate the quantitative component by fecal and regurgitation sampling surveys, and the qualitative component by means of seed germination experiments and seedling growth measures. Introduced goats (Capra hircus L.) and pine martens (Martes martes L.) were the local mammal fruit consumers of C. humilis identified in our study sites. Results suggest that goats are much more important quantitatively than pine martens, due to the high number of fruits handled in each foraging bout and their extremely high abundance on the island. However, pine marten-ingested seeds showed the highest final seedling emergence success and seedling growth, thus its qualitative contribution on C. humilis seed dispersal is higher than that of goats. Overall, SDE was almost 9-fold higher for goats than for pine martens. We conclude that these two non-native mammal species are effective seed dispersers of C. humilis in this and probably other Mediterranean islands, where humans led to the extinction of its native seed dispersers, as it was probably the case of the goat-like Myotragus balearicus in the Balearic Islands.

Adequacy of the tetrazolium test methodology for Stylosanthes capitata Vogel seeds

Abstract: The seed sector is increasingly dynamic and therefore demands rapid decision-making. The tetrazolium test is a rapid test that determines the viability of seeds, especially from species that show slow germination or dormancy. The methodology described in the Rules for Seed Testing for Stylosanthes sp. is not applied effectively to the Stylosanthes capitata Vogel species. Three seed lots of S. capitata seeds with different quality levels were used to fit the tetrazolium test methodology. In order to determine the physiological quality of seeds, the tests of germination, first count germination, emergence speed index, initial and final seedling emergence percentage, electrical conductivity, respiratory activity and seed moisture content were performed, besides the imbibition curve for the establishment of pre-imbibition periods of the seeds to perform the tetrazolium test. The pre-imbibition and staining periods of 6, 12 and 18 h, and 3, 6, 12 and 24 h at concentrations of 0.075%, 0.1% and 0.5% tetrazolium solution were tested. It was concluded that the 12-h pre-imbibition period and 6-h staining at the 0.1% tetrazolium solution is ideal for evaluating the viability of S. capitata seeds.

Physiological potential of soybean seeds over storage after industrial treatment

Abstract: The aim of this study was to evaluate the effect of industrial seed treatments on the physiological potential of soybean seeds over storage. Four mixtures of agrochemical products in association with two fertilizers were tested. The agrochemical product mixtures were carbendazim/thiram + imidacloprid/thiodicarb; pyraclostrobin, thiophanate-methyl, and fipronil; thiophanate-methyl/fluazinam + bifenthrin/imidacloprid; and metalaxyl-m/fludioxonil + thiamethoxam. The two fertilizers were 7% N, 16% P2O5, 0.6% Co, and 2.5% Mo; and 1% Co, 10% Mo, and 7% P2 O5. The experiment was carried out in a completely randomized design in a split-plot arrangement in time, with four replications. The treatments were allocated in the plots, while the storage periods (0, 30, 60, 90, and 120 days) constituted the split-plots. The following tests were carried out in each period: first count of germination, germination, accelerated aging, emergence speed index in sand substrate, and final seedling emergence in sand substrate. Seed germination and vigor declined over the storage period, especially after industrial treatment. Pesticide mixtures of a carbendazim/thiram fungicide base and an imidacloprid/thiodicarb insecticide base most impaired seed physiological potential throughout storage, regardless of fertilizer use in the industrial treatment.

The effect of simulated damage by weevils on Quercus ilex subsp. Ballota acorns germination, seedling growth and tolerance to experimentally induced drought

Abstract The main aim of this study is to assess the effect of moderate to low level of cotyledon damage (simulated weevils infection) on holm-oak seedling growth and physiological performance under conditions of soil water stress, a recurrent constraint in Mediterranean and other seasonally dry environment. Three levels of artificial damage were applied to the acorns (no damage NoD, low damage LD, and medium damage MD), and the germination, emergence and early seedling growth under controlled conditions were studied during ca. 1.5 months. On the other hand drought effect on seedling growth, leaf gas-exchange, PSII efficiency, photosynthetic pigments and electron transport energy fluxes was analyzed in a set of older seedlings (i.e., 6.5 months old) that also derived from treated acorns and were exposed to two irrigation treatments (well water WW and water stress WS) for 1.5 months. The results showed that LD and MD acorns germinated earlier than NoD ones but final seedling emergence was lowest in the MD treatment. Cotyledons exhibited increased level of necrotic tissue as physical damage (drilling) increased while seedling biomass and size-related traits tended to decrease. Under WS conditions seedlings derived from LD and MD exhibited higher decrease in above and belowground biomass, as well as on net photosynthetic rate (AN), stomatal conductance (gs), intercellular CO2 concentration (Ci) and PSII efficiency than those derived from NoD. These differences were much less conspicuous under WW treatment where all traits reached higher values. In view of the interactive effect of drought and acorn damage it is concluded that under natural conditions acorn infection by weevils and other insects may represent a highest limitation to holm-oak seedling recruitment than previously considered. In addition this limitation may become more important in the future whether warming and drought increase.

English

Thiamethoxam is a neonicotinoid insecticide, which is believed to induce the expression of enzymes and proteins that activate plant defense mechanisms, thus improving the plant resistance to stress factors. The aim of this study was to evaluate the physiological performance of melon and watermelon seeds treated with thiamethoxam. The seed treatment consisted of five doses of thiamethoxam, 0, 2, 4, 6 and 8 mL per kilogram of seeds. The parameters evaluated were measured by a standard germination test, first count of germination test, laboratory vigor tests (accelerated aging and cold tests), and a field vigor test (seedling emergence). Thiamethoxam treatment resulted in increase in the normal seedling percentage in the standard germination, first count of germination, accelerated aging, cold and final seedling emergence tests. The doses of 4.0 to 5.0 mL of thiamethoxam per kilogram of seeds were most efficient in improving the physiological performance of melon and watermelon seeds. Key words: Thiamethoxam, seedling vigor, Cucumis melo, Citrullus lanatus.

Relationship between laboratory indices of soybean seed vigor with field emergence and yield

This study was conducted for evaluation the correlation of laboratory seed quality indices with field emergence in 2013. First the standard germination test and seed vigor tests were conducted for of two cultivars (Williams and L17) which were produced in last year and also recent year and germination percent and seedling vigor index were measured. Then vigor tests including cold and accelerated aging tests were conducted. The laboratory experiments were done as a factorial experiment with two factors based on completely randomized design in 4 replications and field experiment was as a factorial experiment with two factors based on randomized complete block design in 4 replications. According to results germination percent and seedling vigor index had a high correlation with final seedling emergence percent and cumulative emergence rate. The seedling vigor index in cold test specified the highest correlation with final seedling emergence percent (r= 0.941) and cumulative emergence rate (r=0.756). The correlation of laboratory traits and yield related traits defined that standard germination percent (r=0.756) and seedling vigor index (r=0.711) in cold test showed a high correlation with final yield and the related traits to accelerated aging test had a lesser correlation.

Response of Sugar Beet to Salinity during the Stages of Seedling Emergence and Plant Growth

The effect of NaCl on seedling emergence, plant growth and ion accumulation for two sugar beet cultivars was evaluated. The result showed that seedling emergence in Tianyan309 was much lower than that in KWS3418 in the initial 6 days. High salinity markedly decreased final seedling emergence in both cultivars, especially in Tianyan309, while salinity had no adverse effect on total seedling emergence after the recovery experiment in both cultivars. Low salinity (86 mM NaCl) had no significant effect on shoot and root dry weights, while 171 and 257 mM NaCl inhibited shoot and root dry weights of two cultivars, especially for KWS3418. Concentrations of Na+ and Cl- in leaves were increased with increasing NaCl in both cultivars. There was no significant difference between two cultivars in concentrations of Na+ and Cl- in the leaves at different concentrations of NaCl, except that Cl- concentration in leaves of Tianyan309 was lower than that in KWS3418 at 257 mM NaCl. The characteristic of Cl- uptake and/or accumulation may relate to different salt tolerance of KWS3418 and Tianyan309.

Seedling emergence response to early sowings in unprimed and osmoprimed seeds of fiber sorghums for energy biomass under semi-arid climate

Fiber sorghum is a promising industrial crop for lignocellulosic biomass to be used for energy purposes. Limits to the adoption of early sowings (March-April) for this species are found in its thermal requirements for seed germination (&gt;10°C). Seed osmopriming has been found to decrease the impact of low temperatures on seed germination of sorghum in laboratory. In this study, unprimed (UP) and primed (P) seed germination behavior in both laboratory at cold temperatures and open field conditions under early sowing in a typically Mediterranean environment, was examined in four cold-tolerant cultivars of fiber sorghum (Padana 4, PR 811F, Jumbo and PSE 24213). Seed germination in UP at 8°C was on average 82.4%, confirming the high cold-tolerance of all cultivars selected for the experiment. Germination was progressively delayed by the lowering of temperature from 25°C to 8°C. Seed osmopriming was effective in promoting germination speed at all temperatures in laboratory. It also resulted in an appreciable lowering of thermal time requirements for final germination. With the earliest planting date (March 10), minimum soil temperatures during the first ten days never dropped below 10.2°C, allowing a final seedling emergence of 79.2% in UP. However, low soil temperatures slowed down the rate of seed germination. At the 2nd sowing (end of March), daily maximum temperatures of soil exceeded 20°C but those minimum dropped below 10°C, slightly depressing seed germination in UP (76.3%). With the latest sowings (mid-April and early May), minimum soil temperatures always over exceeded minimum threshold for seed germination, allowing a regular seed germination in UP. Priming increased final emergence percentage in the two earliest sowings (those of March), whilst it enhanced the germination speed in all planting dates. Seed osmopriming also reduced thermal time requirements until the first seedling emerged from soil and promoted the seedling growth in all cultivars and sowing dates. These results suggest that it is possible to adopt early sowings (March) in cold-tolerant cultivars of sorghum under semi-arid climate, and that osmopriming allows the seed to partially overcome the limit imposed by cold soil to germination, contributing to a successful crop establishment when early plantings are adopted. Although the germination response to constant low temperatures in laboratory tests does not always provide a good index for predicting seedling emergence in soil under fluctuating uncontrolled temperatures, it may contribute to define desirable attributes for the identification of cultivars adapt to early sowings in the Mediterranean areas.

Effect of halopriming on germination and seedling vigor of tomato

The study was carried out to investigate the effects of halopriming on germination, seedling growth and biochemical responses of tomato seeds. Priming was done by exposing seeds of two tomato cultivars ‘Nagina’ and ‘Pakit’ to aerated solutions of 10, 25 and 50 mM NaCl and KNO3 for 24 h. Halopriming with 25 mM KNO3 increased final germination percentage, germination index, root length, shoot length and seedling fresh weight of both tomato cultivars as compared to all presowing seed treatments including control. Seeds of both tomato cultivars primed with 25 mM KNO3 for 24 h, significantly reduced the time taken to 50% emergence and mean emergence, increased final seedling emergence percentage and seedling growth. Results indicated that halopriming with varying concentrations of KNO3 improved germination potential and seedling establishment of both cultivars and it proved better option than NaCl which resulted in poor emergence and seedling growth. Maximum improvement was recorded in seeds primed with 25 mM KNO3. The better performance of haloprimed seeds may be due to lower electrical conductivity (EC) of seed leachates, higher total and reducing sugars along with increased α-amylase activity. Key words: Seed dormancy, α-amylase, halopriming, electrical conductivity, reducing sugars.

Desempenho fisiológico de sementes de algodoeiro tratadas com tiametoxam

Novos produtos para incorporação às sementes vêm sendo disponibilizados anualmente. Bioativadores, como o inseticida tiametoxam, são utilizados para aumentar o potencial produtivo das plantas, através de modificações no metabolismo vegetal. Objetivou-se neste trabalho avaliar os efeitos do tiametoxam na qualidade fisiológica de sementes de algodoeiro, particularmente no crescimento radicular de plântulas de algodoeiro e estabelecer concentrações do produto para pré-tratamento de sementes. Foram utilizados três lotes de sementes de algodoeiro, cultivar CD 408, tratadas com Cruiser® 350 FS contendo 35 gramas de ingrediente ativo (i.a.) de tiametoxam por litro, sendo, submetidas a seis doses: 0, 2, 4, 6, 8 e 10 mL de Cruiser® 350 FS/kg de semente. As avaliações utilizadas foram: germinação, primeira contagem de germinação, envelhecimento acelerado, comprimento e massa de matéria seca do sistema radicular, índice de velocidade de emergência e emergência final de plântulas. O tratamento de sementes de algodoeiro com tiametoxam favorece positivamente a qualidade fisiológica das sementes, e as doses de 5,0 a 7,0 mL de Cruiser® 350 FS/kg de semente mostram-se mais eficientes em melhorar o desempenho fisiológico das sementes de algodoeiro.

Foliar application of zinc and manganese improves seed yield and quality of safflower ( Carthamus tinctorius L.) grown under water deficit stress

Information regarding the effect of foliar application of zinc and manganese on the growth and development of safflower under water deficiency is not available. Therefore, field experiments were conducted in 2001–2002, 2002–2003 and 2004 (as the field emergence experiment) to determine agronomic traits and seed quality of safflower under above-mentioned conditions. Irrigation treatment (unstressed control, and withholding irrigation during vegetative growth, flowering and seed filling stages), safflower genotype (Zarghan 279, Varamin 295 and L.R.V.5151) and foliar application treatment (untreated plots, foliar application of water, zinc sulfate and manganese sulfate) were studied in a split factorial design with three replications, with irrigation treatment as the main plot, and factorial combination of the other two factors as the subplot. Generally there was a decrease in seed yield, total biomass, number of capitula per plant and plant height each growing season by withholding irrigation at various growth stages at all treatment combinations, especially when water deficit stress was imposed at the flowering stage. The foliar application of Zn, Mn and in some cases water mitigated the negative effect of water deficit stress on agronomic traits in all three genotypes. Averaged over 2001–2002 and 2002–2003, without foliar application, Zarghan 279 was found suitable for unstressed conditions and appeared to grapple better with water deficit stress during vegetative growth stage and L.R.V.5151 showed a better ability to recover from stress at the flowering and seed filling stages. Foliar application of Zn and Mn increased concentration of these two elements in seed, germination rate, germination percentage, seedling dry weight and final seedling emergence, and water deficit stress had negative impacts on most these parameters. All treatments had significant effects on proteins and the major protein fractions of safflower were the albumins (20–37 mg g −1) and globulins (15.7–36.3 mg g −1). With regard to oil content and its composition, small differences were evident between treatments. Linoleic acid and oleic acid comprised about 90% of the fatty acid composition. In general, significant relationships existed between traits. The results obtained here suggest that foliar Zn and Mn application can improve the seed yield and seed quality of safflower grown under drought stress.

Bioregulator application, agronomic efficiency, and quality of soybean seeds

The application of vegetal bioregulators has shown promising results, mainly in cultures that have already reached a high level of technology. Based on this context an experiment was carried out with the objective of evaluating agronomic traits of plants, such as yield and quality of seeds, produced by applying bioregulators to a soybean crop. For this purpose, the following treatments were carried out: before sowing - seed treatment (25, 50 and 75 mL for 100 kg-1 seeds); during sowing time - spraying on the sowing lines (pulverization onto the sowing lines) (50, 100 and 150 mL ha-1); between stages V5 and V6 (25, 50 and 75 mL ha-1); and the control - no treatment. Emergence speed, final seedling emergence, number of pods and seeds per plant, average height of plants, first pod insertion height, duration of the cycle, final stand, degree of plant layering, and the yield and weight of one thousand seeds were evaluated. The quality of seeds was evaluated based on germination, classification of seedling vigor, tetrazolium, health test and the quantity of oil and protein tests. The highest yield of grains, an increase of 92% as compared to the control, was obtained when using the product at a dose of 75 mL ha-1. The best quality seeds and the highest oil and protein content were obtained from seeds produced by plants whose seeds were treated before sowing time using the bioregulator (75 mL for 100 kg-1 seeds).

Efeito do tratamento de sementes de algodoeiro com fungicidas no controle do tombamento de plântulas causado por Rhizoctonia solani, sob condições de casa de vegetação

O objetivo deste trabalho foi avaliar a eficacia do tratamento de sementes de algodoeiro com fungicidas no controle do tombamento de plântulas causado por Rhizoctonia solani. O ensaio foi conduzido na casa de vegetacao da Embrapa Agropecuaria Oeste, em Dourados, Mato Grosso do Sul. Sementes nao tratadas e tratadas com os fungicidas foram semeadas em areia contida em bandejas plasticas, dispostas em orificios individuais, equidistantes e a 3 cm de profundidade. A inoculacao com R. solani AG-4 foi feita utilizando-se 5g do inoculo do fungo/bandeja, distribuidos de forma homogenea na superficie do substrato. O fungo foi cultivado por 35 dias em sementes de aveia preta autoclavadas e trituradas em moinho (1mm). Foi observado efeito significativo do tratamento fungicida na emergencia inicial e final de plântulas, bem como no controle do tombamento de pre e pos-emergencia do algodoeiro, com os melhores resultados sendo obtidos pelos tratamentos tolylfluanid+pencycuron+triadimenol e azoxystrobin+fludioxonil+mefenoxan, seguidos de carboxin+thiram, PCNB e pencycuron. O fungicida menos eficiente foi o carbendazim+thiram. Melhores resultados com relacao as variaveis estudadas foram obtidos com a utilizacao de misturas de fungicidas em comparacao ao uso isolado de um determinado produto. Nao foram observadas diferencas significativas com relacao ao indice de velocidade de emergencia, altura e peso fresco das plântulas.

The efficacy of different seed priming osmotica on the establishment of maize (Zea mays L.) caryopses

The purpose of this Communication is to compare the efficacy of different seed priming osmotica on the germination and emergence of maize caryopses. First, a laboratory experiment was carried out to determine the effects of different seed priming osmotica on germination. The osmotica used are 0.1% copper sulphate, 0.1% zinc sulphate and 0.1% sodium sulphate. A control of unprimed caryopses was used for comparative analysis. In general, seed priming significantly increased the final caryopses germination. Caryopses primed in copper sulphate, however, gave the highest final germination. Then, field trials to determine the final seedling emergence of caryopsis in the field were carried out in a semi-arid area in southern Zimbabwe. Results testify that priming in copper sulphate and zinc sulphate significantly increased seed emergence by 43% and 29%, respectively, while priming in sodium sulphate did not significantly increase emergence. The study thus recommends copper sulphate as the most suitable seed priming osmotica.

Seed mass effects on performance of Pinus halepensis Mill. seedlings sown after fire

Pinus halepensis is a widely distributed species in the Mediterranean basin. It is generally well adapted to regenerate after wildfire, except when fire intervals are too short (≤15 years). In these latter situations, direct seeding could be a good alternative for restoring pine woodland after fire. Under dry climate, low seedling growth and survival can greatly limit the use of seeding. Early studies have shown that seedlings grown from large seeds have higher seedling establishment, growth and survival. Seed size grading may however reduce the genetic diversity of a seed lot by eliminating part or all of the families with relatively small seeds. An alternative to improve seed lot quality without losing genetic variability could be collecting and sieving seeds from each family separately. In order to explore the influence of seed mass on P. halepensis seedling performance, seeds from five half-sib families differing in mean seed mass were sown under greenhouse and field conditions. Final seedling emergence was unrelated to seed mass and half-sib family. The time of emergence was also unrelated to seed mass but it varied among families. Seed mass showed a positive effect on seedling height and diameter, both at population level and within family throughout the study period (9 months under greenhouse conditions and 20 months under field conditions). We also observed a negative relationship between seed mass and relative growth rate for seedling diameter, but it was not high enough to fully compensate the initial differences due to seed mass at the end of the 20-month study period. Seedling predation had a considerable impact on seedling survival, and it was not related to seed mass. When seedlings killed by predation were excluded from the survival analysis, larger seedlings, coming from larger seeds, showed slightly better survival, but only during the first growing period. The small advantages obtained from large seed mass in seedling development do not seem to justify the increased operational costs derived from seed mass selection for each family.