Initial Seedling Establishment Research Articles

Seed thermo-priming accelerates the growth of Ceiba glaziovii (Kutze) K.Schum. seedlings

Background: Global climate changes have caused temperature increases that can harm plant development, especially the initial growth and establishment of seedlings for the recovery of degraded areas. However, there are species in which these losses are attenuated when the seeds are thermo-primed to sublethal temperatures. Therefore, the objective of the present study was to evaluate the influence of seed heat conditioning on germination and initial growth of Ceiba glaziovii (Kuntze) K. Schum seedlings, an endemic species occurring in seasonally tropical dry forest in Brazil. Methods: Seeds of C. glaziovii were exposed to 70 oC for 15, 30, 45, 60 and 90 minutes as pre-germination treatments. The control did not undergo heat treatment. Germination variables, vegetative growth, survival rate and normal leaves were evaluated. Results: Thermo-priming negatively affected the germination proportion of C. glaziovii seeds with increasing exposure time. However, it significantly enhanced vegetative growth and seedling survival rate of this species after transplanting, without impairing the formation of normal leaves. Conclusions: Thermo-priming of seeds was found to produce more vigorous seedlings of Ceiba glaziovii.

Regenerative strategies of Euterpe edulis (Arecaceae) at its altitudinal limits in the Atlantic Forest

AbstractPopulations occurring at the limit of a species' altitudinal distribution undergo strong environmental filtering. Rapid climate change intensifies this process, impacting ecological responses of populations. Understanding the effects of climate change, especially in the early stages of plant development, has become essential to predict vulnerability to extinction. However, few studies have explored initial establishment strategies of plant populations at the limit of their distribution in the face of global warming. We tested the effects of increasing temperatures on germination performance and on initial seedling establishment on two populations of Euterpe edulis, a palm tree widely distributed in the Atlantic Forest between 0 and 1400 m altitude. The tests were conducted in a laboratory, where the seeds were exposed to three conditions for 90 days: control at 25°C, and two treatments at higher temperatures (35 and 40°C). Germination percentage was not affected by population, seed size class or treatments. Average time for germination only increased in the Montane Forest population in the most extreme treatment, while in the sea level Restinga population, time for germination was affected by a small temperature increase. Mortality percentage in the Restinga population was similar in the post‐germination phase and in the temperature treatments. We concluded that E. edulis populations located at their lower altitudinal limit are closer to the species thermal limit, thus being more vulnerable to temperature increase than populations at the upper limit of the species' altitudinal distribution.

Primary succession of ectomycorrhizal fungi associated with Alnus sieboldiana on Izu-Oshima Island, Japan

The primary succession of ectomycorrhizal (ECM) fungi has been well described for Pinus and Salix, but the succession for other pioneer hosts is almost unknown. Here, we investigated ECM fungal communities of Alnus sieboldiana at different host growth stages in a primary successional volcanic site on Izu-Oshima Island, Japan. ECM root tips were collected from 120 host individuals, encompassing seedling, sapling, and mature tree stages. The taxonomic identity of the ECM fungi was determined based on rDNA internal transcribed spacer region sequences. Nine molecular taxonomic units were detected from a total of 807 root tips. The initial ECM fungal community on the pioneer seedlings was composed of only three species, where an undescribed Alpova species (Alpova sp.) was exclusively frequent. With host growth, other ECM fungal species were added to the communities, while the initial colonizers remained even at mature tree stages. Thus, the ECM fungal composition significantly changed along host growth stages and showed the nested community structure. Although most of the ECM fungi confirmed in this study had a broad Holarctic geographical distribution, the Alpova sp. had no previous records in other regions. These results suggest that a locally evolved Alpova sp. plays an essential role in the initial seedling establishment of A. sieboldiana at early successional volcanic sites.

Siphoning novel sources of seedling salinity tolerance from the diverse chickpea landraces

Context Chickpea (Cicer arietinum L.) are highly sensitive to elevated salinity, particularly at initial seedling establishment stage. Seedling screening would be an effective means to identify novel sources of donors for salt tolerance. Aim This study aimed to identify salt stress tolerant genotypes at seedling stage from 50 chickpea accessions. Methods The screening of 50 chickpea accessions was done under two salinity conditions including salt stress (8 dS m−1) and control (no salt stress). Accessions were studied for morphological traits, root system architectural analysis, and CSTI (Cumulative salt tolerance index). Further, principal component analysis was conducted to validate these results for more accuracy and reliability. Key results For morphological traits, a high degree of genetic variation was seen among genotypes, and root traits were found to be the better indicators of salt stress tolerance. CSTI was used to classify the accessions; 22 (44%) were identified as salt sensitive, 21 (42%) were found to be moderately salt tolerant, and 7 (14%) had moderate to high salt tolerance. The most salt tolerant and salt sensitive genotypes were found to be ICCV10 and ILC5595, respectively. Conclusions Early seedling screening has a great potential to identify genotypes with robust root systems, which can withstand salinity. Implications We used a novel approach to classify chickpea landraces based on the combination of CSTI and principal component analysis methods. By choosing suitable donors and prospective genotypes at early growth stages, the knowledge gathered from this study may aid scientists and chickpea breeders in developing salt tolerant cultivars.

Ajuste da densidade de semeadura de arroz pelo vigor de sementes

ABSTRACT The use of high-vigor seeds combined with seeding density adjustment at sowing is speculated to ensure high yields. However, certain doubts regarding the effect of this combined approach on rice cultivation remain owing to the tillering capacity. In this context, the present study aimed to determine the effects of seeding density adjustment according to vigor on the initial establishment of seedlings in the field. A physiological characterization was conducted using the germination test, vigor by accelerated aging, electrical conductivity, first count, shoot length, root length, total seedling length, and dry mass in the 2019/2020 and 2020/2021 growing seasons. The evaluations were conducted using a completely randomized design with four replications. Subsequently, the seed lots were selected, from which a fraction of seeds were submitted to artificial vigor reduction. Afterward, these seeds were sown in the main producing regions of the state of Santa Catarina, under a randomized block design with four replications. Three treatment groups were formed: one without density adjustment, one with adjustment by germination, and one with adjustment by vigor in accelerated aging. Twenty-one days after sowing, the number of emerged seedlings per unit area was determined. An interaction between the factors of adjustment for density and seed quality was observed. This was evidenced in the fact that even with the adjustment of density by vigor, the seed lot with lower quality presented the emergence of a lower number of seedlings, and the performance of these seeds was not equivalent to that observed in the lot with superior quality. Accordingly, it was concluded that the seeding density adjustment by vigor combined with the use of seeds with high-vigor is a suitable strategy for achieving a significant increase in plant emergence during the initial establishment in the field.

Non-thermal plasma application improves germination, establishment and productivity of Gatton panic grass (

Megathyrsus maximus (Gatton panic) is a tropical grass highly valued both for its use as forage and for its biofuel potential. A major constraint in establishing pastures of this cultivar is the low viability and germination of seeds and the poor initial seedling establishment. We used non-thermal plasma (NTP, partially ionised gas) as a novel technology to treat seeds of this grass, aiming to improve their quality (i.e. germination traits). We also followed the performance of seedlings grown from NTP-treated seeds under field conditions by assessing seedling establishment, biomass production and forage quality during the first regrowth period, which is the critical period for pasture establishment. Two NTP treatments were performed through dielectric barrier discharges employing N2 as carrier gas. Non-treated seeds served as the control. Results showed that the viability of NTP-treated seeds was, on average, 1.5-fold higher than the control, and that germination energy and germination percentage of treated seeds was superior to the control by 2.1-fold and 2.2-fold, respectively. A field experiment showed that seedling establishment parameters (dynamics of cumulative emergence, emergence coefficient, and weighted average emergence rate) and pasture early productivity (represented by shoot dry matter) were enhanced by NTP treatment (phenolic sheet–polyester film barrier and 3 min exposure), showing 1.4–2.6-fold higher values than the control, confirming the results of the laboratory assays. Although NTP markedly increased the shoot dry matter production of the pasture, which was related to higher tiller population density and greater tiller weight, it did not affect the forage quality of the plants grown in the field. We conclude that NTP technology is suitable to improve seed germination of Gatton panic, in turn leading to improvements in seedling establishment and biomass production under field conditions without compromising forage quality.

Type of container and Trichoderma spp. inoculation enhance the performance of tree species in enrichment planting

Complementary techniques such as enrichment plantations are used in increasing the diversity of understory of forests undergoing restoration. The choice of suitable species and the development of strategies capable of enhancing the initial establishment of seedlings are crucial for its success. Thus, we aimed to characterize the performance of five native tree species in an enrichment plantation in the extreme south of the Atlantic Forest Biome and identify the effects of substrate volume used in the production of seedlings and Trichoderma spp. inoculation on survival, initial growth, and physiology of planted species. The species used were Cabralea canjerana, Cedrela fissilis, Cordia trichotoma, Erythrina cristagalli, and Luehea divaricata. The experiment was conducted in a 2 × 3 factorial scheme, and the factors are types of containers used in the production of seedlings (180 cm polypropylene tubes and 1500 cm3 polyethylene bags) and three inoculants (control, Trichoderma asperelloides, and Trichoderma harzianum). The seedlings were planted between the lines of mixed plants, in a randomized block design with four replicates. We evaluated survival, the increase in height and diameter of collected seedlings, content of photosynthetic pigments, and the fluorescence of chlorophyll a. The studied species showed satisfactory survival and growth rates at 15 months after planting, indicating that it is able to affect enrichment plantations in areas undergoing restoration in the extreme south of the Atlantic Forest Biome. In enrichment practices, the survival and morphophysiological aspects of the species evaluated were not affected by type of container, suggesting a 180 cm3 polypropylene tube for seedling production. The use of T. asperelloides benefits the physiology and growth of C. canjerana, C. fissilis, and C. trichoma, and is an important tool for enhancing its development in fields.

Effect of Bacillus aryabhattai on the initial establishment of pre-sprouted seedlings of sugarcane varieties

This study proposes to examine the potential use of Bacillus aryabhattai in pre-sprouted seedlings of sugarcane inoculated with the microorganism when subjected to different regimes of water supply after transplanting. The experiment was laid out in a randomized-block design with a complete 3 × 2 × 5 factorial arrangement, in five replicates. The factors were represented by pre-sprouted seedlings of three sugarcane varieties (IAC 911099, RB 855156 and CTC 20), two seedling types (inoculated and not inoculated with B. aryabhattai) and five frequencies of water supply, which provided the ability of return to 100% soil field capacity, at every 0, 10, 20, 30 and 40 days. Plant mortality, plant height, number of leaves, stalk diameter and number of tillers were evaluated throughout the experimental period. At the end of the study, the shoot dry matter (SDM) and root dry matter (RDM) contents of the plants were measured. The number of leaves on the plant was affected only in isolation, according to the cultivar, without effects of the other studied factors. There was a double interaction effect between the factors of variety and inoculation (V*I) for the variables of SDM, stalk diameter and height; and between frequency and inoculation (F*I) for stalk diameter. There was a triple interaction effect between variety, inoculation and frequency (V*I*F) for the RDM variable. Thus, the use of B. aryabhattai as an inoculant in pre-sprouted seedlings of sugarcane at the time of seedling formation can improve plant development after transplanting depending on the cultivar used, especially in IAC 911099 and RB 855156.

Light sources on the germination and initial in vitro establishment of Schomburgkia crispa Lindl., a species of the Brazilian Cerrado

ABSTRACT: Light is one of the factors that influence the germination and initial establishment of orchids under in vitro cultivation. This study evaluated the effect of different light sources on these stages in in vitro cultivation of Schomburgkia crispa Lindl. After sowing in an aseptic environment, we stored the cultures in a screened greenhouse (natural light) or in a growth room with the following light sources: 3,000 K yellow LED; 6,500 K white LED [1]; 6,500 K white LED [2]; or 6,500 K white fluorescent lamp (control). We assessed germination percentage and initial seedling establishment at 45 and 90 days after sowing. Light did not influence the germination of S. crispa. However, the use of 3,000 K LED provided a faster initial establishment of S. crispa when compared to the other light sources, also presenting lower seedling mortality. Thus, the light source 3,000 K LED is a potential substitute for the 6,500 K fluorescent lamps and LEDs used in growth rooms in in vitro culture laboratories.

Soil moisture strongly limits Douglas-fir seedling establishment near its upper elevational limit in the southern Rocky Mountains

Climate change is causing significant shifts in tree species distributions to higher elevations and latitudes. Seed germination and seedling establishment are particularly important steps in tree range expansion under warmer conditions, yet seedling establishment is influenced by a range of factors beyond temperature, including herbivory, microenvironment, and the timing and amount of precipitation. We conducted an experiment to assess how augmented precipitation regimes, wildlife herbivory, and microclimate influence germination and first-season survival of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) near the upper elevational limit of its range in the southern Rocky Mountains. Germination was strongly influenced by moisture, with over three times higher germination in watered treatments. Seedling survival was similar across watered treatments but was negatively associated with microenvironments with higher maximum temperatures. These results indicate that soil moisture effects on germination and the negative impact of hot growing-season temperatures on seedling survival limit initial seedling establishment in Douglas-fir, even at the cooler and wetter end of its range, suggesting that the planting of this species will be most successful in cooler and wetter microsites. Taken together, this study suggests that continued warming and projected increases in droughts may strongly limit Douglas-fir regeneration and thus its ability to shift upwards with climate change.

Does Azospirillum brasilense and biostimulant improve the initial growth of rice sown at greater depths?

The sowing operation is crucial for the proper initial establishment of seedlings and their development. However, there is a lack of studies about the effects of sowing depth of rice, as well as technologies that aid to mitigate the prejudicial effects caused by depth. In this way, the present work aimed to evaluate the initial growth of rice plants inoculated with Azospirillum brasiliense and treated with biostimulant sowed at different depths. Randomized complete block design with four replications was used, in a 4 × 4 factorial scheme. The first factor was composed of different seed treatments (a, control—without treatment; b, inoculation with A. brasilense; c, seed treatment with Stimulate® and d, inoculation with A. brasilense associated with seed treatment with Stimulate®). The second factor was composed of four sowing depths (1.0, 3.0, 5.0 and 7.0 cm). Treatment of rice seeds with A. brasilense and Stimulate® decreases the rate of emergence. The sowing at 7 cm depth decreases in 41.44% of the emergence, when compared to sowing at 1 cm. Inoculation with A. brasilense and sowing at increasing depths are prejudicial to the growth of rice crop.

Windows of opportunity for smooth cordgrass landward invasion to tidal channel margins: The importance of hydrodynamic disturbance to seedling establishment

Despite increasing concerns about the global threat of cordgrass (S. alterniflora) expansion and the interest in its invasion mechanisms, there is not yet a general understanding of the mechanistic processes underlying the interaction between cordgrass invasion and geomorphic structures such as tidal channels. This study elucidated the effects of the hydrodynamic disturbance of tidal channels on initial seedling establishment of cordgrass in the margins of two different types of tidal channels (i.e., main tidal channels and secondary tributaries). We performed field experiments that transplanted cordgrass seedlings to above-mentioned tidal channel margins with on-site controlled hydrodynamic conditions. The results showed that high hydrodynamic disturbance intensity (i.e., HDI) on the margin of main tidal channels (i.e., MMC) was not beneficial to cordgrass invasion, whereas low HDI created windows of opportunity for cordgrass invasion to the margin of secondary tributaries (i.e., MST) by facilitating the survival, growth, and stability of cordgrass seedlings. The presence of high HDI predominantly reduced the seedling survival and total biomass of cordgrass, whereas root biomass allocation of cordgrass increased significantly to resist dislodgment and toppling. Moreover, field investigations showed that soil salinity and moisture in the margin of tidal channels were not the limiting factors affecting the establishment of cordgrass seedlings. However, higher propagule pressure combined with suitable soil salinity-moisture conditions (i.e., low salinity and high moisture) laid a firm foundation favoring seedling establishment. Our results highlight the importance of hydrodynamic disturbance as a dominating driver regulating seedling establishment of cordgrass in tidal channel margins and the potential implications for controlling cordgrass landward invasions.

Assessing the Need of Pre-germination Anaerobic Stress-Tolerant Varieties in Indian Soybean (Glycine max (L.) Merrill)

In the wake of unprecedented extreme precipitation scenario, this paper attempts to evaluate the need of breeding efforts to develop soybean ideotypes for moisture extremes in case of excessive rainfall in highly productive soybean areas of India. During the monsoon months, the decadal rainfall analysis in selected high soybean-producing districts of Madhya Pradesh (highest rainfall 350.27 mm in July), Maharashtra (highest rainfall 223.73 mm in July) and Rajasthan (highest rainfall 290.06 mm in August) indicated that the crop has every chance to get exposed to waterlogging stress in its initial stages of germination (pre-germination) and initial seedling establishment, thereby adversely affecting the vegetative phase of the crop. Hence, genetic enhancement of soybean through tolerant varieties/cultivars to pre-germination anaerobic stress should be a viable strategy to overcome waterlogging in any case, providing good yield to soybean producers.

Effects of torrefied wood chip and vermicompost application on vegetation growth and nutrient uptake in the Saemangeum reclaimed land

BackgroundIn reclaimed land, the growth environment for plants may be unfavorable and the initial establishment and growth of seedlings could be limited because of low nutrient and water availability. Fertilization and control of understory vegetation that competes with seedlings may be of help in ameliorating soil physical and chemical properties, resulting in better seedling growth and reclamation success. However, the amount of nutrients understory vegetation absorbs in this ecological process has been rarely studied. Thus, we aimed to investigate the effect of soil amendment on biomass production and nutrient uptake by weeds in the nutrient-poor reclaimed area. We applied three levels of torrefied wood chip (TWC; 0, 2.5, and 5 Mg ha−1) and two levels of vermicompost (VC; 0 and 2.7 Mg ha−1) as soil physical improvements and organic soil amendments in reclaimed land in the Republic of Korea, with Populus euramericana used as the crop tree.ResultsTWC did not influence weed biomass, but 2.7 Mg ha−1 VC significantly increased weed biomass by 21% compared to 0 Mg ha−1 VC treatments. Nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) concentrations in weeds were the highest in control, but there was no statistical difference among treatments. However, VC treatment did marginally increase nutrient uptake in weeds, especially P, K, Ca, and Na. No treatments influenced crop tree height.ConclusionWe conclude that VC can be used as an organic source of nutrients in reclaimed soil and that weed management is necessary to increase treatment effects on crop trees in this salt-affected reclaimed land.

Germination and initial growth of common bean plants under water deficit as affected by seed treatment with S-nitrosoglutathione and calcium chloride

New practices to improve the germination and the initial establishment of seedlings are needed to improve crop development in rainfed areas, where drought events may happen just after sowing. Here, we tested the hypothesis that pre-treatment of common bean seeds with S-nitrosoglutathione (GSNO)—a nitric oxide donor (NO)—or calcium (Ca2+) improves the germination and initial seedling growth under water deficit and both, together, will act synergistically. Firstly, common bean seeds were soaked in GSNO solutions at 50, 100, 500, 1000 and 2000 µM and calcium chloride (CaCl2) at 1, 5 and 10 mM. Then, seeds were subjected to well-watered and water deficit conditions. In another assay, seeds were treated as described above and then the seedlings were transferred to nutrient solution and subjected to water deficit imposed by polyethylene glycol (– 0.3 MPa). In general, our data indicated that pre-treatment of common bean seeds with GSNO or Ca2+ improved germination and root growth under water deficit in a dose-dependent manner. Further tests with a NO scavenger (cPTIO), a Ca2+ chelator (EGTA) and reduced glutathione confirmed the roles of both GSNO and Ca2+ in improving seed germination. However, such improvement in early development of seeds pre-treated with GSNO or Ca2+ was short and no differences among treatments were found at the end of the experimental period. Additionally, seed pre-treatment combining GSNO and Ca2+ aggravated the effects of water deficit on germination and initial development of common bean seedlings, indicating that GSNO nulled any positive effect of Ca2+ and vice versa.

Do polyembryonic seeds of Carapa surinamensis (Meliaceae) have advantages for seedling development?

ABSTRACT Polyembryony is the differentiation and development of multiple embryos in a single seed. This characteristic can provide advantages, as more than one embryo is produced with the same amount of resources, and the probability of establishment of at least one seedling increases. However, sibling seedlings may also increase competition, affecting development and survival. In the present study, the possible advantages and disadvantages of polyembryony were analyzed in the initial establishment of seedlings of Carapa surinamensis (Meliaceae), a tree species that produces monoembryonic or polyembryonic seeds. In this regard, the development of single seedlings was compared with a pair of seedlings emerging from polyembryonic seeds. We compared the development of seedlings attached to or detached from each other and to the seed resources. We observed two levels of competition: (a) for the seed reserves during germination and initial development, as multiple embryos of C. surinamensis share the same reserves, and (b) for external factors, mostly space for root and shoot development, and also for light. Reducing the competition for external factors by separating the siblings was not enough to reduce the effects of competition for seed reserves in the first six months of development. Nevertheless, viable seedlings were produced in all treatments. Thus, depending on sprout management in the nursery, the number of seedlings per seed can be significantly increased by detaching the seedlings, or more vigorous seedlings can be obtained when only one seedling is maintained.

Growth of parica seedlings (Schizolobium amazonicum Huber ex Ducke) cultivated in different organic substrates

The forest plantations depends on appropriate initial seedling establishment, which occurs when primary factors (water, light, CO2 and nutrients) are within appropriate ranges. The purpose this study was to evaluate the growth of young parica plants (Schizolobium amazonicum Huber ex Ducke) grown in different organic substrates (chicken manure, goat manure and organic matter) in proportions of 5, 10, 15 and 20% in yellow argisol. Among the studied treatments, the best response in plant height growth was observed in T2 (5% goat manure in yellow argisol). For the mean diameter, it was observed that T4 (15% goat manure in yellow argisol) allowed greater of growth parica seedlings. In addition, for the quality parameters: ratio of shoot height and root collar diameter (H/RCD), heigh and dry mass air part relation (H/DMAP) and Dickson Quality Index (DQI), the best values were for seedlings cultivated with goat manure, in relation to the other treatments. Therefore, young parica plants grown on substrates with goat and chicken manure showed significant improvements in growth performance, according to fundamentally chemical characteristics of these substrates. Key words: Chicken manure, goat manure, organic matter, seedling production.

Effects of seed hydration memory on initial growth under water deficit of cactus from two populations that occur in different ecosystems in Northeast Brazil

Discontinuity during the rehydration process of seeds that germinate in arid and semi‐arid ecosystems leads to the occurrence of hydration and dehydration cycles (HD cycles). HD cycles play an important role in the persistence and dynamics of plants in these ecosystems. Pilosocereus catingicola subsp. salvadorensis is a cactus that occurs in different ecosystems of northeast Brazil. This species is submitted to different environmental conditions, such as irregularity of soil water availability. This factor directly influences seed production, germination and establishment of new individuals in these ecosystems. The aim of this study was to evaluate the effects of HD cycles on the initial growth of P. catingicola subsp. salvadorensis seedlings from different ecosystems under water‐deficit conditions. Seeds collected in two different ecosystems were submitted to 0, 1, 2 and 3 HD cycles and seedlings from these seeds were submitted to water‐deficit treatments. HD cycles had effects not only during germination, but also in the initial growth and establishment of seedlings. Seeds from different populations had distinct responses to HD cycles and water‐deficit treatments. These effects, as acquisition of a greater tolerance of water deficit, were differentiated between populations of the same species that are established in different ecosystems. The effects of HD cycles interfere directly with seedling recruitment dynamics and the maintenance of these populations.

Efeito da temperatura sobre a germinação e crescimento inicial de sementes de Capsicum frutescens (L.)

A oscilação de temperatura, provocada pelas mudanças climáticas, vem afetando a agricultura em diversos pontos de áreas agricultáveis, com isso, há a necessidade da realização de estudos quanto à adaptabilidade das culturas a uma ampla faixa de temperatura. Desta forma, o objetivo do estudo foi verificar a eficiência da germinação e estabelecimento inicial de plântulas de pimenta malagueta submetidas a temperaturas sub e supra ótimas. O experimento foi conduzido em delineamento experimental inteiramente casualizado, em esquema fatorial constituído por uma espécie e três temperaturas (15 °C, 25 °C e 35 °C). As sementes foram submetidas aos testes de germinação, sob fotoperíodo de 12 horas durante 14 dias, juntamente com primeira contagem de germinação, índice de velocidade de germinação, comprimento de plântulas, massa seca total, condutividade elétrica, atividade respiratória e curva de embebição sob as temperaturas de 15, 25 e 35 °C. A temperatura de 25 °C apresentou superioridade aos demais tratamentos em todas as variáveis testadas. Nas temperaturas de 15 e 35 ºC, a germinação foi completamente inibida. Testes como os executados no presente estudo são eficientes para a determinação da viabilidade das sementes em diferentes faixas de temperatura.

Ação do insecticida tiametoxame aplicado às sementes na emergência e vigor de plântulas de Vigna unguiculata (L.) Walp

The aim of this study was to evaluate the effects of thiamethoxam on the emergence and vigor of cowpea seedlings. The cowpea seeds, cv. ‘Nova era’, were treated with the active ingredient thiamethoxam at dosages of 0.07; 0.14; 0.21; 0.28 e 0.35 g a.i. L‑1. The experimental design used was a randomized block in factorial 2 × 2 × 6, where the first factor were lots of seasons 2013/2014 and 2014/2015, the second factor the two sowing seasons, summer and winter, and the third factor the doses of thiamethoxam. The parameters evaluated were: Percentage emergency, emergency speed index, shoot length and seedling root, and dry weight of shoot and seedling root. There was interaction between the lots and the sowing for the dry mass variable of shoot and root and between doses and the time of planting to emergence and emergence speed index. The insecticide thiamethoxam stimulates the physiological performance of cowpea seeds, occurring positive effects on growth and assimilation of dry matter by the roots, and better initial performance and uniform establishment of seedlings in the winter.