Uso de substâncias reguladoras e não-específicas na germinação de sementes de licuri (Syagrus coronata (Mart.) Becc.)

The slow and irregular germination pattern of palm tree seeds justifies the use of mechanisms to speed up the germination process. This article looks at the germination effects of licuri seeds (Syagrus coronata (Mart.) Becc) when they were imbibed in water, as well as in a solution containing gibberellic acid, and another containing thiourea. The water imbibition had a great effect on the germination and germination speed of endocarp seeds. For seeds without endocarp, however, treatment caused tissue deterioration, reducing germination rate. High levels of gibberellic acid solutions increased germination rate of seeds submitted to 12-48 hours of imbibition, resulting in 65% and 52% respectively. Thiourea promoted the highest germination and germination speed during the 12 hour treatment period. Data suggest that the presence of endocarp on licuri seeds influences the germinative process. The exposure of seeds to water and thiourea solutions for 12 hours was the most recommended treatment to promote the germination of seeds.A germinação de sementes de palmeiras é bastante lenta e desuniforme, tornando-se necessário adotar mecanismos que acelerem este processo. Este trabalho examina o efeito da embebição em água, do ácido giberélico e da tiouréia na germinação de sementes de licuri (Syagrus coronata (Mart.) Becc.). A embebição em água influenciou significativamente a germinação e o Índice de Velocidade de Germinação (IVG) das sementes com endocarpo; nas sementes sem endocarpo a exposição à água promoveu deterioração dos tecidos, reduzindo a taxa de germinação. Soluções de ácido giberélico em concentrações elevadas foram eficientes no aumento da porcentagem de germinação das sementes alcançando 65% e 52%, respectivamente, quando submetidas a 12 e 48 horas de embebição. Em relação ao uso da tiouréia, as maiores taxas de germinação e IVG foram obtidas quando as sementes foram embebidas por 12 horas. Os dados sugerem que a presença do endocarpo em sementes de licuri influencia no processo germinativo e que a embebição parece ser um fator importante para desencadear esse processo. A exposição das sementes com endocarpo em água e soluções de tiouréia durante 12 horas foram os tratamentos mais indicados em promover a germinação das sementes

Influência do armazenamento nos teores de açúcares solúveis totais e redutores em sementes de Syagrus coronata (Martius) Beccari (Arecaceae)

In the semi-arid Northeast of Brazil Syagrus coronata has great nutritional, ornamental and foraging potential. Despite its great utility this species has been subject to excecsive exploitation, which has severely reduced natural populations. The objectives of this work were to evaluate the influence of storage on total and reducing soluble sugars content in seeds of S. coronata and for the establishment of efficient conservation protocols. The experimental design was completely randomized, in a factorial scheme 4x4+1, being four storage periods, four storage conditions, and the control. The results expressed significant difference for the evaluated parameters. The contents of total and reducing soluble sugars showed oscillations among the storage periods. However, the trend was an increase of these sugars with storage time for all the storage conditions, except in the humid room. These results indicate that sugar degradation by metabolism was affected by external conditions.No semi-árido Nordestino, Syagrus coronata tem grande potencial alimentício, ornamental e forrageiro. Apesar de sua grande utilidade, essa espécie tem sido alvo de super exploração, o que tem acarretado a rápida diminuição de populações naturais. Este trabalho teve como objetivo avaliar a influência da estocagem nos teores de açúcares solúveis totais e redutores em sementes de S. coronata, servindo de base para o estabelecimento de protocolos eficientes de conservação. O delineamento experimental foi inteiramente casualizado, em arrranjo fatorial 4x4+1, sendo quatro períodos de armazenamento, quatro condições de estocagem e testemunha. Os resultados expressaram diferença significativa para os parâmetros avaliados. Os teores de açúcares solúveis totais e redutores apresentaram oscilações entre os períodos de armazenamento. No entanto, a tendência foi de aumento desses açúcares com o tempo de armazenamento para todos os ambientes, exceto ambiente úmido. Esses resultados mostram que o metabolismo de degradação dos açúcares foi afetado por condições externas

Effect of osmopriming on germination and initial growth of physalis angulata L. under salt stress and on expression of associated genes

This study aimed to evaluate the effects of priming on seed germination under salt stress and gene expression in seeds and seedlings of P. angulata L. After priming for 10 days, seed germination was tested in plastic trays containing 15 ml of water (0 dS m-1 - control) or 15 ml of NaCl solution (2, 4, 6, 8, 10, 12, 14 and 16 dS m-1). Fresh and dry weight of shoots and roots of seedlings were evaluated at 0, 2, 4, 6, 8 dS m-1. Total RNA was extracted from whole seeds and seedlings followed by RT-qPCR. The target genes selected for this study were: ascorbate peroxidase (APX), glutathione-S-transferase (GST), thioredoxin (TXN), high affinity potassium transporter protein 1 (HAK1) and salt overly sensitive 1 (SOS1). At an electroconductivity of 14 dS m-1 the primed seeds still germinated to 72%, in contrast with the non-primed seeds which did not germinate. The relative expression of APX was higher in primed seeds and this may have contributed to the maintenance of high germination in primed seeds at high salt concentrations. GST and TXN displayed increased transcript levels in shoots and roots of seedlings from primed seeds. Priming improved seed germination as well as salt tolerance and this is correlated with increased expression of APX in seeds and SOS1, GST and TXN in seedlings.</p

Rainfall, not soil temperature, will limit the seed germination of dry forest species with climate change

Drylands are predicted to become more arid and saline due to increasing global temperature and drought. Although species from the Caatinga, a Brazilian tropical dry forest, are tolerant to these conditions, the capacity for germination to withstand extreme soil temperature and water deficit associated with climate change remains to be quantified. We aimed to evaluate how germination will be affected under future climate change scenarios of limited water and increased temperature. Seeds of three species were germinated at different temperatures and osmotic potentials. Thermal time and hydrotime model parameters were established and thresholds for germination calculated. Germination performance in 2055 was predicted, by combining temperature and osmotic/salt stress thresholds, considering soil temperature and moisture following rainfall events. The most pessimistic climate scenario predicts an increase of 3.9 °C in soil temperature and 30% decrease in rainfall. Under this scenario, soil temperature is never lower than the minimum and seldomly higher than maximum temperature thresholds for germination. As long as the soil moisture (0.139 cm3 cm3) requirements are met, germination can be achieved in 1 day. According to the base water potential and soil characteristics, the minimum weekly rainfall for germination is estimated to be 17.5 mm. Currently, the required minimum rainfall occurs in 14 weeks of the year but will be reduced to 4 weeks by 2055. This may not be sufficient for seedling recruitment of some species in the natural environment. Thus, in future climate scenarios, rainfall rather than temperature will be extremely limiting for seed germination

The negative effect of a vertically-transmitted fungal endophyte on seed longevity is stronger than that of ozone transgenerational effect

Seed morphology underpins many critical biological and ecological processes, such as seed dormancy and germination, dispersal, and persistence. It is also a valuable taxonomic trait that can provide information about plant evolution and adaptations to different ecological niches. This study characterised and compared various seed morphological traits, i.e., seed and pod shape, seed colour and size, embryo size, and air volume for six orchid species; and explored whether taxonomy, biogeographical origin, or growth habit are important determinants of seed morphology. We investigated this on two tropical epiphytic orchid species from Indonesia (Dendrobium strebloceras and D. lineale), and four temperate species from New Zealand, terrestrial Gastrodia cunnninghamii, Pterostylis banksii and Thelymitra nervosa, and epiphytic D. cunninghamii. Our results show some similarities among related species in their pod shape and colour, and seed colouration. All the species studied have scobiform or fusiform seeds and prolate-spheroid embryos. Specifically, D. strebloceras, G. cunninghamii, and P. banksii have an elongated seed shape, while T. nervosa has truncated seeds. Interestingly, we observed high variability in the micro-morphological seed characteristics of these orchid species, unrelated to their taxonomy, biogeographical origin, or growth habit, suggesting different ecological adaptations possibly reflecting their modes of dispersal

Respostas morfofisiológicas in vitro de plântulas de Anadenanthera colubrina (Vell.) Brenan var. cebil (Griseb) Altschul In vitro morphophysiological answers of the seedlings of Anadenanthera colubrina (Vell.) Brenan var. cebil (Griseb) Altschul

Este trabalho teve como objetivo avaliar o estabelecimento in vitro de Anadenanthera colubrina var. cebil, através das respostas morfofisiológicas das plântulas submetidas a várias condições de cultivo. As sementes foram desinfestadas e inoculadas em placas de Petri contendo papel germtest previamente esterilizado e umedecido com água estéril. As placas ficaram no escuro por dois dias até que ocorresse a germinação das sementes e, em seguida, transferidas para tubo de ensaio contendo meio de cultura WPM. Foram avaliados três tipos de fechamentos dos tubos de ensaio: filme de PVC, tampa plástica sem filme de PVC e tampão de algodão. No segundo experimento, o meio de cultura foi suplementado com carvão ativado (0,0; e 82,2 mM) e diferentes concentrações de sacarose (0,0; 29,21; 58,43; e 87,64 mM). Ao final de 30 dias, observaram-se efeitos altamente significativos dos tipos de fechamento sobre todas as variáveis analisadas: comprimento da parte aérea (CPA), número de folhas (NF), número de pinas (NP), matéria seca da parte aérea (MSPA), abscisão foliar (AF), comprimento da raiz (CR), matéria seca da raiz (MSR) e número de raízes secundárias (NRS). A AF foi reduzida em 7,3 vezes, quando os tubos de ensaio foram fechados com tampão de algodão em relação ao fechamento com filme de PVC. Os maiores valores de CPA (102,5 mm), NF (3,0), CR (194,7 mm) e NRS (47,88) foram obtidos com 29,21 mM de sacarose; a MSPA (59,1 mg), quando utilizou 58,43 mM e MSR (33,37 mg), com 87,64 mM de sacarose. O carvão ativado apresentou efeito significativo apenas em NRS, com maior valor (45,79) na presença desse composto.<br>This work aimed to evaluate the in vitro establishment of the species Anadenanthera colubrina var. cebil, throug the morphophysiological answers of the seedlings subjected to several culture conditions. The seeds were desinfested and inoculated in Petri plates containing germtest paper, previously sterilized and imbibed with sterile water. The plates were kept in the dark for two days, until the seeds germinated. Then, they were transferred to the test tube containing WPM medium. Three types of test tube closings were evaluated - PVC film, plastic lid without PVC film and cotton lid. In the second experiment, the culture medium was supplied with activated charcoal (0,0 and 82,2mM) and different sucrose concentrations (0,0; 29,21; 58,43; 87,64mM). After 30 days, highly significant effects of the types of closure were observed on all the variables analysed - aereal part length (APL), number of leaves (NL), number of pinnas (NP), dry matter of aereal part (DMAP), leaf abscission (LA), root length (RL), root dry matter (RDM) and number of secondary roots (NSR). The LA was reduced in 7,3 times when the cotton lid was used instead of the PVC film. The greatest values for APL (102,5 mm), NP (3,0), RL (194,7 mm) and NRS (47,88) were obtained with 29,21mM of sucrose. For DMAP (59,1 mg), when it used 58,43mM, and for RDM (33,37 mg), with 87,64mM of sucrose. The activated charcoal showed significant effects only for the variable SRN, presenting the greatest value (45,79) in the presence of this compound