Search Results

You are looking at 1 - 4 of 4 items for :

  • Author or Editor: Warley M. Nascimento x
  • HortScience x
Clear All Modify Search

The growing of transplants in plug cell trays is the primary method of producing brassica transplants in many countries. Seed quality is an important aspect to achieve success in transplant production. Seed size may affect seed performance, seedling growth and development of brassica transplants. Seeds of cauliflower (`Vitoria de vero') and cabbage (`Unio') from Embrapa Vegetables were used in this study. During seed conditioning, seeds were classified using round screens generating three (>1.5, 1.5-2.0, and 2.0-2.5 mm) and four (>1.5, 1.5-2.0, 2.0-2.5, and < 2.5 mm) seed size categories, for cauliflower and cabbage, respectively. The original seed lot was used as control. Seed weight increased with seed size. Seed germination (laboratory) and seedling emergence (greenhouse) were not affected by seed size. In both species, root and shoot weight, and leaf area, measured 30 days after seeding, in greenhouse conditions, increased with seed size. Also, transplants from larger seed size resulted in a significantly higher root weight, shoot weight, and leaf area relative to the original (control) seeds. The results indicate that, overall, an adequate seed conditioning improve brassica transplant quality.

Free access

The effects of seed priming and seed orientation on seedcoat adherence and seedling development of containerized muskmelon transplants were investigated. Seeds of muskmelon `Top Net SR' were primed for 6 days in darkness at 25 °C in an aerated solution of KNO3 (0.35 M). Primed and nonprimed seeds were individually planted in Styrofoam trays in the greenhouse. Seeds were carefully oriented with the radicle down, up, or in the horizontal position, and covered with 0.5 cm of the growing mix. Seed priming and seed orientation affected both seedcoat adherence and seedling development, and interaction between priming and orientation was significant for seedcoat adherence. Our data indicate that seed priming can minimize seedcoat adherence during emergence of muskmelon seeds.

Free access

Temperatures above 30 °C may delay or inhibit germination of most of commercial lettuce cultivars. Ethylene enhances lettuce seed germination at high temperatures. Enzyme-mediated degradation of endosperm cell walls appears to be a crucial factor for lettuce germination at high temperature. The galactomannan polysaccharides in lettuce endosperm cell wall are mobilized by endomannanase. The role of endo-mannanase during germination of lettuce seeds at high temperature (35 °C) and the possible role of etlene in enzyme regulation were investigated. Seeds of thermotolerant (`Everglades'-EVE) and thermosensitive (`Dark Green Boston'-DGB) lettuce genotypes were incubated at 20 and 35 °C in water, 10 mM of 1-aminocyclopropane-1-carboxylic acid (ACC), or 20 mM of silver thiosulphate (STS). Also, seeds were primed in an aerated solution of polyethylene glycol (PEG), or PEG+ACC, or PEG+STS. Untreated seeds germinated 100% at 20 °C. At 35 °C, EVE germinated 100%, whereas DGB germinated only 33%. Seed priming or adding ACC during imbibition increased germination of DGB to 100% at 35 °C. Adding STS during imbibition led to a decrease in germination at 35%C in EVE and completely inhibited germination of DGB. Priming with STS led to reduced germination at 35%C of both genotypes. EVE produced more ethylene than DGB during germination at high temperature. Providing ACC either during priming or during germination led to an increase in endo-mannanase activity, whereas STS inhibited mannanase activity. Higher endo-mannana activity was observed in EVE than DGB seeds. The results suggest that ethylene might overcome the inhibitory effect of high temperature in thermosensitive lettuce seeds via weakening of endosperm due to increased endo-mannanase activity.

Free access

Carrot (Daucus carota L.) seed germination may be erratic or reduced under high temperatures (above 35 °C). Even in tropical genotypes (tolerant to high temperatures during crop development), the negative effects of high temperatures on carrot stand establishment have been observed, especially during summer. The objectives of this study were to characterize commercial carrot cultivars and accession lines for their ability to germinate at high temperature and determine the ethylene production during imbibition at high temperature. Seeds from 34 commercial cultivars and 125 carrot accessions from the North Central Regional Plant Introduction Station were germinated at 25 °C (optimal) and 35 ± 0.5 °C (high) in constant light. Ethylene production during seed imbibition at high temperature was evaluated in some genotypes. Many of the commercial cultivars had reduced germination at 35 °C. ‘XPC-3617’, ‘Alvorada’, ‘Brasilia’, and ‘Esplanada’ had the greatest germination at 35 °C. A greater number of accessions germinated at 35 °C than did the commercial genotypes. The accession PI 319858 germinated 95% at both temperatures and was considered thermotolerant. Six accessions (Ames 7665, Ames 7698, Ames 25031, PI 167082, PI 294637, and PI 319858) germinated above 80% at 35 °C and were also identified as potential sources of thermotolerance. Fifteen other accessions (Ames 7694, Ames 25031, Ames 25036, Ames 25049, Ames 25705, PI 167082, PI 179687, PI 180834, PI 261782, PI 269486, PI 273658, PI 277710, PI 288242, PI 294637, and PI 319858) had thermotolerance ratios of T35/T25 0.85 or greater (where T35 = germination at 35 °C and T25 = germination at 25 °C) and were identified for further testing. The identified thermotolerant genotypes might be useful for carrot seed germination mechanism studies as well as for breeding programs. Ethylene production during seed germination at high temperature was greater in thermotolerant genotypes than in thermosensitive genotypes. High correlations were observed between first germination count at 35 °C and ethylene production, total germination at 35 °C and ethylene production, and thermotolerance ratio and ethylene production.

Free access