Diquat was tested to determine its suitability for use as a preharvest desiccant of selected vegetable seed crops during 1997 and 1998. In separate studies, diquat was applied at 0,0.56, or 1.12 kg·ha-1 ai. to spinach (Spinacia oleracea L.), table beet (Beta vulgaris L.), and coriander (Coriandrum sativum L.) plants at usual swathing time. Except for beet seed in 1998, there was no clear trend toward reduced seed weight with increasing diquat rate. Spinach seed germination in 1998 and coriander seed germination in 1997 were reduced by diquat at 1.12 kg·ha-1 compared to seed from nontreated plants or plants treated with 0.56 kg·ha-1. In all crops, diquat at 0.56 kg·ha-1 was adequate for crop desiccation purposes. However, seed producers should consider the potential benefits from chemical desiccation that may potentially lower germination of the harvested seed. Chemical name used: 6,7-dihydrodipyrido[1,2-α:2′,1′-c]pyrazinediium ion (diquat).
Monica Ozores-Hampton, Thomas A. Bewick, Peter Stoffella, Daniel J. Cantliffe, and Thomas A. Obreza
The influence of compost (derived from MSW and biosolids) maturity on seed germination of several weed species was evaluated. A bioassay was developed by extracting 20 g of compost of different maturities with various volumes of water, then measuring germination percentage of ivyleaf morningglory (Ipomoea hederacea) seeds placed on extract-saturated filter paper in a petri dish. A 20 g (dry weight) compost: 50 mL of water generated an extract that produced the widest percentage seed germination variation in response to composts of different maturity. Ivyleaf morningglory, barnyardgrass (Echinochloa crus-galli L.), purslane (Potulaca oleracea L.), and corn (Zea mays L) were selected as plant indicators to determine the compost maturity stage with maximum germination inhibition. Compost 8-week-old decreased percent germination, root growth, and germination index (combines germination rate and root growth), and increased mean days to germination (MDG) of each plant indicator. Immature 8 week-old compost extract effect on MDG and germination percent of 15 weed species was evaluated. Extract from 8-week-old compost inhibited germination in most weed species, except yellow nutsedge (Cyperus esculentus). Compost extracts derided from immature (3-day, 4-, and 8-week-old) compost resulted in delayed and reduced germination percent of important economic weed species.
Rachel Emrick, D. L. Creech, and G. Bickerstaff
This project tested rates of lignite-activated water (LAW) for its influence on seed germination, cutting propagation, and plant performance. LAW is a product of CAW Industries, Rapid City, S.D. LAW is water-activated by lignite in a process that includes the addition of sulfated castor oil, calcium chloride, magnesium sulfate, sodium meta silicate, and fossilized organics from refined lignite. LAW is reported to improve many plant performance traits. Four rates were used in this study. Seed germination trials indicated no significant differences in germination percentage with LAW applications with the two species tested, Echinacea purpurea and Hibiscus dasycalyx. In a “closed” system, LAW enhanced cutting propagation success of Aster caroliniana, Cuphea micropetala, and Verbena `Homestead Purple', as measured by percent rooting and dry weight of roots produced. Cutting propagation of two woody species, Illicium henryi and Rosa banksiae, was not improved with LAW additions. In the SFASU Arboretum, pansy performance, as measured by plant dry weight, was improved one month after establishment.
Lewis W. Jett, Gregory E. Welbaum, and Ronald D. Morse
Priming, a controlled-hydration treatment followed by redrying, improves the germination and emergence of seeds from many species. We compared osmotic and matric priming to determine which was the most effective treatment for improving broccoli seed germination and to gain a greater understanding of how seed vigor is enhanced by priming. Broccoli (Brassica oleracea L. var. italica) seeds were osmotically primed in polyethylene glycol (PEG 8000) at -1.1 MPa or matrically primed in a ratio of 1.0 g seed:0.8 g synthetic calcium silicate (Micro-Cel E):1.8 ml water at -1.2 MPa. In the laboratory, germination rates and root lengths were recorded from 5 to 42C and 10 to 35C, respectively. Broccoli seeds germinated poorly at >35C. Root growth after germination was more sensitive to temperatures >30C and <15C than radicle emergence. Matric and osmotic priming increased germination rate in the laboratory, greenhouse, and field. However, matric priming had a greater effect on germination and root growth rates from 15 to 30C. Neither priming treatment affected minimum or maximum germination or root growth temperatures. Both priming treatments decreased the mean thermal time for germination by >35%. The greater germination performance of matrically primed seeds was most likely the result of increased oxygen availability during priming, increased seed Ca content, or improved membrane integrity.
Kai Zhou, Weiming Guo, and Zhongchun Jiang*
The autointoxication of chrysanthemum was studied using water extract of Dendranthema morifolium's rhizospheric soil. Results of bioassays showed that the water extract inhibited chrysanthemum seed germination and the activities of some important root enzymes. The seedling nitrate reductase activity was decreased linearly with increasing concentration of the extract. The activity of root dehydrogenase was inhibited only at the highest concentration tested [3.2 g·mL-1, dry weight (DW)], but was stimulated at a lower concentration tested (1.6 g·mL-1, DW). Malondialdehyde content increased at higher than 1.6 g·mL-1, DW concentrations of the extract. The autointoxication phenomenon might be related to the difficulties in continuous plantings of chrysanthemum at the same location.
William J. Carpenter
Soaking palm seed in water for 1 to 21 days prior to planting reduces the number of days required for germination (3). Loomis (1) found soaking seeds of Acrocomia scierocarpa and Astrocaryum mexicanum palms for 2 to 3 weeks following hot water scarification at 100°C for 3 min hastened seed germination. Rees (3) reported soaking Copernicia cerifera (Mart.) seeds in water for 7 days at 38° to 42° also accelerated germination after planting. Presoaking Alexandra palm [Archontophoenix alexandrite (F.J. Muell.) H. Wendl & Drude] seed in water for 24 to 72 hr at 25° was reported by Nagao and Sakai (2) to stimulate germination. The purpose of this study was to determine the effect of temperature during a 7-day preplanting period on imbibed and nonimbibed seed and to compare seed soaking in water with moist peatmoss on germination percentages and numbers of days required to achieve 50% final germination.
James E. Henrich, Dennis P. Stimart, and Peter D. Ascher
Seeds of 29 terrestrial orchid species representing 15 genera were surface sterilized by immersion in 0.5% sodium hypochlorite containing a wetting agent, washed, sown on a completely defined, semisolid embryo culture medium containing macro- and microelements, sucrose, amino acids, and vitamins, and incubated in the dark at 25°C. Six months after sowing, 16 species from 9 genera germinated and continued development while 13 species from 10 genera failed to germinate. Species of Cypripedium, Goodyera, Platanthera and Spiranthes differed in response in that one or more of each germinated and one or more did not. Seedling development was similar for most germinating species and progressed to the formation of a shoot or shoot initial in all but one. Apparently the mycorrhizal association thought to be required for terrestrial orchid seed germination and early seedling development can be replaced with aseptic culture on a completely defined medium for many terrestrial orchids.
J. Brent Loy and Kathleen B. Evensen
Continuous, low intensity, far red (FR) irradiation prevented germination, and continuous, low intensity, red (R) irradiation decreased the rate of germination of seed of dw-2 dwarf watermelon [Citrullus lanatus (Thunb.) Matsumara and Nakai]. Intermittent, 15 minute light treatments with R or FR at 6 hour intervals affected germination similarly to continuous irradiations. Seeds germinated best in darkness and would germinate in darkness following prolonged incubation in FR light. A short exposure to R light following a prolonged FR treatment enhanced subsequent germination in darkness (D), and the effect of R light was reversed by a short exposure to FR light, indicating phytochrome control of germination. Responses to single, short exposures to FR light after different periods of incubation, and to different intervals of D and prolonged FR light, indicated that germination of dwarf watermelon seeds is regulated by phytochrome between about 6 to 24 hours of incubation at 29 to 30°C.
Warley M. Nascimento, Daniel J. Cantliffe, and Donald J. Huber
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.
Gregory L. Reighard, David Ouellette, Kathy Brock, and William Newall Jr.
Poor peach seed germination can be a problem for commercial tree fruit nurseries. Even standard rootstocks such as Lovell and Nemaguard do not always have high germination rates. New seed-propagated rootstocks under development, such as Guardian peach rootstock, often are selected for their field traits, with nursery characteristics being of secondary importance. Guardian rootstock is derived from bulked open-pollinated seed from a number of F1 seedling selections. Germination of Guardian bulked seed has been poor. Four pre-stratification cold treatments were given to four 100-seed lots each of Lovell, Nemaguard, and 10 Guardian selections prior to planting each year (1994 to 1998) in a Cecil sandy loam at Musser Fruit Research Center near Clemson, S.C. Treatments included taking dry, refrigerated seed that were harvested in August and soaking 100-seed seedlots in 1500 mL perlite and 400 mL distilled water for 0 (no soaking), 2, 4, 6, and 8 weeks at 6 °C before sowing (typically early November). All treatments consisted of 25 seeds per replicate (4 reps/year) per rootstock or selection and were sowed the same day. The experiment was analyzed as a blocked split plot design with duration of stratification the whole-plot and seedlot the sub-plot. Number of emerged seedlings were counted weekly starting in January of each year. There were significant differences between stratification treatments, seedlots and years. The 6-week pre-stratification had the highest germination over 5 years and like the 8-week treatment advanced the average germination date by 20 to 30 days. Nemaguard (65%), Lovell (64%), and Guardian 3-17-7 (60%) had the best germination percent across all treatments and years, with SL2891 (42%) slightly less. All other selections averaged less than 25%. Year-to-year variation was large, indicating strong environmental influences on seed germination despite the pre-stratification treatments.