Abstract
Potential benefits of priming seeds were first indicated by Levitt and Hamm in 1943 (14), reported for vegetable seed in 1963 by Ells (7), and summarized in 1975 by Hey-decker et al. (11). Effective priming causes the treated seed to germinate earlier and with greater uniformity than untreated seed (11). To date, the technique of priming seeds has been used to solve problems concerning thermodormancy (9), cold soil temperatures (15), and to increase the rate and uniformity of crop emergence (7, 10, 11). However, the methodology of priming, especially for PEG solutions, has not been readily adaptable to handling the large amounts of seed that would be required for commercial use (4, 10). Although the successful use of the SPS to ‘bulk’ prime carrot (12) and pepper (3) seeds has been reported, the design of the SPS and the methodology of its use have not been adequately described. Therefore, this report describes the SPS and the methodology that makes it functional.
The optimum conditions for priming pansy (Viola × wittrockiana) seeds were in aerated osmotic solutions of polyethylene glycol 8000 (PEG 8000) at – 1.0 MPa for 7 days at 15C. Priming at – 0.8 MPa and 15C caused 8% to 26% of seeds to germinate during 4 to 13 days of priming. Increasing numbers of abnormal seedlings developed when priming was extended beyond 7 days. Final germination percentages were better in laboratory studies at 35C for primed (51%) than nonprimed (10%) seeds. Removal of the mucilage released by the seed with 240 g KOH or 170 g NaOH/liter for 15 or 30 seconds during priming did not affect total germination percentages, but did improve seed handling. Primed seed had higher, faster, and more uniform germination than nonprimed seeds after sowing in growing medium in plant growth chambers or greenhouses.
Seeds of `Ace 55VF' tomato were soaked in solutions of -1.0 MPa Instant Oceanâ„¢ (inorganic salt mixture) or -0.6 MPa polyethylene glycol 8000 (P.E.G.) at 25 C for 1 week. `Mary Washington' asparagus seeds were soaked in the same solutions for 2 weeks. In solutions of decreasing matric or osmotic potentials, primed seeds germinated faster than untreated seeds. Germination percentages of primed seeds generally were greater than those of untreated seeds when water stress exceeded -0.5 MPa. All primed seeds, whether dried to a low moisture content or not, germinated faster than untreated seeds after storage for up to 3 months at 4 C or 20 C. Primed asparagus seeds germinated most rapidly and synchronously after storage at 4 C and high moisture content. Storage temperature and seed moisture content had no effect on subsequent germination of primed tomato seeds.
Verbena seed when harvested, has a natural dormancy that gradually dissipates during a 5 to 8 month period of dry storage. In this study, the gradual loss of the dormancy causing factor was correlated with germination percentage. Acetone treatment of verbena seeds was found to cause a slight, but non-significant, reduction in total germination. However, the infusion of gibberellic acid (GA4/7) and kinetin (KIN) with the acetone at various concentrations improved germination. The traditional method of seed osmoconditioning using Polyethylene Glycol (PEG 8000) at -1.0 MPa caused a non-significant reduction in percent germination, similar to that with acetone. When growth regulators were mixed with the osmoconditioning solution, at the concentrations used with acetone, a definite and significant improvement in terms of rate and percent of germination was observed.
Abstract
The effect of polyethylene glycol (PEG)-induced water stress on stomatal and nonstomatal inhibition of photosynthesis of apple seedlings (Malus domestica Borkh.) grown in solution culture was investigated. Water stress was applied gradually by modifying the nutrient solution water potential daily to a minimum of -8.0 bar. Nutrient solution of less than or equal to water potentials -6 bar decreased net and gross photosynthesis rates. Stomatal and nonstomatal factors were responsible for photosynthetic inhibition. Nonstomatal inhibition of photosynthesis appears to be due to decreased capacity for CO2 fixation and not increased photorespiration. The ratio of gross to net photosynthesis was not affected. A higher level of water stress was required to affect mesophyll resistance than stomatal resistance and/or there was a lag time for mesophyll resistance to respond to stress.
Abstract
Relationships were examined among water deficits, ABA content of leaf tissue, and leaf abscission in intact Ficus benjamina L. (weeping fig). Water deficits were imposed by withholding water from plants growing in sand and by raising the osmotic potential of water culture solutions through the addition of PEG 6000. Unconjugated ABA was quantitatively analyzed using gas chromatography. A strong inverse linear correlation existed between ABA content of leaves and plant water potential. No relationships between ABA content and leaf abscission were observed. ABA content in leaves collected from plants growing in a greenhouse, having a plant water potential of −0.5 bar, was about 75 fold greater than the ABA content of leaves collected from plants maintained in a controlled environment room, having plant water potentials of −8.0 bar. Results indicate that ABA does not independently regulate leaf abscission in Ficus benjamina.
Hardiness Zone ratings. Each of the five ingredients in our spray was chosen for its specific mode of action in hypothetically improving resistance to cold in plant tissues. In animals and insects, polyols like polyethylene glycol (PEG) appear to enhance
The effect of preplant conditioning on germination of three flower seeds, Bupleurum griffithii (Tourn.) L. (thorough-wax), Ammi majus L. (greater ammi), and Cirsium japonicum DC. Per. (Japanese thistle), were studied. Seeds were osmoconditioned with -1.2 MPa polyethylene glycol 8000 (PEG) solution and matriconditioned with moist Micro-Cel E (ratio of 2 seed: 0.6 carrier: 3 water by weight for Bupleurum and Cirsium; for Ammi the ratio was 2:1.4:6) and moist expanded vermiculite #5 (the ratio was of 2 seed: 0.6 carrier: 2 water for Bupleurum). In some treatments, water in the matriconditioning mixture was replaced with 1 mm gibberellin A4+7 (GA) or 0.2 % KNO3. In Bupleurum, matriconditioning with Micro-Cel E was generally superior to matriconditioning with vermiculite or osmoconditioning with PEG. A 4-day matriconditioning with Micro-Cel E and germination in the dark reduced the period required for 50% (T50 of final germination by 4 days and improved the percentage germination at 20C (73 % vs. 95%), compared to nonconditioned seeds germinated in the dark. The treatment also improved the percentage of germination at 15C (68% vs. 95%) and effectively removed the thermoinhibition of germination at 25 and 30C. Germination was inhibited to a greater extent for seeds kept in the light during matriconditioning and germination than for seeds conditioned in darkness and germinated in light or conditioned in light and germinated in darkness. Nitrate added during conditioning in light prevented inhibition of germination, provided seeds were kept in darkness during germination. In A. majus, germination in light after 4-day matriconditioning reduced the T50 by ≈2 days, but had little effect on percentage germination. Both GA and irradiance equally promoted germination when added during osmoconditioning, with nitrate having no effect. In C. japonicum, a 4-day matriconditioning or a 7-day osmoconditioning reduced the T50 of germination by -2 days and improved the percentage germination to some extent. Neither irradiance nor nitrate had any significant effect.
germination in P. trifoliata , the need for a more precise procedure exists, and there is no information about the germination of seeds of P. crenulata . Soaking seeds in water with dissolved polyethylene glycol (PEG), called osmopriming, has been used to
As ancestors of higher plants, mosses offer advantages as simple model organisms in studying complex processes. The moss Physcomitrella patens became a powerful model system in the last few years (Cove and Knight, 1993). Adaptation of PEG-mediated DNA uptake procedure has permitted the establishment of efficient molecular genetic approaches. To study possible effects of a Type I phytochrome, the potato phyA gene was introduced into the moss P. patens. Stabile transformants exhibited a range of similar phenotypes (Schaefer et al., 1991). The aim was to differentiate the wild type from the transgenic moss plants with simple, quick measurements providing data suitable for analyzing offspring populations. Ten different morphological and biochemical methods were used to investigate the phenotype in order to choose the best phenotypical category to indicate the presence and the effect of the phytochrome transgene. Two selected strains were used with the most and the least intensive phenotypical features (3*, 29), along with their selfed progenies, as well as progenies from crosses with the nicotinic-acid auxotrophic mutant. The best methods to differentiate between wild type and transgenic plants were the statistical analysis of the number of gametophores, photometric measurement of pigment contents and composition under different light conditions, color evaluation by PC-based vision system, and visual observation of morphogenetic changes. Our investigations support that the potato phytochrome transgene has a pleiotropic effect in the moss P patens. The methods used would be applicable for the characterization of mosses with different transgenes.