Table beet (Beta vulgaris L.) seeds are characteristically slow germinating, and have a large time spread of germination. These characteristics interfere with the early establishment of a uniform, vigorous stand of seedlings in cold wet soil. This study was undertaken to determine if osmoconditioning (OC) of table beet seeds in polyethylene glycol 6000 (PEG) and MgSO4 solutions and/or other measures would improve germination and/or reduce germination time and thereby improve emergence, seedling establishment and yield. Seed balls of ‘Ruby Queen’ and ‘Cardenal’ were osmoconditioned in −1.2 and −1.18 MPa solutions of PEG and MgSO4, respectively. Treatments were performed at 15 °C for 7 days in the light. The benefits of OC were not lost by drying back the seeds. Aeration during OC followed by a 2 min rinse with water was the most effective treatment in improving germination or emergence in laboratory and growth chamber studies. In the 1980 field trial, OC in PEG improved the rate of emergence by 2 to 3 days, the stand by 40% and the root, top, and total yield by 40, 66, and 59%, respectively. In 1982, seedling emergence was biphasic. The first phase lasted 23 days and showed large differences in rate of emergence and stand between osmotically treated and untreated seeds and resembled the 1980 emergence pattern. The second phase commenced after a 30 mm rain with a resurgence of emergence in all treatments. The resurgence rate was highest in untreated seeds and this reduced the treatment differences in stand and yield. The resurgence was attributed to invigoration of the non‐germinated seed by low soil water potential (drought). Several MgSO4‐OC treatments increased the number of roots but decreased root size.

The apical 1-cm hypocotyl of dark-grown 'Clark' soybean ( Glycine max IL.l Meff.) seedlings produced ethylene at rates of 7 to 11 nanoliters per hour per gram when attached to the cotyledons. Such physiologically active rates occurred prior to the deceleration of hypocotyl elongation caused by the temperature of 25 C.Daiy exposure of the etklated s to red iht promoted hypocotyl elongatin and prevented Its lateral swelling. Red liht treatment also caused a 45% decrease In ethylene production. Far red Iradiatin following the red treatment reversed the red effects, suggesting that the ethylene intervenes as a regulator in the phytochrome control of 'Clark' soybean hypocotyl growth at 25 C.It has been shown (5, 10) that hypocotyl elongation of certain soybean cultivars, e.g. "Clark,' is inhibited and the hypocotyl swells when grown at 25 C in darkness. At 20 and 30 C, the hypocotyl grows normally as other cultivars do, e.g. 'Mandarin,' at all three temperatures. We have previously presented (10) evidence to support the hypothesis that enhanced endogenous ethylene production at 25 C is responsible for both the inhibition and the swelling. germination paper (6 x 14 cm) with the embryos upward. Sheets were rolled into a cylinder, which was stood in 50 ml of distilled H20 in a l,000-ml glass jar. Seedlings were grown in darkness at 25 C. Ali of the manipulations were conducted under a dim green light, consisting of a 25-w incandescent lamp filtered through two layers of green Cinemoid and one layer of blue cellophane. The data for the hypocotyl length measurements were taken from our previous report (10). Prior to every experiment ungerminated seeds, seeds with broken cotyledons, seed coats, and inverted seedlings were discarded. Ethylene Determination. In measuring endogenous ethylene evolution of the seedlings, five or six seedlings, still wrapped in paper, were transferred to a 210-ml glass cylinder (3.4 i.d. and 23 cm long) and sealed. Each treatment consisted of three glass cylinders. After closure for 5 hr, 1-ml samples were withdrawn with a Hamilton gas-tight syringe. Ethylene was measured in a Varian 2400 gas chromatograph equipped with a hydrogen flame ionization detector and a stainless column (213 x 0.32 cm) packed with activated alumina.Localzation of Ethylene Production. Immediately after each 5-day-old seedling was cut into specific segments (Fig. 1) they were allowed to float in 1% sucrose -50 mm KH2PO4 solution for I to 4 hr (experiment I) and 9 to 12 hr (experiment II) prior to being transferred to appropriate containers and sealed for ethylene measurements. Excised portions of the seedlings were transferred to 39-ml flasks (except for the roots which were placed in 57-ml centrifuge tubes containing a filter paper soaked with the sucrosephosphate solution) and sealed. After closure for 5 hr, I-ml samples were withdrawn for gas analysis.Light Experments. The red light source consisted of two 20-w, Toshiba white fluorescent bulbs filtered through one layer of 3-mm red Plexiglas and two layers of r...

Curly dock (Rumex crispus L.) seeds failed to germinate in the dark, but germinated readily in light at 15, 20, and 25C. A secondary dormancy was induced in these seeds by 6 days of dark or light incubation at 30C (thermodormancy), by 6 days of dark incubation at 15C, or by a prolonged soaking in −15.7 bar polyethylene glycol-6000 (PEG) solution at 15C in light. The secondary dormancy induced at 15C was partially removed by 2-chloroethylphosphonic acid (ethephon) in presence of light; however, when the dormancy was induced at 30C, an addition of gibberellin A4+7 (GA4+7) to ethephon was necessary for effective removal of the dormancy. The ability of growth regulators to remove the secondary dormancy induced by prolonged dark incubation at 15C decreased progressively in light as the duration of dark incubation increased. The water-potential studies indicate that the thermodormancy can be attributed, at least in part, to the inability of the embryonic cells to lower their water potential to a level sufficient to cause radicle protrusion.

In genetically-heterogeneous outcrossing species, there is the opportunity for selection based on the male gamete . Buckwheat (Fagopyrum esculentum Moench) is self-incompatible with one ovule per flower, so pollen competition at each ovule can be studied . The occurrence of selection among pollen parents was determined, as well as the relative importance of prezygotic and post-zygotic selection . Mixed pollinations from two donors produced nonrandom paternity, with one of the donors being favored about 2 :1 on several females . Individual plants showed significant variation in the speed of pollen-tube growth . Therefore, prezygotic selection is likely to have occurred based on the speed of pollen tube growth . In single-donor pollinations, donors had equal success as expected in the absence of post-zygotic selection among donors . However, a significant male x female interaction was found, consistent with postzygotic selection against particular parental combinations . To test whether male fitness is reduced by increased allocation to seed filling during pollen production, large-and small-seeded lines were compared, both as pollen donor and as pollen recipient . The large-seeded line was better in both roles, thus there was no evidence that greater allocation to seeds reduced the quality of the pollen .

Tartary buckwheat (Fagopyrum tataricum) was successfully hybridized with common buckwheat (F esculentum), both diploid (2n = 16), using the latter as male parent during bud pollination . The barrier normally encountered in such hybridization was overcome by enhancing the cross-compatibility of the two species, which was accomplished by synthesizing a unique genotype of common buckwheat . This novel plant was produced by selecting common buckwheat plants that exhibited, at isozyme loci PGM, SKDH and ADH, alleles with similar mobility to those found in tartary and then transferring these alleles to a single plant through six generations of breeding . Ovule culture was used to rescue the 7-10 day old embryos . On the rescue-culture medium 41% of the hybrid embryos formed calli larger than 200 pm in diameter. Most ceased to grow before reaching 1500 µm, but four out of 263 cultured ovules continued to grow as callus . One of these differentiated and formed callus with buds and shoots from which cloned plants were produced . The remaining embryos either did not grow at all or formed very small calli . When tartary was crossed with the original genotype of common buckwheat, only 22% of the hybrid embryos formed small calli and none differentiated . Hybridity of the calli and the plantlets was determined by RAPD and isozyme analysis, respectively . Flowers produced by the hybrid plants were of the same type (homomorphic) and size as those of tartary, but with white sepals like common buckwheat .