Abstract
Transverse cracking of cotyledons, (TVC), varied from 0 to 95% among bean cultivars and was enhanced by planting dry seed in wet soils. A more reliable indication of TVC potential was obtained if the seed was placed in small beakers and covered with water. Covering the hilum with grease slowed imbibition and reduced TVC in tolerant lines. Soaking for 45 minutes in ethanol prior to imbibition in water accelerated imbibition and increased TVC. Seed coat removal prior to imbibition further enhanced imbibition and increased TVC. None of these 3 treatments changed the relative amount of TVC, but seed coat nicking or removal prior to imbibition gave the most reliable test.
Potassium and Mg in cotyledons were negatively correlated with cultivar susceptibility. Calcium was sometimes significantly correlated with TVC in seed grown in a given location, but the correlations could be lacking or of opposite sign in seed grown elsewhere.
Abstract
We investigated the areas of water penetration and the anatomical structures of hilar regions of permeable and impermeable seed coats of lima beans (Phaseolus lunatus L.). Results indicate that water can enter permeable seeds through the hilum, raphe, and micropyle. In impermeable seeds water cannot pass through any of these areas. Anatomical data confirm that there were no structural differences in the testae of permeable and impermeable seeds, but a noticeable difference was apparent in the hilar region. In permeable seeds the palisade layer did not connect evenly in the hilar canal. By contrast, the hilar canals of impermeable seeds had connected palisade layers that were uniformly coated with a cuticular layer. Micropylar openings were clearly visible in permeable seeds, but these openings were occluded and well covered with cuticle in impermeable seeds. Visible differences were evident in the raphe.
The white-seeded snap bean `Early Wax' (Phaseolus vulgaris L.) was crossed with a black-seeded breeding line 5-593. The F2 segregation data are consistent with a three-gene model, in which all three genes must be homozygous recessive to give white seed coat. One of the genes is t because of segregation in F2 for plants with white flowers and partial seed coat coloration. We hypothesize that the genes ers and ers2 in the presence of f block all seed color expression in all genes for partial coloration of seed. The hypothesis of three recessive genes was confirmed in a backcross test involving `Early Wax' x F1. The interaction of ers and ers2 was tested in progeny tests of partly colored BC-F1 plants. One of the erasure genes, ers2, blocks color expression in color zones close to the hilum, but only in the presence of ers. The other erasure gene, ers, blocks color expression only in color zones beyond those close to the hilum in a manner similar to the restr locus of Prakken (1972). The old hypothesis that partly colored seed phenotypes require the presence of a second factor e in addition to t, where the function of e is vague and unspecified, should be discarded for lack of supporting evidence, Under the new hypothesis, soldier series phenotypes (e.g., bipunctata, arcus, virgata, and virgarcus) may express in t ers Ers2 by action of ers or in t Ers Ers2 by action of various genes for partly colored seeds other than ers.
Magnetic Resonance Imaging (MRI) is currently considered as a nondestructive and noninvasive method for observing the distribution, concentration, and status of water in biological materials. However, effects of static magnetic fields of MRI systems on plant growth and development remain controversial. This study was conducted to investigate the water imbibition and radicle growth of Pisum sativum (cv. Little Marvel), Zea mays (cv. Pioneer 3379), and Glycine max (cv. Forrest) seeds oriented to four directions and exposed to six different magnetic field strengths commonly used in MRI systems.
Seeds were embedded in a water saturated synthetic foam medium, and were oriented, with respect to their hilum or embryo, to the east, south, west, or north. Seeds were then exposed to either 2, 4, 6, 8, 10, or 15 kilogauss static magnetic fields for 48 hours (water imbibition) or 54 hours (radicle growth).
The orientation of seeds and the magnetic field strengths had no effect on water imbibition or radicle growth of seeds tested. However, long term exposure retarded pea radicle growth in 2 KG treatment, enhanced soybean radicle growth in 10 KG treatment, but had no effect on corn radicle growth.
The involvement of the seed coat in low temperature germination of melon seeds was examined in two accessions differing in their ability to germinate at 14°C: `Noy Yizre'el' (NY) (a cold-sensitive cultivar) and `Persia 202' (P-202) (a cold-tolerant breeding line). Submerging the whole seed, or covering the hilum with lanolin, strongly depressed germination of NY, but not of P-202. Accessions differed in germination response to decreasing O2 concentration, with NY showing higher sensitivity to hypoxia. Intercellular spaces in the outer layer of the seed-coat were evident in the more tolerant P-202, while in the sensitive NY this layer is completely sealed. Sensitivity to hypoxia was greater at 15°C than at 25°C and was greater in NY than in P-202. It is proposed that the seed-coat imposed dormancy at low temperature in NY is the combined result of more restricted oxygen diffusion through the seed coat and a greater embryo sensitivity to hypoxia, rather than imbibition impairment or a physical constraint.
Abstract
During imbibition, water always follows the same pattern when entering the seed testa in semihard seeds (SHS) of snap bean (Phaseolus vulgaris L.). Water first enters the raphe and the chalazal region of the testa (R-CT), then migrates circumferentially along the midline of the seed, leaving the lateral faces the last to be fully imbibed. The R-CT region is the main site of primary uptake of both water vapor and liquid water by SHS. The hilum, micropyle, and strophiole play only a minor role in water uptake in SHS. In comparison to the readily permeable seeds of ‘Bush Blue Lake 47’, SHS have more total phenols in the osteosclereid cells and more pectic substances in the palisade cells of the CT. The presence of these compounds may account for the impermeable nature of SHS. Measurements made of palisade cell length and width in the R-CT region revealed that cell length increased and width decreased in the chalazal testa region (CT) as seed moisture content increased from 6% to 12%. It is proposed that semihardening of bean seeds is mainly a result of the reversible physical changes in the length and width of the palisade cells in the R-CT region. Seeds imbibe at high moisture content (12%) because the palisade cells have stretched, which allows water uptake. Seeds are impermeable at low moisture content (6%) because the palisade cells change in size and form a physical barrier to water movement.
Embryo abortion and empty seeds after self-pollination occur in some transgenic (ACO antisense) `Galia' male parental lines. An embryo-rescue system in this melon was developed to save potential viable embryos. To obtain the best and reliable embryo-rescue technique, several parameters were used including an improved (five new supplements) nutrient medium (named E-21) from the E-20A basic medium (Sauton and Dumax de Vaulx, 1987), an inoculation system (removing the embryo from the seed or intact seed), and the use of different fruit harvesting dates of the wild type and a transgenic `Galia' male parental line. Fruits of wild type (WT) and transgenic (ACO gene in antisense orientation) `Galia' male parental line were harvested at 4, 10, 17, 24, and 30 days after pollination (DAP). Fruits were surface sterilized by dipping in a 20% commercial bleach solution for 30 minutes. Subsequently, seeds were removed from fruit under sterile conditions. These seeds were either used to dissect the embryos or placed directly with the hilum facing E-20A or E-21 medium. Seedlings from all treatments were transferred to E-21 elongation medium, incubated 4 weeks, and transferred to soil to evaluate growth. The efficiency of this technique was greater when the time after pollination (4, 10, 17, 24, and 30 DAP) to rescue the embryos was increased. Thus, 30 DAP was the best time to rescue the embryos. The number of rescued embryos using E-21 medium was greater than with E-20A. We did not find any significant differences in survival efficiency rate between WT and transgenic embryos. We have obtained a competent embryo-rescue technique for WT and transgenic `Galia' male parental line, which can be applied to rescue valuable GMO hybrid-melon embryos.
stratification, 3) intact seeds without prior stratification imbibed in 100 µM gibberellic acid (GA 3 ), 4) intact seeds without prior stratification with the seedcoat split at hilum, 5) intact seeds without prior stratification with the seedcoat split at end
), whereas a conspicuous oval-shaped, slightly raised hilum is located on showy ticktrefoil ( Fig. 2B ). After 3 s of mechanical scarification, the seedcoat was abraded along the periphery of the seed and, sometimes, damage penetrated into the cotyledonary
‘Arima’ (left) and ‘Mipung’ (right) in late September. ‘Mipung’ has short and dense burs, dark brown nuts somewhat triangular in shape, good gloss, a nut height to nut width ratio of 0.79, and a hilum length to nut width ratio of 0.97 ( Fig. 2A