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with 14.8% MC were used (Seed Lot 2). The hilum of the seeds was covered by a layer of Vaseline, and the seeds were placed in a petri dish inside an electronic humidity control box set at 3% RH. To prevent the seeds from rolling around and having

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The germination of verbena (Verbena × hybrids) seed was found to be sensitive to high substrate moisture content. Cultivars varied in sensitivity to excessive substrate moisture content, with `Romance Scarlet' having higher total germination (G) in the presence of free water than `Showtime Blaze' or seedling `Red A'. Hilum cavity measurements of dry seeds showed larger hilum apertures with reduced depths for seeds of `Romance Scarlet' than for the others. Seed imbibition resulted in a rapid and extensive thickening of the hilum wall. The extent of hilum aperture closure varied among cultivars and the quantity of water present. Free water reduced hilum apertures 45% for `Romance Scarlet', 60% for `Showtime Blaze', and 86% for `Red A'. Seeds of `Romance Scarlet' and `Showtime Blaze' failed to germinate with lanolin covering the hilum, while seeds coated with lanolin, except for the hilum, had 67% to 78% G of nontreated seeds. This difference indicates that essential oxygen for the embryo was obtained through the hilum and micropyle of the seeds. Total germination varied with substrate moisture content, with seeds placed horizontally on 2%, 1%, or 0.5% agar having 80%, 75%, and 65% germination, respectively, for `Romance Scarlet' and 59%, 41%, and “24%, respectively, for `Showtime Blaze'.

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Abstract

Variations occurred in the rate of water uptake of seeds of different dry bean cultivars (Phaseolus vulgaris L). ‘Pinto UI11’ had a higher water uptake by 24 hours than the other 6 cultivars. The micropyle was the main site for water entry in white-seeded ‘Great Northern’ and it is inferred that the raphe and or hilum areas were mainly involved in water uptake in ‘Pinto UI11’. No water uptake through the seed coat of seeds of 7 cultivars occurred by 2, 4, or 8 hours and only a small amount by 24 hours, except ‘GN Star’ where no water uptake was noted indicating that it had an impermeable seed coat during that period.

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-Berman et al., 1989 ), the hilum was found to be the main pathway for gas exchange, and sealing the hilum prevented germination because oxygen diffusion through the seedcoat surface was not sufficient. Similar results were reported in ‘Noy Yizre'el’ (NY

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Verbena (Verbena × hybrida Voss) seed germination varied with the water content of the substrate. Total germination percentages (G) were highest when substrates were 75% to 100% saturated and progressively declined with increased free distilled water (FDW) on the blotter paper substrate. Natural differences in G among cultivars at favorable substrate moisture levels increased when free water was present. Removing the seed hilums did not increase G of `Romance Scarlet' on a substrate with FDW, but significantly increased the G of `Showtime Blaze' and `Red A'. Au inverse relationship was found between seed moisture contents and G at high substrate moisture levels. `Romance Scarlet', `Showtime Blaze', and `Red A' had 64%, 73%, and 84% seed moisture contents and G of 72%, 18%, and l0%, respectively. The period of sensitivity to excessive water during germination was day 2 for `Red A' and days 2 and 3 for `Showtime Blaze'. The G of `Romance Scarlet' seed was not reduced when placed on a substrate containing FDW for 1 day. Removal of seed hilums from `Red A' significantly increased G during day 2 for seeds on a substrate containing FDW.

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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.

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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.

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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.

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), 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

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‘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

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