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EIJI TANESAKA EIKO UMEDA MASAYUKI YAMAMOTO KYOJIRO MASUDA KYOJI YAMADA MOTONOBU YOSHIDA 《Weed Biology and Management》2012,12(2):91-97
Sesamum mulayanum is a wild relative of cultivated sesame, Sesamum indicum, and sometimes grows in sesame crop fields as an associated weed. This species shows deep seed dormancy and is characterized by conspicuous purple pigmentation on the lower lip of the corolla. The present study examined the inheritance mode of seed dormancy by using reciprocal progeny from crosses between the two species. The seeds of S. indicum and F1 (S. indicum×S. mulayanum) showed good germination, but those of S. mulayanum and F1 (S. mulayanum×S. indicum) showed deep dormancy. The F2 seeds from both reciprocal crosses showed deep dormancy. These results, combined with the maternal inheritance of seed‐coat characteristics, indicated that the seed dormancy of S. mulayanum can be attributed to its seed‐coat structure (coat‐enhanced dormancy). The F3 (S. indicum×S. mulayanum) seeds varied in their depth of seed dormancy and those seeds with deep dormancy (<50% germination) and those with no or shallow dormancy (≥50% germination) occurred in the expected ratio of 3:1, indicating that this trait is polygenic but is controlled by a single dominant major gene. The purple pigmentation of the corolla was expressed in both reciprocal F1 plants and the presence and absence of pigmentation was segregated among the F2 plants at the expected ratio of 3:1, indicating that this trait is also controlled by a single dominant gene. The segregation of the major gene controlling seed dormancy and that controlling purple pigmentation was not independent (9:3:3:1), indicating that these genes are linked, providing insights on sesame domestication. 相似文献
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MASAYUKI YOSHIDA YASUHIKO MUROCHI YOSHIHIKO BABA KAZUMASA UEMATSU 《Fisheries Science》2002,68(2):277-281
ABSTRACT: A new method for monitoring spinal motoneuron activities during fictive swimming in teleost fish was developed. Enamel-insulated copper wire electrodes were implanted in the trunk muscle of goldfish or carp. For each freely moving fish, an electromyogram (EMG) was recorded using the electrodes. In those fish paralyzed with curare, using the same electrode set, bursts of electrical activities consisted of spikes of smaller amplitude and of shorter duration compared with those recorded by EMG. Simultaneous recording of the extracellular activity and intracellular recording from the muscle revealed that the bursts of spikes recorded in the paralyzed fish were motor nerve impulses innervating the muscle and are considered to be fictive swimming activity. The method developed in the present study provides a useful tool with which to investigate neuronal mechanisms underlying swimming activity in teleost fish. 相似文献
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MINORU ICHIHARA HIDEHIRO INAGAKI KAZUO MATSUNO CHIEKO SAIKI MASAYUKI YAMASHITA HITOSHI SAWADA 《Weed Biology and Management》2012,12(3):131-135
The potential impact of postdispersal seed predation by the field cricket, Teleogryllus emma (Ohmachi et Matsuura), on the seedling emergence of Italian ryegrass (Lolium multiflorum Lam.), a non‐native grass weed in Japan, was determined. The relationship between cricket density and the proportion of seedling emergence was investigated by conducting manipulative experiments in duplicate, using enclosures. One‐thousand seeds of Italian ryegrass were exposed to adult crickets at different densities (zero, one, two, four and eight individuals per 2.25 m2 enclosure) for 2 weeks. The proportion of seedling emergence decreased with increasing cricket density. The proportion of seedling emergence in the enclosures without the crickets was 90.9–97.2%, whereas the seedling emergence in the enclosures with eight crickets greatly decreased, to 0.5–2.5%. These results suggest that postdispersal seed predation by T. emma can substantially decrease the abundance of Italian ryegrass at an early life stage and reduce its population in environments with a high density of crickets. 相似文献
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MASAYUKI IWAHASHI YUTAKA ISODA SHIN-ICHI ITO YOSHIOKI OOZEKI SATOSHI SUYAMA 《Fisheries Oceanography》2006,15(2):125-138
Since there have been practically no surveys of the eggs of Pacific saury (Cololabis saira) in the western North Pacific (WNP), its spawning ground (SG) distribution has been poorly resolved, based mainly on the larval distribution. This means of estimating SG distribution is imprecise because saury eggs drift for more than a week before they hatch, in a region with intense western boundary currents and their extensions. To improve our understanding of the immature saury, a large number of larvae (body length <25 mm) collected in the WNP during 1993–96 were numerically backtracked to take into account the advection by geostrophic and wind‐forced Ekman currents, and the SG locations and ambient sea surface temperatures (SSTs) for the eggs and larvae on the backtracking trajectories were estimated. The resulting seasonal distributions of SGs indicated that both the locations and the intensities of spawning change from season to season. Moreover, the ambient SSTs for eggs just after fertilization ranged from a high of around 21.5°C in early autumn (September to October) to a low of around 15.0°C in late spring (May to June) with an intermediate of around 20.0°C in winter (January to February). The ambient SSTs showed seasonally different gradients while the individuals developed from eggs to early larvae: the SSTs decreased throughout the autumn (September to December), stayed rather constant in winter (January to February), and increased throughout the spring (March to June). The ambient SSTs for the early larvae were at around 19.0°C in autumn and winter (September to February) and around 16.5°C throughout the spring (March to June). 相似文献
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In this study, we examined the genetic diversity in three populations of the critically endangered annual, Bidens cernua, in Japan by using inter‐simple sequence repeat markers and compared our data with those from two common congeners: Bidens radiata var. pinnatifida and Bidens tripartita. In contrast to our expectations, the degree of genetic diversity at the species level was higher in B. cernua than in B. radiata var. pinnatifida or B. tripartita. At the population level, the degree of genetic diversity was highest in B. cernua. These results may be ascribed to the mating system and method of seedbank formation in B. cernua. An analysis of molecular variance revealed relatively high genetic differentiation among the populations of all three species. We concluded that the distribution width could not be an index of genetic variability in Bidens examined in this study. 相似文献
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MINORU ICHIHARA MASAYUKI YAMASHITA HITOSHI SAWADA YOICHI KIDA MOTOAKI ASAI 《Weed Biology and Management》2009,9(3):217-224
Italian ryegrass ( Lolium multiflorum Lam.) is an exotic winter annual weed that recently has seriously infested wheat fields in central Japan. To understand the influence of tillage systems on the germination ecology and seedbank dynamics of naturalized Italian ryegrass, we compared the fate of the seeds that were after-ripened in the soil with that of the seeds on the soil surface, and then examined the germination characteristics of the seeds retrieved from both treatments by germination tests in both a light/dark (12 h photoperiod) condition and in constant darkness. The seedling emergence was greater initially for the seeds after-ripened on the soil surface than for the seeds in the soil. The component of emergent seeds after-ripened on the soil surface increased as time passed during the summer, whereas that of emergent seeds in the soil scarcely increased. This contrasting emergence was, in part, attributable to the ability of the seeds to germinate at higher temperatures in the light/dark condition than in constant darkness. These results suggest that untilled systems, which leave many seeds on the soil surface, might promote the rapid depletion of Italian ryegrass seeds through germination before wheat sowing in early winter. In contrast, seed burial by tillage might inhibit the germination of the seeds and form a large transient seed bank available to germinate during the wheat-growing season. 相似文献
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