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Nobuki Sasaki

Bio: Nobuki Sasaki is an academic researcher from Tohoku University. The author has contributed to research in topics: Germination & Oryza sativa. The author has an hindex of 6, co-authored 9 publications receiving 390 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a search for growth and germination inhibitors in rice husk (Oryza sativa L. cv Koshihikari) revealed four compounds, ineketone, S (+)-dehydrovomifoliol, momilactone-C and p -coumaric acid, in addition to the previously known motherilactones-A and -B.

133 citations

Journal ArticleDOI
TL;DR: In considering the breaking of dormacy in rice seeds, it may be neces-sary to check the interaction between momilactones and GA or IAA which has an important role during rice seed germination.
Abstract: In order to isolate growth and germination inhibitors from the hulls of dormant rice seeds, the seeds of a Japonica cultivar 'Koshihikari' and an Indica one 'Surjamukhi', which have strong dormancy, were used. The rice hull (ca 200kg) was soaked in 80% methanol for about 2 months. The methanol extracts were concentrated to an aqueous phase by the flash evaporator at below 40°C. The aqueous phase was extracted with chloroform and the active fraction was moved in chloroform. The active chloroform fraction was successively fractionated by organic solvents : n-hexane, benzene, ether, ethylene chloride, and ethyl acetate. The biological activity of each extract was checked by lettuce germination test. The active fraction checked was further separated according to solubility in dilute acid or base. The neutral fraction of benzene and ether extracts showed a strong inhibitory activity. The active fraction was used for further chromatographic study. By the silica gel thin layer chromatography with a developing solvent, benzene : ethyl acetate (10 : 1), two active compounds were crystallized and were identified as momilactone-A (C20H2603) and -B (C20H26O4) The momilactones inhibited the seed germination and the seedling growth of rice and lettuce at a concentration of 10-3M. Especially, these substances remarkably inhibited the root growth of rice seedling at 10-5-10-3M. Momilactone-B had stronger inhibition than momilactone-A. The inhibitory activity of momilactone-B was similar to that of a typical growth regulator, abscisic acid. 'Koshihikari' contained more momilactone-A than momilactone-B, while 'Surjamukhi, which has stronger dormancy than 'Koshihikari', held more mornilactone-B than momi-lactone-A. It was supposed that the content of momilactone-A and -B in rice seeds might vary with the rice cultivar. The inhibitory activity of momilactones was partially reduced by GA3 or IAA. In considering the breaking of dormacy in rice seeds, it may be neces-sary to check the interaction between momilactones and GA or IAA which has an important role during rice seed germination.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the germination inhibitors in parsley seeds using the aid of a germination assay with lettuce seeds and revealed that one of the inhibitors was heraclenol.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the structure of momilactone-C (M-C), a minor constituent of growth inhibitors in rice husk, was determined by X-ray analysis, which revealed that C9-C10 of M-C was unusual cis configuration having a boat conformation of A ring.
Abstract: Structure of momilactone-C (M-C), a minor constituent of growth inhibitors in rice husk, was determined by X-ray analysis, which revealed that C9–C10 of M-C was unusual cis configuration having a boat conformation of A ring. The stereochemistry of C9 of previously reported momilactone-A and B (I and II) has been erroneously written and should now be revised to β -configuration with respect to hydrogen atom as in M-C.

18 citations


Cited by
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Journal ArticleDOI
TL;DR: The most recent advances in the chemicals disclosed, their mode of action and their fate in the ecosystem are pointed out and attention will be paid to achievements in genomics and proteomics, two emerging fields in allelopathy.
Abstract: Allelopathy studies the interactions among plants, fungi, algae and bacteria with the organisms living in a certain ecosystem, interactions that are mediated by the secondary metabolites produced and exuded into the environment. Consequently, allelopathy is a multidisciplinary science where ecologists, chemists, soil scientists, agronomists, biologists, plant physiologists and molecular biologists offer their skills to give an overall view of the complex interactions occurring in a certain ecosystem. As a result of these studies, applications in weed and pest management are expected in such different fields as development of new agrochemicals, cultural methods, developing of allelopathic crops with increased weed resistance, etc. The present paper will focus on the chemical aspects of allelopathy, pointing out the most recent advances in the chemicals disclosed, their mode of action and their fate in the ecosystem. Also, attention will be paid to achievements in genomics and proteomics, two emerging fields in allelopathy. Rather than being exhaustive, this paper is intended to reflect a critical vision of the current state of allelopathy and to point to future lines of research where in the authors' opinion the main advances and applications could and should be expected.

415 citations

Journal ArticleDOI
TL;DR: A new challenge that exists for future plant scientists is to generate additional information on allelochemical mechanisms of release, selectivity and persistence, mode of action, and genetic regulation so as to further protect plant biodiversity and enhance weed management strategies in a variety of ecosystems.
Abstract: Allelopathy can be defined as an important mechanism of plant interference mediated by the addition of plant-produced secondary products to the soil rhizosphere. Allelochemicals are present in all types of plants and tissues and are released into the soil rhizosphere by a variety of mechanisms, including decomposition of residues, volatilization, and root exudation. Allelochemical structures and modes of action are diverse and may offer potential for the development of future herbicides. We have focused our review on a variety of weed and crop species that establish some form of potent allelopathic interference, either with other crops or weeds, in agricultural settings, in the managed landscape, or in naturalized settings. Recent research suggests that allelopathic properties can render one species more invasive to native species and thus potentially detrimental to both agricultural and naturalized settings. In contrast, allelopathic crops offer strong potential for the development of cultivars that are ...

399 citations

Book ChapterDOI
TL;DR: In the twelve years since the first review article dealing with chemical constituents of the Hepaticae appeared in this series as Volume 42 (19), several short reviews concerned withchemical constituents of bryophytes have been published.
Abstract: In the twelve years since the first review article dealing with chemical constituents of the Hepaticae appeared in this series as Volume 42 (19), several short reviews concerned with chemical constituents of bryophytes have been published (22, 96, 144, 265, 271, 647, 649, 650) In 1988, a Symposium on Chemistry and Chemical Taxonomy of Bryophytes was organised on the behalf of the Phytochemical Society of Europe; the proceedings of this meeting appeared as a book entitled Bryophytes: Their Chemistry and Chemical Taxonomy (651) The symposium concerned itself with phytochemical, biochemical, botanical, chemotaxonomical, pharmaceutical, biotechnological and environmental aspects of bryophytes as well as with the synthesis of the terpenoids and aromatic compounds bryophytes elaborate The physiological and biochemical aspects of bryophytes have also been described in a recent book Bryophytes Development: Physiology and Biochemistry (139)

291 citations

Journal ArticleDOI
TL;DR: The potent biological activity of the “ancestral” gibBerellins, which has led to the independent evolution of distinct gibberellin biosynthetic pathways in plants, fungi, and bacteria, is further discussed as an archetypical example of the selective pressure driving the observed diversification of the large super-family of labdane-related diterpenoid natural products.

274 citations

Journal ArticleDOI
TL;DR: The possible role of phytoalexins in the resistance of rice plants against the fungus Pyricularia oryzae (= Magnaporthe grisea) is discussed, and the future prospects ofphy toalexin research are outlined.

257 citations