The presence of two types of /^-cyanoalanine synfhase in germinating seeds and fheir responses to ethylene. -Physiol. Plant. 93: 71.3-718.Germinafine seeds of many species contain fwo fypes of /i-cyanoalanine synthase (CAS. EC 4.4.1.9) thaf conveii HCN fo /?-cyanoa'lanine. One is cyfoplasmic CAS (cyt-C.AS), which is precipitated by 50 lo 609r (NHai^SO^ and has a pH optimum of 10.5. Cvtoplasmic C.^S is present at high levels in dry seed and its activity does nof increase during imbibition. The activity ot cyt-CAS is uot affected by exogenously applied efhylene (CjHji. except in riee (Or\~a sativa cv. Sasanishiki). The second fype of CAS ftiuud in seed is mitochondrial CAS (mit-CAS I. which is precipifated by 60 fo 1()''« (NHjl:SO4 and has a pH optimum of 9.5. Mitochondrial CAS is present at low levels iu dry seed, and its activity increases greatly during imbibition in the seeds of ali species fested. Exposure fo C:H^ stimulated mit-C.i^S activity in seeds of rice, barley (Hordeum yidgare cy, Hadakamugii, cucumber (Cucumis satiyus cv. Kagafushinari) and cocklebur {Xanihhmi pennsyhamcum). The increase in fhe mit-CAS activity in cocklebur in response to C^Hj ccmimeticed after a fag period of 2 to 3 h when fhe duration of soaking was short (16 hi. but commenced without a lag period when fhe seeds were soaked lor Ihree mouths. Application ot bofh chioramphenicol aud cycloheximide to the axial and eotyledonary tissues of cocklebur seeds strongly inhibifed growth as well as fhe increase in mit-CAS acfivity. It is postulated fhal the mit-CAS is syuthesized de noi-o dtiring imbibition and thai ifs acfivity is regulated by C;H4. CO;, vvhich also promotes seed genninatiou in some species. v»as ineffective in stimulating tnif-C.AS activity iu cocklebur seeds.
The presence of two types of /^-cyanoalanine synfhase in germinating seeds and fheir responses to ethylene. -Physiol. Plant. 93: 71.3-718.Germinafine seeds of many species contain fwo fypes of /i-cyanoalanine synthase (CAS. EC 4.4.1.9) thaf conveii HCN fo /?-cyanoa'lanine. One is cyfoplasmic CAS (cyt-C.AS), which is precipitated by 50 lo 609r (NHai^SO^ and has a pH optimum of 10.5. Cvtoplasmic C.^S is present at high levels in dry seed and its activity does nof increase during imbibition. The activity ot cyt-CAS is uot affected by exogenously applied efhylene (CjHji. except in riee (Or\~a sativa cv. Sasanishiki). The second fype of CAS ftiuud in seed is mitochondrial CAS (mit-CAS I. which is precipifated by 60 fo 1()''« (NHjl:SO4 and has a pH optimum of 9.5. Mitochondrial CAS is present at low levels iu dry seed, and its activity increases greatly during imbibition in the seeds of ali species fested. Exposure fo C:H^ stimulated mit-C.i^S activity in seeds of rice, barley (Hordeum yidgare cy, Hadakamugii, cucumber (Cucumis satiyus cv. Kagafushinari) and cocklebur {Xanihhmi pennsyhamcum). The increase in fhe mit-CAS activity in cocklebur in response to C^Hj ccmimeticed after a fag period of 2 to 3 h when fhe duration of soaking was short (16 hi. but commenced without a lag period when fhe seeds were soaked lor Ihree mouths. Application ot bofh chioramphenicol aud cycloheximide to the axial and eotyledonary tissues of cocklebur seeds strongly inhibifed growth as well as fhe increase in mit-CAS acfivity. It is postulated fhal the mit-CAS is syuthesized de noi-o dtiring imbibition and thai ifs acfivity is regulated by C;H4. CO;, vvhich also promotes seed genninatiou in some species. v»as ineffective in stimulating tnif-C.AS activity iu cocklebur seeds.
The mechanism of emergence from primary dormancy, the process of after‐ripening, in cocklebur (Xanthium pennsylvanicum) seeds was examined in relation to the involvement of volatile compounds and to the relative humidity (RH) in which the seeds were stored. The after‐ripening of these seeds proceeds only at water contents between 7 and 14% which are conditioned under RHs of 33% to 53% and are identified with water‐binding region II. After‐ripening of cocklebur seeds occurred even in water‐binding region I. imposed by 12% RH. when exposed to HCN gas during the storage period. Exposure of dormant seeds to acetaldehyde (ethanal) retarded after‐ripening. even in water‐binding region II. thus decreasing germinability. This decrease of germinability by ethanal was found also in the after‐ripened seeds, suggesting that ethanal accelerates seed deterioration rather than retarding the after‐ripening. The contents of ethanal. ethanal and HCN were high only in the dormant seeds held at 12% RH. Regardless of RH. a possible conversion of ethanal to ethanol. perhaps via alcohol dehydrogenase. was far larger in dormant than in non‐dormant seeds. In contrast, the reverse conversion of ethanol to ethanal was more profound in non‐dormant seeds. Pre‐exposure of both types of seeds to HCN reduced the contents of both ethanal and ethanol at 12% RH. The contents of various adenylales including ATP in seed tissues were higher in dormant seeds stored at 12% RH than in non‐dormant seeds after‐ripened at 44% RH. It is suggested that emergence of cocklebur seeds from primary dormancy by HCN treatment at 12% RH may result from the reduction in the contents of ethanal via an unknown mechanism incurring the consumption of ATP. This implies involvement of volatile compound metabolism at the water‐binding region II in the after‐ripening process of cocklebur seeds.
Amnesic shellfish poison ASP is regarded as one of the shellfish poison groups in the EU, though it is not subject to regulation in Japan. We have developed an analytical method of ASP based on the report by Hatfield et al. and other methods. Validation studies were carried out with certified compositional reference materials CRM . Performance parameters were estimated based on 17 analytical results. The estimate of trueness was 97.5 , and the estimate of intralaboratory reproducibility RSD was 1.5 . The HorRat r value was 0.16. These performance parameters meet the criteria in the Codex Procedural Manual. Furthermore, internal quality control was performed by using the CRM. The action limits were set based on the performance parameters of the method. Most of the results of the internal quality control were within the action limit range. The results confirmed that the quality of the analyses was well maintained. The purpose of the analytical method is to confirm that the level of ASP in scallop is less than 4.6 mg/kg. The applicability of the analytical method to scallops was confirmed by using spiked samples.
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