Seed dormancy and germination of Echinochloa oryzicola Vasing.: Dormancy-breaking mechanism of potassium cyanide

• Published in: Journal of Weed Science and Technology Vol. 33; no. 3; pp. 172 - 179
• Main Authors: Yamasue, Y. (Kyoto Univ. (Japan). Coll. of Agriculture), Hasegawa, R, Ueki, K
• Format: Journal Article
• Language: English; Japanese
• Published: The Weed Science Society of Japan 31.10.1988
• Subjects: ACIDE CYANHYDRIQUE; ACIDO CIANHIDRICO; AQUATIC WEEDS; CHEMICAL REACTIONS; DORMANCE; DORMANCY; DORMANCY BREAKERS; ECHINOCHLOA; HYDROCYANIC ACID; INTERRUPTORES DE LATENCIA; LATENCIA; MALEZAS ACUATICAS; MAUVAISE HERBE AQUATIQUE; POTASIO; POTASSIUM; REACCIONES QUIMICAS; REACTION CHIMIQUE; SUBSTANCE LEVANT LA DORMANCE
• ISSN: 0372-798X; 1882-4757
• DOI: 10.3719/weed.33.172

Dormancy-breaking mechanism of KCN in Echinochloa oryzicola seeds was studied by determining activities of respiration and redox enzymes in the seeds treated for 48hrs at the optimum concentration for breaking dormancy. KCN remarkably promoted germination of the seeds with primary dormancy. Any visible signs of germination were not observed during treatment, but started soon after seeds were transfered to the subsequent incubation without cyanide, indicating that the germination-induction was present during the 48hr treatment period. The KCN concentration causing the maximum germination at 100mM greatly inhibited both O2 consumption and cytochrome c oxidase activity. ADH activity of treated seeds initially decreased for 24hr, but thereafter increased. The RQ value increased to 3.6 during the germination-induction period, whereas fluctuations in neither ADH activity nor RQ value were observed in nontreated seeds. There was little difference in G6PDH activity between treated and nontreated seeds during treatment, but the treated seeds increased in activity as germination began. During the germination-induction period, catalase activity was remarkably inhibited by KCN, while, on the contrary, peroxidase was stimulated to activity two-folds higher than that of nontreated seeds. The amount of NAD (P) H in treated seeds significantly decreased soon after the subsequent incubation, suggesting the increased activities of NAD (P) H oxidases. The alternations observed in enzyme activities pointed out that the scheme HENDRICKS and TAYLORSON (1975) proposed for the mechanism of germination promotion for thiourea, nitrite and hydroxylamine was also applicable for KCN action in the seeds of E. oryzicola. The shift of aerobic respiration to alcohol fermentation by KCN was worthy of note since the latter is, as we previously reported, the main energy-yielding pathway of the rice paddy weed seed at early imbibition.