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Seed development and ripening in temperate grasses 5. seedling vigor in italian rye grass and lolium multiflorum perennial rye grass lolium perenne seeds during development and ripening under different temperature conditions

Shimizu, N.; Komatsu, T.

Sochi Shikenjo Kenkyu Hokoku 17: 76-86

1980


Accession: 006378228

The present investigations were undertaken to elucidate the seedling vigor in Italian ryegrass and perennial ryegrass seeds harvested at various stages during development and ripening under 2 different temperature conditions (High = 15.degree. C to 25.degree. C, Low = 10.degree. C to 20.degree. C). To determine seedling vigor, the seeds were grown under natural environmental conditions during Sept.-Nov. and criteria for seedling vigor, such as 1st leaf length, number of tillers, number of leaves, plant height, leaf area, leaf weight, stem weight, plant top weight, leaf weight ratio and specific leaf area, were measured at the 3rd, 5th and 7th week after emergence. In both Italian ryegrass and perennial ryegrass, seedling emergence was dependent on the developmental stage of the seed. Seedling emergence and survival seedlings were observed in the seeds on and after the second developmental stage under any temperature conditions at development and ripening. In both Italian ryegrass and perennial ryegrass, 1st leaf length showed significant difference between the seeds harvested at various stages during development and ripening under high and low temperature conditions, while there were no significant differences in leaf wt ratio and specific leaf area. The growth increment characters such as leaf area, leaf weight, stem weight and plant top weight, showed highly significant differences between the seeds harvested at various stages during development and ripening under high and low temperature conditions in Italian ryegrass and under low temperature condition in perennial ryegrass. No character showed significant difference between the seeds under high temperature condition in perennial ryegrass. In order to define the relationships between seedling vigor and the developmental stage of seed, cluster analyses were applied to the seeds harvested at various stages during development and ripening under high and low temperature conditions in Italian ryegrass and under low temperature condition in perennial ryegrass, using the measurements of the characters showing significant differences. The seeds at the identical stage of development and ripening, except for the 4th stage, were tightly clustered, under any temperature conditions in Italian ryegrass and perennial ryegrass. The seedling vigor of the seed at the second development stage were very poor and a satisfactory seedling vigor was obtained in the seeds on and after the latter 1/2 of the third developmental stage, when the seed reached a maximum weight and a full size of embryo. In the identical developmental stage, the seed under low temperature condition at development and ripening produced more vigorous seedlings than the seed under high temperature condition, when using plant top weight as the criterion for seedling vigor. The characters showing significant difference between the seeds harvested at various stages during development and ripening, such as 1st leaf length, plant height, leaf area, leaf weight, stem weight and plant top weight, were positively and significantly correlated with the seed weight and embryo length within the seeds under high and low temperature conditions at development and ripening in Italian ryegrass and under low temperature condition in parennial ryegrass.

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