Moisture and temperature requirements for germination of three annual species of Medicago

Abstract

Moisture and temperature requirements for germination were determined for Medicago polymorpha L. var. vulgaris (Benth.) Shin., M. minima (L.) Bart., and M. truncatula Gaertn. Water absorption by seeds of all species was very rapid during the first two hours after which relatively little additional water was taken up until radicles emerged. Initial rate of imbibition was fastest in M. minima and slowest in seeds of M. polymorpha. Under favourable conditions radicles emerged in about twelve hours when seeds had imbibed from about two to three times their original weight of water. Over the range of 0-12 atmospheres of osmotic pressure, increasing the tension had depressed germination of M. pobmorpha whereas an increase from 0 to 3 atmospheres stimulated germination of M. minima. From temperatures of 15¦ to 30¦C, M. polymorpha germinated best in the lower, M. truncatula in the intermediate, and M. minima in the higher range.