Plant World 9(10): 247 (October, 1906)

THE GERMINATION OF THE MORNING GLORY

Mary Ellen Tayler

An article in the Botanical Gazette for August, 1905, by Professor Beale, suggests certain germination experiments which were undertaken by the writer upon the seeds of our common morning glory, Ipomoea purpurea (L.) Roth, in connection with the study of the development and morphology of that species. In the unripe seed the embryo is bright green, but as the seeds ripen the embryo becomes yellowish or whitish. Characteristic leaf structures, such as palisade parenchyma and stomata, are present in the cotyledons before germination. Large spherical cavities filled with latex are found in the parenchyma, as has been reported for Convolvulus major by Turnbull. Whether the chlorophyllous cotyledons with their leaf-like structure and the storage of latex are ready for germination without further maturation and a period of rest is a question which can be answered only by experimentation. To obtain some light upon the subject, seeds of the morning glory, varying in age and maturity, were planted in garden soil and observations were recorded upon their germination. The table below sums up these experiments.

Condition of the Seeds Number
Planted
Number
Germinated
Days in
Germination
Per Cent.
Germinating
Fresh and green 104 41 26 39
Green, air dried until white 58 16 22 27
Mature, but no period of rest 90 76 15 83
Dry, after a period of rest 60 17 8 28
Immature (1903) rest of 8 mos. 25 16 8 64
Mature (1903) rest of 12 mos. 100 97 8 97
Mature (1893) rest of 10 years 100 25 8 25

Further, plants grown in a green-house from immature green seeds blossomed earlier, had shorter stems and produced fewer seed-pods by about one-half than did those raised under the same conditions from seeds having no chlorophyll in the embryo. When the plants so grown from immature green seeds had ceased to blossom, those raised from mature colorless seeds were thrifty and still forming buds and maturing flowers and fruit. Both kinds of seeds were planted at the same time.

From the facts demonstrated above, certain conclusions may be drawn. (1) Giving a resting period to the fully ripe seed shortens the time required for germination. (2) Drying green seeds shortens their period of germination. (3) Dry, mature seeds having no chlorophyll germinate more quickly than fresh green seeds. (4) Fully matured and rested seeds germinate in eight days or less, whether the period of rest be eight months, a year, or ten years. (5) Twenty-five per cent. of matured seeds retained their vitality for ten years. (6) The highest per cent. of germination occurs in seeds one year old. (7) Seeds ripen earlier upon plants grown from unripe seeds, but the vegetative parts are more scanty and the amount of fruit less than upon plants grown from matured seeds.


CybeRose note: It seems to me that plants raised from unripe seed would be more useful as pot plants. One may ensure continuity of bloom by starting a second batch a few weeks after the first.