Copyright 1998-2017 Yoshiaki Yoneda
In all strains, the seeds are black. There is a reddish tinge to the hypocotyls, though some differences in lightness and shading are found between strains. There are many epidermal hairs to the upper half of the hypocotyls and cotyledonary petioles in Colombian Y023 and Y024, but almost no epidermal hairs in the TKS, Africa, Brazil, or Mexico strains.
The leaf is three-pointed in all strains, but there are large variations in form. The author divided the leaf form into five types. The main narrow lobe type leaf, which refers to the older Japanese names Tuneha and Namiba (ordinary leaf), has a narrow main lobe among strains of Ipomoea nil. TKS, Nepal, and Philippines have this type of leaves. The leaf of strain Africa has been referred to as retracted (or shaped like a sandy beach). As this form is assumed to be produced by the main lobe not to lengthen but to become wide, it is named the main lobe-wide type. Strains of Brazil, Mexico, and Iran have this type of leaves in addition to Africa. The main lobe-intermediate is found in strains of Colombian Y023, Y024, Y025, and Australia. The fourth leaf type is very unique. Found only in Colombian Y026, which has extremely minute side lobes and is cordate as a whole, leaves of this type sometimes grow a little longer than average. This type is called the side lobe-minute type. The fifth type is that of Peking Tendan, and it is called a triangle type because the lobes together form a triangle. This type resembles the juvenile form of leaf such as the first or second leaf of Ipomoea nil.
Leaf colors vary. On the one hand, strain Africa has an intensely green leaf, while on the other hand, strain Iran has a yellowish green leaf.
As for flower size, a diameter of 5 ~ 6 cm is ordinary, but the Australian Y028 strain has bigger flowers of more than 6 cm. The flower form is generally that of a funnel. The Colombian Y026 strain has slightly more slender flowers as a whole.
As for flower color, strains TKS and Mexican Y030 have blue flowers tinged with purple, but other strains are blue and differ in the lightness and shade of that color. Strains Africa, Brazil, Colombian Y025, and Australia have considerably light blue flowers. The flower of every strain reddens as it withers. Only TKS has a colored flower tube, probably because this characteristic is inherited from the parent chosen among the Japanese morning glory, Ipomoea nil.
Dichasium is the inflorescence of the morning glory; one flower (the second flower) grows in each axil of two bracteoles of the terminal flower, and then the next flowers grow in the axils of the second flower. However, it is rare to find five flowers per peduncle. Strains Philippines and Iran have one flower per peduncle. The strains with generally one but sometimes two flowers per peduncle are TKS, Peking Tendan, Nepal, Australia, and Mexico. Strains Colombian Y023, YO24, and Africa have more flowers, frequently two to four per peduncle. Strains Brazil, Colombian Y025, and Y026 have almost as many flowers.
Among these 13 strains, the high number of flowers per peduncle in the four Colombian strains, as well as in the Brazil and Africa strains, are considered to reflect the pre-cultivation characteristics of the morning glory. As for the leaf form, it is conceivable that the main lobe-narrow type of strains TKS, Nepal, and Philippines, as well as the main lobe-wide type of strains Brazil, Africa, Mexico, and Iran, are differentiated from the main lobe-intermediate type of strains Colombian Y023, Y024, Y025, and Australia. The relationship between these three-pointed leaf types and side lobe-minute type of Colombian Y026 is not understood. Epidermal hairs are observed from the cotyledonary petiole (connecting the cotyledons to the hypocotyl), to the upper part of the hypocotyl. Cotyledonary petioles of Colombian Y023 and Y024 have fairly many epidermal hairs, while strains TKS, Africa, Brazil, and Mexico have few or almost no hairs. If these characteristics are taken into account, the author thinks that strains Colombian Y023 and Y024 are interesting perspectives into the origin of the morning glory, Ipomoea nil.
As the strains vary considerably in morphological characteristics, the author crossed each strain with every other strain especially to examine the relationships between strains Africa and Brazil on the one hand and each of the other strains on the other hand. Preliminary results showed that most combinations including strains Africa and Brazil produced fruits.
Cultivated under natural conditions in Shizuoka-city, the early blooming type includes strains Peking Tendan and Iran, while the normal type includes TKS, Nepal, and Philippines; these five strains are local Asian ones. Other strains belong to the extremely late blooming type; Africa and Brazil begin flowering after the middle of September. Mexican Y030 flowers at the beginning of October. Flower buds are observed in October only in strain Australia and in the four Colombian strains. This reflects differences in the natural conditions between Shizuoka-city and the place where each strain originated, including differences in latitude.