The 18th century was a peaceful era in Japan, during which a unique horticultural culture has developed. Boku-han, a cultivar of Camellia japonica, is a mutant in which stamens are transformed into white petaloids. Because pistils are complete and fertile, this cultivar has been often used as a parental line for breeding. This cultivar was formerly described in a catalog of horticultural plants in Edo (ancient Tokyo) in 1719. Owing to the strong contrast between the deep crimson red petals and the white petaloids, and in addition to its slender, delicate branching nature, Boku-han has been appreciated by many flower lovers and has been widely spread in Japan. Now Boku-han is also named as “Gakko” or moonlight, in the western part of Japan. Photographed by Hirokazu Tsukaya (Univ. Tokyo) in Kamakura, Japan, in 11 March, 2012 (Pentax Optio W80).

Photographed by Hirokazu Tsukaya (Univ. Tokyo) in Kamakura, Japan, in 11 March, 2012 (Pentax Optio W80).

In rain tropics, river bank is exceptionally good place for plants in terms of the availability of sun light. If you enter in rain forests, you will find that sun light is mostly absorbed by multilayered tree leaves from 40-m-high to a few-m-high. River bank is different. It is an open place and plants can enjoy sun shine there, although frequent floods suffer the area. If some mutations enable a particular strain of plants to have narrow leaves and strong roots, such strain is expected to tolerate the floods and can occupy the open area. It seems that occurrence of such mutation is not rare. Here is such a variant of an orchid, Arundina graminifolia. This species originally has narrow leaves (as the latin name “graminifolia” means: “having rice-family-like leaves”), but the variant adapted to the flood environment has much narrower leaves (less than half in width) that typically shows the evolutionary trend of plants to live along river bank. What genes are involved in this type of evolution? Trials to solve it are now on going in several laboratories.

Photographed by Hirokazu Tsukaya (The University of Tokyo) in Betung-Kerihun National Park, West Kalimantan, Borneo, in 26 December, 2011 (Pentax Optio W80).

The papaya is the fruit of Carica papaya L., a member of the family Caricaceae, which is widely grown in tropical and subtropical regions of the world. e yellow orange, ripe fruits are edible and rich in vitamins, minerals, and ber, while green unripe fruits are known to rich sources of papain, an enzyme used as a component of meat tenderizers and so on. In this issue Retuta et al. (Page 339) carried out the evaluation of selected transgenic papaya lines which are resistant to papaya ringspot virus. e hermaphrodite fruits are pyriform in shape (front row), while the female fruits are rounded in shape (second row).

Anagallis arvensis L., with its characteristic deep blue petals, distributes very widely in subtropics and tropics. Its preference of seashore ambient might have helped this species to distribute so widely. Although seeds are too small to be dispersed by an ocean current, capsules being rather tough and light in weight, may enable the seeds inside to dri without severe damages. A. arvensis is also well-known to accumulate the blue pigment, anthocyanin, in the petal cells, in a unique manner. If you examine these tiny petals under a microscope, there you will observe unexpectedly beautiful images.

Photographed by Hirokazu Tsukaya (The University of Tokyo) in Yakushima Island, in 16 May, 2010 (Pentax Optio W80).

A tree of Jatropha curcas L., with bunches of developing fruits. Matured fruit contains 2-4 grains of seeds, which serve as a rich source of triacylglycerol for biodiesel production.

Photographed at campus of the University of e Ryukyus by Prof Yoshinobu Kawamitsu.

Zelcova serrata (Thunb.) Makino is distributed in Japan, as well as in China, Korea, and Taiwan. Nevertheless, this species is often seen as a tree typically representing forest vegetation of Kanto Plain of Japan, partly because this species has been preferentially planted along streets and in parks. This tree shows a characteristic and beautiful branching pattern; a wonderful colorations in Spring, Summer and Autumn, respectively; and supplies us with good quality wood. Bonsai, a Japanese art of horticulture, also loves to try to reproduce the elegant tree figure on a small pot. For this species the sprout season is also the season of full bloom, although not obvious due to the greenish coloration of flowers.

Photographed by Hirokazu Tsukaya (Univ. Tokyo) in Hongo campus, the University of Tokyo, Japan, in 13 April, 2011 (Pentax Optio W10).