Perennial and wild Triticeae in Japan, description and a short review on process of studies, investigations and results.

Mikio Muramatsu

Ezu-cho 3-6, Okayama-shi, 700-0028, Japan

Introduction

Species of the tribe Triticeae, Gramineae are widely distributed throughout the Japanese islands. However, since the islands are located far away from the center of the origin of the tribe, which is supposed to be the western part of the Asian continent, characteristics are expected to be differently differentiated. Besides remote geographical location, the Japanese climate might have contributed to their specialization. Nevertheless, the species found in Japan are thought to be very important. Here, I will describe as a short review the feature of the Japanese Triticeae species, regarding taxonomy and cytogenetics conducted at universities and institutions of Japan by 1990. I summarize especially, studies made by the Japanese researchers, reported mainly in Japanese language in domestic publications (research papers, reports, abstracts). In addition, the author wants to introduce ideas and propositions concerning taxonomy and cytogenetics results of investigations conducted for years.
Studies on the tribe Triticeae species in Japan would be divided into at least four different periods.
1. Identification of scientific names with Linnaean classification system in 1800's.
2. Establishment of the Triticeae flora in Japan after 1900-1940.
3. Interspecific cross hybridization, chromosome pairing studies in relation to the classification.
4. Hybridization studies using embryo-rescue, detailed analysis of the F1 and progenies.
According to a recent system, Japanese Agropyron,which was often treated as Roegneria, is included in Elymus. Nevertheless, for avoiding confusion, I will use the traditional species name mainly following Ohwi (1984), and I shall start with plant geographical point of view that will give some idea for the environment of the regions where the indigenous species were distributed.

I. Location of Japanese islands

Present-day Japan extends roughly from N45°of Hokkaido to the south N24°near the Tropic of Cancer. In comparison with European countries, Japan is located relatively south, equivalent to the Mediterranean area and to North Africa. The main parts of Japan belong to the warm temperate region. Because of the relative southern location, differences in the day length between summer and winter are less wide as compared with Europe. At Tokyo (N35°41') the summer day length is not as long as in many European cities.

II. General tendency of the climate of Japan and vegetation

Although the climate of the Japanese islands (archipelago) is generally mild and warm with predominating oceanic climate, it tends not to be always true. The Japanese archipelago is characterized by monsoon climate and is located in the area where cold and warm fronts are extended and are often hovering overhead. Especially the days around the summer solstice, it is a period of heavy precipitation called "Baiu" (the rainy spell in early summer) that lasts usually more than 40 days. After the heavy rainy season passes, except in the alpine region and Hokkaido, comes a tropical type of summer with humid and high air temperature. Islands are often hit by a typhoon, which is accompanied by heavy precipitation and strong wind of 25 meters per second, or higher. During the period of "Baiu" and following summer, introduced foreign plants not adapted tend to die out because of suffering by high temperature, less sunshine and high humidity, which reaches more than 70% up to 100%. Introduced Triticeae lines are not exceptions; it is usual to have severe difficulties in cultivation in experiment fields and often die without seed set.

Winters are severe in the different ways. Strong wind from Siberia, locating north-west across the Japan Sea, brings cold and the humid air when passes through on a warm sea current then hits high central backbone mountains and produces deep snow accumulation of meters for the mountain slope-side front of the Japan Sea, while it produces cold and dry weather for the Pacific Ocean side. It will be understood that, different from European countries, the Triticeae species must pass through both vegetative and reproductive phases within relatively short period by beginning June in Japan. However, this indicates, if we see from the different point of view, the species distributed in Japan have characters that are tolerated both by unfavorable seasons with typical Baiu,and are thought to be unique genetic resources.

Wolfe (1979) reported on the forests of Eastern Asia. The kind of forest that covers from the central Honshu to Shikoku and southern Kyushu, except high mountain' area, was termed the Notophyllous Broad-leaved Evergreen forest (oak-laurel forest). Then in the southern area next to there the Ryukyu Islands are covered by paratropical rain forests. Forests change to north in the following order: that is the Mixed Broad-leaved Evergreen and Coniferous, Mixed Mesophytic, Mixed Northern Hardwood, and Mixed Coniferous.

Vegetation areas of "Notophyllous Broad-leaved Evergreen" and "the Mixed Broad-leaved Evergreen and Coniferous" show almost equally the same with a forest termed "the warm-temperate evergreen (lucidophyll) forest" by Kira (1991), who considered the importance of the warmth index and high precipitations. Although I will keep in mind to discuss this in a separate paper in detail, there is some parallel distribution between the forest type and the species of Triticeae (For the Japanese species see Table 1 in a later chapter) showing a kind of habitat segregation.