Finding and Visualizing Some Unknown Natural Phenomena in Carnivorous Plants by Tissue Culture

Katsuhiko Kondo¹, Yoshikazu Hoshi¹, Sayuri Ichiishi², Tsukasa Iwashina³, Hiroshi Kajita¹, Yusuke Kondo², Toshiharu Nagamitsu², Norikazu Tagashira¹

¹ Laboratory of Plant Chromosome and Gene Stock • Graduate School of Science • Hiroshima Univ. • 1-4-3 Kagamiyama • Higashi-Hiroshima City 739-8526 • Japan

² Plant Bio-technology Section • Sanmei Electric Co., Ltd.

³ Tsukuba Botanical Garden • National Science Museum

During the courses of plant tissue cultures in our Laboratory, we have found some unknown, peculiar phenomena especially in organogenesis and morphogenesis, new secondary metabolites, purified clone materials for DNA analyses, and so on. For instance on organogenesis and morphogenesis, if plants of Drosera ordensis in the D. petiolaris complex cultured in vitro were cut longitudinally a half by a razor blade and were continuously cultured in vitro, they generated and recovered the other side being surprisingly D. petiolaris. The mechanism of this morphogenesis change has been unknown and is expected to be clarified. Drosera ordensis and D. petiolaris may be taxonomically placed in the same species or category.

The second instance is in the cultured Drosera peltata and many other tuberous species of the genus: Top-tips of the plant shoots often produced white or sometimes green color globular-shaped tubers or sometimes elongated ones with many scales on air. Thus, tuberous species of the genus seemed not to respond to the force of gravity and to have basically top and bottom of their shoots mixed up. This phenomenon suggests us new ideas on origin and organogeneses of shoots.

Thirdly, fasciation of Drosera may be another interesting phenomenon in tissue culture. Fasciation may be caused by mycoplasma or a recessive single gene or malformation. Induction and maintenance of fasciation by specific culture media may build up new breeding lines. These phenomena suggest us new ideas on origin and organogeneses of shoots.

Tissue-cultured shoot primordia were induced in Utricularia to analyze relationships of their underdeveloped organs, very peculiar organization of its vegetative organs that is quite different from those of other flowering plants; each of the vegetative structures in Utricularia can grow continuously and transform into any of the other vegetative structures and adventitious buds can appear on all of these vegetative structures. Since these differentiations can be correlated with differences in water qualities in habitats, Utricularia can be cultured in a closed, well-controlled microenvironment in vitro to study the relationship between organogenesis and specific chemical components of the medium. These data would also contribute to a satisfactory systematic treatment. NO₃^- (as in KNO₃) and BAP regulation system could control organogenesis in the tissue-cultured shoot primordia of Utricularia praelonga. Determination from the tissue cultured shoot primordia to the meristemoids may be triggered and controlled not by phytohormone but by the nitrogen source and subsequently that from the meristemoids to further meristemoid development may be promoted by phytohormone.

On the other hand, effects of macro-components and sucrose in the medium were studied on in vitro red-color pigmentation in Dionaea muscipula and Drosera spatulata. Dionaea and Drosera spatulata grow commonly in relatively closed ecosystem where the soil is poor in nutrient substances, wet and acid. A great question had remained for a long time why: why do the vegetative structures in Dionaea, Drosera (and many other carnivorous plants) have different colors in different natural habitats, and is this significant? There are reddish plants, greenish plants and intermediate plants. However, if they are cultivated in pots, they often change color in leaf. Moreover, if they are fed with certain nitrogen-concentrated fertilizers, they also change color in leaf and sometimes die.

Modified 1/2 MS media with less or no macro-element and with more sucrose induced red-color pigmentation in the inner surface of trap lobe in Dionaea muscipula and in the glandular hair in Drosera spatulata and furthermore in the whole leaves of the both species after four months culture. However, they made plant growth worse. In contrast, 1/2 MS media with more to complete macroelements promoted deeper green colored in the whole plant bodies and larger growth and more proliferation in the both species. HPLC profiled anthocyanins in red colored Dionaea muscipula and Drosera spatulata grown in 1/2 MS medium with no macro-component and supplemented with 1.5% sucrose at pH 5.6:

1. Delphinidin 3-O-glucoside in Dionaea.

2. Cyanidin 3-O-glucoside (chrysanthemin) in Dionaea.

3. Cyanidin 3,5-di-O-glucoside (cyanin) in Drosera spatulata.

4. Cyanidin 3-O-galactoside in Drosera spatulata.

5. Cyanidin 3-O-glucoside in Drosera spatulata.

6. Pelargonidin 3-O-galactoside in Drosera spatulata.

7. Pelargonidin 3-O-glucoside (callistephin) in Drosera spatulata.

Delphinidin 3-O-glucoside was reported in Dionaea by us for the first time, while the other one was already known in the species. All of the anthocyanins found here in Drosera spatulata have already been reported in other species of the genus. The anthocyanin pigmentation in the two species may be biosensitive to nitrogen uptake.