HARN. Chang Yawl (Chonnam U. Kwangju, Korea): Siudies on the dimorpism of the Perisicaria senticosa Nakai-Kor. jour. Bot. 3(1) 16-25 During his researches regarding the morphological and physiological properties of Polygonaceae, the author has found that the species, Persicaria senticosa, aiso besides the heterostylous plants of Polygonum family, Fagopyrum esculentum, and Persicaria japonica which was recently verified by the author as dimorphic, shows the typical floral structure of heterostylism, the description of which is not found in taxonomical works.
Further research on this species have revealed that this plant, despite pessessing characteristic structulal dimorphism, does not exhibit even the slight signs of heterostylcus properties physiologically. This is a deviation from the usual behavior of normal heterostylous plants.
What is interesting is the fact that the physiological behavior of this speeies is quite contrary to that of P. japonica which is considered to be the most highly speciaiized dimorphic plant.
Thus it Is assumed that if some species of this family had taken a heterostylic form in its course of development from autogamy to allogamy, P. seoticosa would be the least differentiated type of dimorphic forms among the three heterostylous plants, including buckwheat, of this family.
The results obtained in this experiment are summarized as follows:
1) P. senticosa has two forms of flower, one, long style-short stamened; the other, short style-long stamened. Not only conspicuous is this primary difference, but the secondary difference, such as pollen grain size, is noticeable between long and short styled individuals, thus expressing structurally the definite trait of a dimorphic plant.
2) Structural alteration of floral parts towards dimorphism has preceeded far less in comparison with those of the P. japonica and F. esculentum.
3) Elaborate studies on fertility reveal that this species dose not show the slighbest sign of the physiological chararteristics of dimorphic plants. In other words, regardless of the modes of combinations, legitimate and illegitimate, fertilization and fruit setting flourish unimpaired.
4) Growth of pollen tubes apparently parallels the results in the fertility, tubes reaching ovary approximately 30 minutes after pollination both in legitimate and illegitimate combinations. Pollen tube penetration appears to be comparatively rapid.
5) A slight differenre in the growth of pollen tube seems to exist between legitimate and illegitimate combinations, legitimate union giving slightly faster tube penetration.
6) In the present experiment it was clarified that P. senticosa, known to possess one form of flower in taxonomy, is in reality dimorphic plant having two of flowers. Although this species if definitely heterostylous in floral structure, physiological evidence and pollen tube behavior show that the differentiation of this plant toward the dimorphism has apparently proceeded slightly except for some parts of floral organ. In ordinary heterostylous plants it is a matter of common occurrence that when iilegitimately combined, there is poor or no fertility, Contrary to the universal propety of heterostylous plants, no difference is oberved in the fertility and pollen tube gowth between the legutumate and illegitimate combinations in the case of P. somkiosa. Compared to the P. japonica and F. esculentum, whichare supposed to have undergone high degree of dimorphic differentiation, it is an unavoidable conclusion that P. senticos has not yet developed as a heterostyle plant except for some of its floral parts. If P. japonica is assumed to be the most diffentiated type of heterostylous plant, thenthe P. senticosa would be regarded as the primitive, retaining still the self-fertile nature so common to the Polygonun genus. In nature, however, this plant has a better chance to be pollinated legitimately owing to the two forms of flowers than to be pollinated illegitimately.
The author is indebted to Dong Chul, Kim as well as other members of the Depatment of Plant Breeding and Genetics of Chonnam National University for their efforts in carrying out the laborious experiments during the course of the present studies.
|