Cuticular variation in Kalanchoe and Datura
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"The epidermal characters, if properly interpreted, are being regarded as important taxonomic tools. They should not be dissociated from supplementing the morphological features which have so long been used in the taxonomic and phylogenetic interpretations. Since the development of the technique by Sinclair and Dunn (1961), consistent attempts have been made and still are being made to find the values of the cuticular features in the systematics. Their process has made it possible to handle such investigations with ease and dexterity, and with very encouraging results, which have been used to explain some rather basic differences between monocotyledons and dicotyledons by Dunn, Sharma, and Campbell (1965). Cuticular features such as stomatai frequency, stomatai index, stomatai complex, trichomes, and others are helpful in understanding relationships which could not be explained otherwise. Fritsch (1903) believed that the characteristic structure of the stomatai apparatus in many plants is undoubtedly due to an inherent property in the plant and he considered them to be of great importance in the characterization of some orders..." Since their mere occurrence and constancy are genetically controlled, it should be helpful to utilize these features of the cuticle as taxonomic tools, which may be used in phylogenetic comparisons." If constancy of various characters can be accepted at various levels of a taxon - some are applicable at species level, while others are useful at the generic or familial level. It is, therefore, imperative that environmental variations, as affecting the cuticular features, should be studied critically. The understanding of the degree of modification would affect the value one could place on each trait, regarding reliability. It is with this in mind, that two different plants - Kalanchoe fedschenkoi and species of the genus Datura, belonging to families Crassulaceae and Solanaceae respectively, were chosen for the present study on the effects of different environmental conditions in the greenhouses. There are certain cuticular characters which are affected by environment while there are others which are 'significantly' constant. The results obtained from such studies supplement but definitely do not supplant the reliability and importance of other genetically controlled features including the classical morphological characters. An alliance of the morphological, anatomical, and cuticular characters may help resolve some of the phylogenetic problems in paleobotany and living plant material. Stebbins (1961) rightly remarks that another point "which makes the study of the stomatai complexes a desirable tool in taxonomic research is that genera and even families show great constancy for their possession of a particular complex, yet there is considerable variability from one higher taxon to another. Thus, at the level where classical methods of cytology and genetics cannot be applied, this study of stomatai complexes should help us to understand true evolutionary relationships of monocotyledons". Accordingly, this study deals with the taxonomic value of the cuticular features of flowering plants as seen in the cuticular imprints. It also embraces a discussion of these cuticular features which are useful in taxonomy, and of the variations which are exhibited by some of these under different environmental conditions. Finally in the words of Stace (1965), "a soundly based theory of cuticular patterns can be put to a good number of uses besides the obvious applications in identification, taxonomic research, and phylogenetic investigations. These include peat stratigraphy, pharmacological analyses and animal foodstuff research." In the present study, morphological features have been studied along with the epidermal characters while the plants used were subjected to different environmental conditions. A comparison is also presented for the species of Datura, which are considered as authentic material. These studies are based on the Blakeslee seed collections which were successfully germinated, as well as original field collections from within the natural distributional range of several species. It is hoped, then, that the present study will help to understand taxonomic and eventually phylogenetic relations that exist in various groups of plants, both living and fossil."--Introduction.
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