Proc. Indian Aead. Set., Vol. 85 B, No. 5, 1977, pp. 319-326. Phyllody disease of Raphanus sativus L. and variation in the epidermal structure S. MISRA AND M. G. GUPTA Department of Botany, University of Rajasthan, Jaipur 202004 MS received 6 July 1976 ABSTRACT A phyllody disease of suspected MLO etiology was noticed on a plant of Raphanus sativus in the fields of Sanganer, Jaipur, nearly 3 years ago; and later in other localities in and around Jaipur. A study of the various features of epidermal structure in the normal as well as diseased material has shown that apart from tee stomatal types, which usually remain unchanged, the epidermal structure undergoes considerable change from normal to the diseased condition. The sepal, petal and carpel of of diseased flowers show phyllody and the stamen becomes sepaloid. And that the degree of phyllody in these organs increases in the direction of carpels. 1. INTRODUCTION ON a botanical trip to Sanganer, Jaipur, nearly 3 years back we came across a plant of radish which was severely affected by a disease usually referred to as phyllody. In the following years the disease was observed again but in some other localities within and round about Jaipur. As a teratological phenomenon, however, the phyllody in case of radish was recorded about a century ago l-a and was described by the authors under anomalies like phyllody of the corolla, phyllody of the entire flower, and phyllody of the ovules. Recently Hulbary et al. 4 reported prolification in the flowers of radish and considered it as an anomaly of unknown causal mechanism. During the past 8 or 9 years diseases like Sesamum phyllody,5 phyllody of pea, e leucerne witches'-broom, 7 etc., in which floral anomalies of the above types as well as witches'-brooms are produced as characteristic symptoms have been ascribed to infections by certain microorganisms resembling those 319 B7--May 77 320 S. MISRA AND M. G. GUPTA of the class mollicutes.8,9 This interested us in taking up the material of radish for morpho- and histopathological studies. The present contri- bution concerns a part of this study and describes our observations on the epide~-mal structures in the normal as well as diseased material and also explores the possibility of using it for the purpose of assessing the real nature of the various transformations in the so called phyllodic flowers. As far as known to us, studies of this type have not been done so far. However, in case of the phyllody disease of Sesamum mulayanum, recently, Kavathekar et al. 1° have attempted to bring out certain features of epidermal structure of the transformed in comparison to that of the normal floral organs. 2. MATERIALS AND METHODS The materials, both normal as well as diseased, were collected during the third week of January 1973 and were fixed in acetic-alcohol. They were washed and then preserved in 70~ alcohol. A portion of the diseased plant was prepared into a type herbarium sheet and deposited in the Rajasthan University Botanic Herbarium under No. RUBL 11839. The preserved materials were used for making preparations of epidermal peels from various parts of the entirely phyUodic and normal flowers as well as normal and diseased leaves. A peel was usually taken off with the help of forceps after putting the plant part under water. It ~as stained in aqueous safranin, washed thoroughly with water, mounted in dilute solu- tion of glycerine and thereafter the coverglass was sealed with cutex nail- polish. Since peeling was not possible in normal petal and stamen whole mounts were prepared for the study of these organs. The stomatal counts were done under high power of the microscope ~45 × objective and 15 × eye piece) and by taking the microscopic field as the unit area. Later the readings were converted to the number per mm ~. For the comparison of total epidermal pattern camera-lucida drawings were made at uniform magnification. 3. OBSERVATIONS Observations of diseased plants in the field have made it clear that symp- toms like colour breaking in the corolla, virescence, phyllody and proliti- cation in flowers, are characteristic of the phyllody disease of radish (Plato I, figures A, B, C, D). And that their occurrence usually depends on the stage at which the plant has been infected and also on the severity of the infection. GROSS MORPHOLOGY OF THE EPIDERMIS.--The leaf, in both the normal as well as diseased material, is amphistomatic. Its epidermis on either side PHYLLODY DISEASE OF Raphanus sativus L. 321 (Explanations given in p. 326) 322 S. Mtsag ANO M. G. GUPTA is composed of cells with irregular orientation and sinuate outline in the normal, and with mostly longitudinal orientation and less sinuate to almost smooth outline in the diseased material (figures 1, 2 and 7, 8). The sepal also is amphistomatic in both normal as well as diseased conditions. Its epidermis on either side is usually made up of cells longi- tudinally elongated and with smooth outline, except in case of the abaxial surface of the diseased sepal where the cells are slightly sinuate in outline (figures 3, 4 and 9, 10). The petal in the normal condition is astomatic and its epidermis on either surface is made up of highly characteristic polygonal ceils. In the diseased condition the petal is amphistomatic and its epidermis on either side is composed of cells which are mostly elongated longitudinally and with a smooth outline (figures 5 and 11, 12). The stamen in the normal condition has a typical anther-filament type structure and is astomatic. In the diseased condition it is laminar and amphistomatic and with the epidermis on either surface consisting of cells elongated and with shghtly sinuate outline which is more conspicuous in the case of abaxial epidermis (figures 13, 14). The carpel (one lateral half of the gynoecium) in the normal condition is hypostomatic and its epidermis on the abaxial side is composed of cells small and mostly elongated. In the diseased condition it is amphistomatic and with the epidermis on either side composed of ceils vertically elongated, and with slightly sinuate outline at least in case of the abaxial epidermis (figures 6 and 15, 16). STOMATAL TYPES.~With regard to the occurrence of the various stomatal types there appears to be hardly any difference between the normal and diseased materials. In general the stomata of the anisocytic type are the most common (Plate II, figures 17, 21, 22). Next in abundance are those of the anomocytic type. Besides, there are stomata of several unusual types, common among these are: (i) a combination of 2-3 stomata with one subsi- diary cell common (figure 2); (ii) contiguous or paired stomata (figures 4, 12, 15); ('tii) stomata with one or both the guard ceils degenerating (Plate II, figures 18, I9); and (iv) abortive stomata, with the guard cells undergoing arrest of development at an early stage (figure 4). While stomata of all these types are found to occur on almost all the stomatic surfaces, those of the contiguous type being abundant especially S. Misra and M. G. Gupta Proc. Indian Acad. SeL, Plate I Vol. 85 B, No. 5, 1977, pp. 319-326 Figures A, B, C, D. Habit photographs of normal and diseased twigs. A--Diseased twig with less affected flowers; B--Diseased twig with flowers showing increasing phyllody in acropetal direction. C and D--Nermal twigs with flowers and fruits respectively. (.facing page 322) S. Misra and M. G. Gupta Proc. Indian Acad. Sci., Plate H Vol. 85 B, No. 5, 1977, pp. 319-326 , ~" ~i¸ F--- I ~..~I ' ,. o.. 22 Figures 17 to 22. Comparison of stomatal types; 17. Stomata healthy, on abaxial epidermis of normal leaf; 18. Stomata with degeneration of one guard cell, on abaxial epidermis of diseased leaf; 19. Same, later stage of degeneration, on adaxialepidermis of diseased leaf; 20. Stomata with distended guard cells and deformed openings, on abaxial epidermis of diseased sepal; 21. Stomata, on abaxial epidermis of maturing normal carpel; 22. Single stornatal apparatus of 21 magnified. (facing page 323) PHYLLODY DISEASE OF Raphanus sativus L. 323 in the case of abaxial epidermis of the normal sepal (figure 4) and adaxial epidermis of the diseased petal (figure 12) as well as carpel (figure 15). The stomata of the third and fourth types which together come under the category of degenerating stomata are more frequent on the diseased in comparison to the normal material. Of the category of unusual types of stomata there is one more type which is uncommon. This type (5) is recognized by an excessive distention in the guard cells and characteristic deformity of the stomatal opening (Plate II, figure 20). It is found to occur on the abaxial surface of the diseased sepal only and is probably confined to it. The stomata of the 3, 4 and 5 types invariably degenerate, hence may be found at different stages of degeneration. The dimensions of the well developed stomata range between 14.6/~ x 14.6/z and 21 "9/~ x 17.0/z in the normal, and between 18-3/z x 14.6/z and 25.5/z x 29.0/~ in the diseased material. Based on these figures the length/width ratio of the stomata comes to 1 or more than 1 and never tess than 1 in the normal, but ranges between more than 1 and less than 1 in the case of diseased material. FREQUENCY OF STOMATA.--The frequency of stomata calculated in res- pect of stomatic surfaces of the various organs under normal as well as diseased conditions is recorded in table 1.