Flowers from 15 species of the genus Dalea (Leguminosae) were cleared and stained. Complete isolation of the xylem of the gynoecium, androecium and corolla from the pedicel xylem was found except in two species. The most obvious feature was the  discontinuity plate  formed by the merger of the xylem of the gynoecial traces in a characteristic mass of tracheoidal cells near the base of the flower. Variation in the floral vascular pattern appears to have taxonomic implications

Brady, Eugene R.

Lersten, Nels R.

Wemple, Don K.

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 71 Annual Issue Article 8 1965 Floral Vasculature as a Potential Taxonomic Character in Dalea (Leguminosae) Eugene R. Brady Iowa State University Don K. Wemple Iowa State University Nels R. Lersten Iowa State University Let us know how access to this document benefits you Copyright ©1964 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Brady, Eugene R.; Wemple, Don K.; and Lersten, Nels R. (1965) "Floral Vasculature as a Potential Taxonomic Character in Dalea (Leguminosae)," Proceedings of the Iowa Academy of Science, 71(1), 46-51. Available at: https://scholarworks.uni.edu/pias/vol71/iss1/8 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. Floral Vasculature as a Potential Taxonomic Character in Daleo (Leguminosae)1 EuGENE R. BRADY, DoN K. WEMPLE, AND NELS R. LERSTEN2 Abstract. Flowers from 15 species of the genus Dalea ( Leguminosae) were cleared and stained. Complete isolation of the xylem of the gynoecium, androecium and corolla from the pedicel xylem was found except in two species. The most obvious feature was the "discontinuity plate" formed by the merger of the xylem of the gynoecial traces in a characteristic mass of tracheoidal cells near the base of the flower. Variation in the floral vascular pattern appears to have taxonomic implications. The tribe Psoraleae of the Leguminosae has received a lucid circumscription by Isely (I). He recognized six North Ameri-can genera: Psoralea (over IOO spp.), Amorpha (perhaps 20 spp.), Parryella ( 2 spp.), Eysenhardtia (IO spp.), Dalea (about 150 spp.) and Petalostemon ( 35 spp.). Barneby ( 2) has since delimited another genus, Errazurizia ( 4 spp.). The most de-finive characters of the tribe are the conspicuous glandular-dotted foliage, and the I-seeded indehiscent pods. Except for some species of Psoralea, the tribe is confined to North and South America, with its center of distribution presum-ably in the southwestern United States and northern Mexico. A limited number of chromosome counts have been made in four of the genera: in Dalea and Petalostemon x = 7, in Amorpha x = 10, in Psoralea x = IO or 11. Counts made since lsely's synopsis are in agreement with the previous findings. Polyploidy has been found only in Amorpha. Isely (I ) postulated three distinct lines in the Psoraleae based on corolla differences and supported by chromosome numbers. Of the seven genera only Psoralea possesses, as a constant char-acter, a papilionoid corolla with petals inserted below the sta-mens in a single whorl. Psoralea, by itself, constitutes one distinct line. Eysenhardtia has five petals that are attached basally, but they are aH similar in appearance and scarcely papilionoid. Amorpha possesses only a standard, and Parryella is devoid of a corolla. Errazurizia, which seems allied to the three preceding genera, lacks constancy in petal number. One species possesses 1 Journal Papn No. J-4869 of the Iowa Agricultural and Home Economics Experi-ment Station, Ames. Project No. 1073. The facilities of the Iowa State Herbarium, supported by the Industrial Science Research Institute, were used. :! Deparhnent of Botany and Plant Pathology, Iowa State University, Ames, Iowa. These studies were initiated while the senior author was a National Science Foundation Research Participant during tlw summer of 1963. The .second author is a National Science Foundation Graduate Fellow. We are indebted to Professor Duane Isely for the initial suggestion of this project and for encouragement and advice during its progress. 46 1Brady et al.: Floral Vasculature as a Potential Taxonomic Character in Dalea (LPublished by UNI ScholarWorks, 19641964] FLORAL VASCULATURE IN DALEA 47 five petals, while another has only one. In the latter species some flowers lack a corolla ( 2). A third line is composed of Dalea and Petalostemon. Flowers of Dalea have a standard, wings, and keel. The standard in-variably is inserted on the hypanthium, but the insertion of wings and keel varies among species. In some species all petals are inserted on the hypanthium. In other species the wings and keel are inserted laterally on the androecial tube; in these the insertion is at some intermediate point between the base and the apex of the tube. When the insertion is close to the apex, the number of stamens is sometimes reduced from the normal ten to eight or even to six in some individuals. Petalostemon differs from Dalea in having only five stamens and in the fact that the petals other than the standard are inserted at the apex of the androecial tube alternating with the stamen filaments. Within the Papilionoideae there is probably no other tribe that exhibits as much variation in the corolla as does the Psora-leae. A comparative survey of certain aspects of floral morphology in the entire tribe has been initiated. This report is concerned with a preliminary survey of selected species of Daloo. MATERIALS AND METHODS Flowers of 15 species of Dalea were examined. Material was taken from herbarium specimens. In addition, fresh flowers in all stages of development were collected from living plants of three species. The species sh1died were not chosen at random but were selected to sample postulated subgeneric groups, e.g. Rydberg's ( 3) segregate genera: Psorodendron, Psorothamnus, Parosela and Thornbera. The specimens, all from ISC, are as follows: Dalea albiflora Gray: Arizona, Chiricahua Mountains, M. P. Somes 1476. D. enneandra Nutt.: Iowa, Plymouth County, R. F. Thorne 14675. D. filiformis Gray: Arizona, Rincon Mountains, J.C. Blumer 3343. D. formosa Torr.: New Mexico, Bernalillo County, A. L. Kam-merer 17. D. fremontii Torr.: (mature fruit) Calif., Inyo County, AI:exander and Kellogg 5305. : Calif., San Bernardino County, M. Beal 234. D. leporina ( Ait.) Kearney & Peebles: Minnesota, Yellow Med-icine County, L. H. Pammel. : Guatemala, Lake Retana, Goodman & Melhus 3703. D. mollis Benth.: Calif., San Bernardino County, Isely & Bragon-ier 7244. D. nana Torr.: Texas, Jones County, N. C. Henderson 62-869. 2Proceedings of the Iowa Academy of Science, Vol. 71 [1964], No. 1, Art. 8https://scholarworks.uni.edu/pias/vol71/iss1/848 IOWA ACADEMY OF SCIENCE [Vol. 71 D. polyadenia Torr. ex Wats.: Calif., San Bernardino County, M. Beal 597. D. polygonoides Gray: Arizona, Rincon Mountains, J. C. Blumer 3584. D. schottii Torr.: Calif., Riverside County, Y. W. Winbald. D. scoparia Gray: New Mexico, Valencia County, Hitchcock & Stanford 6765. The most accurate and rapid way to follow the vascular bundles of a flower is by clearing and preferentially staining its vascular system. Best results were obtained by the following method ( 4). Place dried flowers in 5% aqueous sodium hydroxide for several days or until colorless. Fresh flowers must first be killed in 95% alcohol or formalin-acetic acid-alcohol (FAA) and subsequently rinsed in distilled water before the sodium hydroxide treatment. The time in sodium hydroxide can be shortened by placing the specimens in a 37°C. oven in stacked Syracuse watch glasses, thus minimizing evaporation. Remove the sodium hydroxide with three changes of distilled water and transfer to a chl'oral hydrate solution ( 250 mg./100 ml. water). Visual inspection will determine when the clearing action is completed. A few days are usually sufficient. Remove all traces of chloral hydrate with three changes of distilled water. With fragile material it is advisable to first go through two or three progressively more dilute solutions of chloral hydrate. Dehydrate in steps of 10, 25, 50, 75, 95%, and two changes of absolute alcohol. Transfer to equal parts absolute alcohol : xylene. Fifteen minutes should be allowed for each step with more time allowed for thick specimens. Stain in 1% safranin in equal parts absolute alcohol : xylene. A staining duration of from five to 15 minutes is usually adequate. Destain to the desired intensity in absolute alcohol : xylene. Finally, transfer to xylene. Change twice to remove bits of precipitated safranin. If the color seems too intense, the specimen can be returned to the alcohol : xylene for further destaining. The mounting medium is Piccolyte. The cover glass should not be pressed down or weighted, because this may destroy the vascular continuity of the now brittle specimen. As the Piccolyte solvent evaporates, more Piccolyte can be added at the side of the cover glass and capillary action will fill the mounting area with the resin. Whole mount clearings were supplemented by serial sections of flowers cut at 10 microns. Craf III was the preferred fixative and a standard safranin-fast green schedule was used ( 5). 3Brady et al.: Floral Vasculature as a Potential Taxonomic Character in Dalea (LPublished by UNI ScholarWorks, 19641964] FLORAL VASCULATURE IN DALEA 49 OBSERVATIONS The survey of Dalea revealed that the xylem of the vascular bundles of the androecial tube and the gynoecium is not con-nected. A xylem discontinuity also exists between the an-droecial tube, the gynoecium and the pedicel. There is, however, continuity of phloem across the gaps. The most obvious feature is the "discontinuity plat e" formed by the merger of the xylem of the gynoecial traces in a characteristic mass of n·acheoidal cells. Figures 1 and 2 show these vascular peculiarities. These discontinuities are not artifacts. We have verified them in micro-tome sections, and they can be seen quite easily with a hand lens in fresh flowers cut in median longitudinal section with a razor blade. Figures 1, 2. Enlargements of the pedicel and basal portion of cleared flowers. Figure 1. Dal,ea leporina Figure 2. Dal,ea au.rea Specific differences in floral morphology and vasculature are as follows. In Dalea fremontii the petals are inserted on the hypanthium free from the androecial tube (Fig. 5) . The single trace of each petal is connected to the trace of the adjacent calyx lobe; therefore, the corolla vasculature is continuous into the pedicel. The same arrangement occurs in D. schottii, which also has the petals inserted on the hypanthium. Of the dozen flowers of these two species examined, in only one flower ( D. schottii) was a stamen bundle found that had xytem that was continuous with the pedicel xylem, and this connection was a tenuous one. In the rest of the species examined, representatives of the 4Proceedings of the Iowa Academy of Science, Vol. 71 [1964], No. 1, Art. 8https://scholarworks.uni.edu/pias/vol71/iss1/850 IOWA ACADEMY OF SCIENCE [Vol. 71 [ \ 0 v / \, . ,~ .. /' ',, ___ ( p ,) Imm , 3. Figures 3-5. Camera lucida drawings of the basal portions of flowers of species of Dalea. Figure 3. Dalea leporina. The same flower as Figure 1. Figure 4. Dalea aw-ea. The sam e flower as Figure 2. Figure 5. Dalea fremootii A, petal and stamen traces of the androecial tube; B, bract trace; C, calyx trace; D , dorsal carpel bundle; P, petal trace; S, standard trace; V, ventral carpel bundles. sections of Dalea in which wings and keel are inserted on the androecial tube, the petal traces are discontinuous. The standard remains attached to the hypanthium and in some species retains a continuous xylem connection with the pedicel bundles (Figs. 4, 5). The staminal traces are continuous from the free portion of the filaments down through the major part of the androecial tube. In the lowermost part of the tube, near the periphery of the discontinuity plate, the xylem of the traces ends abruptly in parenchyma tissue (Figs. 2-6). A novel discontinuity is found in the gynoecial vasculature. The dorsal and the two ventral bundles of the carpel merge just below the base of the carpel and the xylem terminates as a discontinuity plate. Although varying in size among species, a recognizable plate was found in all species examined. Figures 3-5 show some of the kinds of discontinuity plates observed. In Dalea frerrwntii (Fig. 5) and D. schottii, a related species, this structure is relatively massive. Dalea leporina, on the other hand, has a relatively small, weakly developed plate (Figs. 1, 3). Dalea aurea possesses a plate of intermediate size. This latter type was most frequently observed among the species studied. Evidence suggests that the discontinuity plate is constant within a species. For example, entire inflorescences consisting of many flowers were cleared, and no variation was found in the plate among the individual flowers . In Dalea leporina, flowers from a specimen collected in Minnesota and from a specimen collected in Guatemala, were cleared and compared. The weak 5Brady et al.: Floral Vasculature as a Potential Taxonomic Character in Dalea (LPublished by UNI ScholarWorks, 19641964] FLORAL VASCULATURE IN DALEA 51 discontinuity plate characteristic of this species (Figs. 1, 3) was identical in flowers from these widely separated areas. CONCLUSIONS The xylem discontinuities in the vasculature of the flowers described are clearly regular, recurrent features. A survey of the literature on floral vasculature is underway to determine if similar phenomena have been reported in other groups. The only previous reports we have seen relate to flowers of the Poly-gonaceae ( 6, 7). In this family floral vascular discontinuity seems to be the rule. If such discontinuities are of rare occurrence among Angio-sperms, their presence in a certain genus or tribe could be of considerable taxonomic value. Our studies are being extended to other genera of the Psoraleae. Literature Cited I. Isely, D. 1958. Iowa State Coll. Jour. Sci. 33:23-36. 2. Barneby, R. C. 1962. Leaf!. Western Bot. 9:23-36. 3. Rydberg, P.A. 1919-1920. N. Am. Fl. 24:1-136. 4. Lersten, N. R. 1963. Morphological and histogenetic studies on leaf and petal venation in Tiifolium. Unpub. Doctoral thesis, Univ. of Calif. Library, Berkeley. 5. Sass, J. E. 1958. Botanical microtechnique. 3rd ed. xi + 228 pp. Iowa State Univ. Press. Ames. 6. Vautier, S. 1949. Candollea 12:219-343. 7. Horton, J. A. 1963. Brittonia 15:177-202. Notes on Iowa Diatoms. VI. Frustular Aberrations in Surirella Ovalis1 RYAN w. DRUM2 Abstract. Two types of frustular aberrations in cultures of Surirella ovalis Breb. have been observed. The first is a "notch deformity" occurring in approximately 0.1% of the population. It is produced by mechanical distortion where the cells are crowded. This deformity is passed to daughter cells in each successive vegetative division. The second type is characterized by the presence of one or more aberrant raphe canals crossing the valve face in various directions. It occurred only in cultures exposed to continuous light for two weeks. Little or no cell division occurred during this period. The raphe canal aberrations, which occurred in about 0.01% of the exposed population, may have resulted from abortive cell divisions. They were not observed to continue in later transfers of the exposed populations to normal growth conditions. 1 This work was supported by Grant number WP-0221-03, from the Division of Water Supply and Pollution Control, Public Health Service •Department of Botany and Plant Pathology, Iowa State University, Ames, Iowa 6Proceedings of the Iowa Academy of Science, Vol. 71 [1964], No. 1, Art. 8https://scholarworks.uni.edu/pias/vol71/iss1/8

Floral Vasculature as a Potential Taxonomic Character in Dalea (Leguminosae)

Name not available

https://scholarworks.uni.edu/cgi/viewcontent.cgi?article=2175&context=pias

Floral Vasculature as a Potential Taxonomic Character in Dalea (Leguminosae)

Abstract

Similar works

Full text

Available Versions

University of Northern Iowa

Name not available