Anatomy of the Dicotyledons.
About: This article is published in American Midland Naturalist.The article was published on 1950-11-01. It has received 2511 citations till now.
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TL;DR: The developmental anatomy of Mirabilis jalapa was investigated during the first 90 days of growth, and differentiation of the PTM and the mode of secondary thickening is similar in plants exposed to short and long photoperiods, but some differences were observed.
Abstract: A B S T RA C T The developmental anatomy of Mirabilis jalapa was investigated during the first 90 days of growth. The primary thickening meristem (PTM) initially differentiates in the pericycle at the top of the cotyledonary node 18 days after germination, then basipetally in the pericycle through the hypocotyl. The PTM differentiates acropetally into the stem and in the pericycle of the primary root, commencing 22 days after germination. Endodermis is easily identifiable in hypocotyls as well as in primary roots because of Casparian thickenings in its cells. It has not been definitely identified in stems. There are three rings of primary vascular bundles in the stem. The PTM differentiates as segments of cambium in a layer of cells (probably in the pericycle) on an arc between vascular bundles of the outer bundle ring. Later, arcs of PTM differentiate externally to the phloem of each bundle. Each arc forms a connection between original segments of PTM lying on either side of each vascular bundle. Thus, the PTM becomes a continuous cylinder. The PTM differentiates in the pericycle outside vascular tissue in the hypocotyl and root. Differentiation of the PTM and the mode of secondary thickening is similar in plants exposed to short (8-hr) and to long (18-hr) photoperiods, but some differences were observed. The PTM differentiates closer to the stem apex in all plants over 18 days of age growing vegetatively under long photoperiods. That is, the diffuse lateral meristem, in whose cells the PTM differentiates in young internodes, is shorter in nearly all investigated plants growing in long photoperiods. The hypocotyl and base of the primary root of 40-dayold plants in short photoperiods were more enlarged than those of the same age plants in long photoperiods; but, at the end of 64 days, the hypocotyl and primary root base were larger in plants growing under short photoperiods. Thirty-four days after seed germination, flower initiation occurs in plants exposed to short photoperiods. One hundred fifty days after seed germination, flowers differentiate on plants exposed to long photoperiods.
24 citations
TL;DR: Ipomoea hederifolia stems increase in thickness using a combination of different types of c Cambial variant, such as the discontinuous concentric rings of cambia, the development of included phloem, the reverse orientation of discontinuous cambial segments, the internal phloems, the formation of secondary xylem andphloem from the internal cambium, and differentiation of cork in the pith.
24 citations
Cites background from "Anatomy of the Dicotyledons."
...Thus, fibriform vessel elements, which are common in Convolvulaceae and other lianas, can form a subsidiary conductive system with a degree of conductive safety virtually as high as that provided by tracheids (Ayensu & Stern, 1964; Carlquist, 1991: 151)....
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...The stem and wood anatomy of Convolvulaceae has been studied by different workers, with the most important contributions being those of D’Almeida & Patil (1945, 1946), Metcalfe & Chalk (1950), Mennega (1969), Pant & Bhatnagar (1975), McDonald (1981), Lowell & Lucansky (1986), Carlquist & Hanson (1991), and McDonald (1992)....
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...Radial secondary growth and formation of successive cambia and their products in Ipomoea hederifolia L. (Convolvulaceae) KISHORE S. RAJPUT*, VINAY M. RAOLE and DHARA GANDHI...
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...…anatomy of Convolvulaceae has been studied by different workers, with the most important contributions being those of D’Almeida & Patil (1945, 1946), Metcalfe & Chalk (1950), Mennega (1969), Pant & Bhatnagar (1975), McDonald (1981), Lowell & Lucansky (1986), Carlquist & Hanson (1991), and McDonald…...
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...Successive supernumerary cambia are common in woody species of Ipomoea, regardless of their growth habit (Metcalfe & Chalk, 1950: 961; McDonald, 1981; Lowell & Lucansky, 1986: 393, 1990: 243)....
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TL;DR: Phytoliths in the silt size range of the swamp sediment were isolated and quantified, and it was found that the forms with a small surface area to volume ratio survived in the sediment.
Abstract: Opal phytoliths in the leaves of 10 native species growing in and around a swamp were isolated and quantified, and shape and surface detail examined with a scanning electron microscope (SEM). The amount of plant opal in the leaves ranged from 0.10 to 2.45% by dry weight, and phytolith forms most commonly found were spheres, rods and sheets. Phytoliths in the silt size range of the swamp sediment were isolated by a simple fractionation technique. It was found that the forms with a small surface area to volume ratio survived in the sediment.
24 citations
TL;DR: A molecular phylogenetic analysis of the newly circumscribed and expanded tribe Poranthereae (Phyllanthaceae) is presented, supporting the recognition of Andrachne and Leptopus as distinct genera.
Abstract: Novel insights into the evolutionary history of a taxonomically complex tropical plant group were gained in this study using DNA sequence data. A molecular phylogenetic analysis of the newly circumscribed and expanded tribe Poranthereae (Phyllanthaceae) is presented. Sampling included 97 accessions for 63 of c. 120 species. Largely congruent results have been obtained from nuclear ribosomal ITS and plastid matK sequences. These analyses support the recognition of Andrachne and Leptopus as distinct genera. The deceptively similar Andrachne section Phyllanthopsis, Andrachne ovalis, and Leptopus decaisnei are separate lineages to be segregated. Zimmermannia and Zimmermanniopsis are embedded in Meineckia; Oreoporanthera is embedded in Poranthera; and Archileptopus is embedded in Leptopus. Andrachne section Pseudophyllanthus is polyphyletic, the two Madagascan endemics emerging as a sister clade to Meineckia. The noncontiguous distributions of Andrachne sensu lato and Leptopus sensu lato were found to be the result of separate evolutionary histories of morphologically similar clades, whereas Andrachne sensu stricto and Meineckia remain geographically disjunct. Actephila and Leptopus are sisters with a sympatric distribution in humid Asia. Presence of petals appears to be plesiomorphic for the tribe. Petals are reduced in Actephila and Oreoporanthera and lost in the Meineckia clade. Poranthereae.
23 citations
TL;DR: Anatomical evidence suggests that the segregation as distinct genera of Rea, Phoenicoseris, andHesperoseris is probably not justified, and that they are better treated as subgenera of Dendroseris.
Abstract: Anatomical study of the genusDendroseris (Compositae: Cichorieae), endemic to the Juan Fernandez Islands, was undertaken to determine if segregate genera were valid. Other questions include the significance of pith bundles and of receptacular bristles, and whether the ancestors of these peculiar rosette trees and shrubs were woody or herbaceous. Anatomical evidence, when added to that from gross morphology, suggests that the segregation as distinct genera ofRea, Phoenicoseris, andHesperoseris is probably not justified, and that they are better treated as subgenera ofDendroseris. Differences in pollen morphology, floral trichomes, achene and leaf anatomy provide good species characteristics. These all appear, respectively, as variations on a basic plan, andDendroseris can be envisaged as derived from a common stock in the Juan Fernandez Islands. The genus is not particularly primitive within the family or tribe. The presence of additional bundles in the flowers ofD. litoralis may be interpreted as related to gigantism. The separate corolla lobes inD. gigantea probably do not represent a vestige of an actinomorphic condition. Pith bundles inDendroseris may have been present in ancestors; in any case, they seem likely to have increased in prominence with increase in stem diameter. Available evidence seems to favor the interpretation of growth forms inDendroseris as derived from an herbaceous ancestry.
23 citations