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 myrosin cells were characterized morphologically and compared to other idioblasts in the tissue, and changes in ultrastructure take place during development and light has a negative effect on the extent of cellular differentiation.
Abstract: The occurrence and distribution of myrosin cells and myrosinases has been followed in different organs during development of 7 species of the Brassicaceae. Using light and electron microscopy the myrosin cells were characterized morphologically and compared to other idioblasts in the tissue. Myrosin grains stain specifically with toluidine blue, methylene blue azur-II, lactophenol aniline blue and fuchsin. At the ultrastructural level myrosin grains were seen to contain proteins, and oleosomes occupy most of the myrosin cells at an early stage of development in young seedlings, together with precursors for mitochondria, plastids and microbodies. Changes in ultrastructure take place during development and light has a negative effect on the extent of cellular differentiation. Myrosin cells are generally found distributed in differentiated tissue, from the imbibition stage up to 192 h after germination. The relative area occupied by the myrosin cells has been calculated by morphometrical analyses an...
55 citations
TL;DR: This review article contributes in more understanding of most aspects of Calotropis procera procerabiology and extend the knowledge about its behavior.
Abstract: This review article contributes in more understanding of most aspects of
Calotropis procera
biology and extend our knowledge about its behavior.
Calotropis procera (Aiton) W.T (Asclepiadaceae) (Giant milkweed) is a xerophytic perennial shrub or small tree. It is native to tropical and subtropical Africa, Asia and common in the Middle East. It grows on a variety of soils, from fine to coarse texture, with varying degrees of salinity. The importance of C. procera in the functioning of ecosystems is reflected in its hosting of butterflies, while it also acts as a food plant for arthropods. In addition, it is used for medicinal purposes in many arid countries. Potential new uses of this species in semi-arid regions include the phytoremediation of soils contaminated with trace elements and the use of biomass as a source of renewable energy.
55 citations
TL;DR: The xylem/phloem ratio is an important factor in the interpretation of diptero-carp bark construction and similarities within the three groups of Bark Types in Dipterocarpaceae arise, therefore, from the dependence of periderm pattern, sloughing and fissure shape on the xyleM/phLoem ratio.
Abstract: Summary
The production of xylem and phloem sets up tangential stretching forces through the bark. In the living inner bark the resulting strains are mainly accommodated in Dipterocarpaceae by the formation of expansion tissue. The strain set up by a given annual girth increment decreases with increasing girth to a low steady amount at about 90 cm (3 ft) girth. Phloem formation in a mature tree only sets up small strains. These increase from zero at the cambium to a maximum at the surface. Many barks have more expansion tissue than this accounts for; the rest accommodates the strains set up by xylem formation. The tangential extent of the expansion tissue at a given distance from the cambium in any bark is in fact a measure of the ratio of the xylem and phloem growth rates. The three groups of Bark Types in Dipterocarpaceae with different amounts of expansion tissue (Whitmore, 1962a) are therefore groups with different xylem/ phloem ratios.
Phloem growth rate determines periderm pattern and sometimes sloughing rate too. Fissure shape is controlled by periderm pattern and sloughing rate. The xylem growth rate is similar in different groups of dipterocarps. Thus the xylem/phloem ratio is an inverse measure of the phloem growth rate which cannot be measured directly. There is therefore a correlation between the xylem/phloem ratio and periderm pattern, sloughing and fissure shape.
Similarities within the three groups of Bark Types in Dipterocarpaceae arise, therefore, from the dependence of periderm pattern, sloughing and fissure shape on the xylem/phloem ratio. Differences within the three groups arise from features, which are independent of the ratio: inter alia the phloem proliferation tissue, which probably varies phenotypically, and the sloughing mechanism.
It follows that the xylem/phloem ratio is an important factor in the interpretation of diptero-carp bark construction.
There is no evidence of growth periodicity in the barks examined. Calculations show that the phloem is often conducting for more than 1 year to an observed maximum of 11.4 years; this is in marked contrast with most reports for temperate phloems.
55 citations
TL;DR: Epidermal structure and ontogeny of stomata are described for ten species or varieties of Cruciferae, typically anisocytic, of the mesogenous trilabrate type.
55 citations
TL;DR: The earliest records of the modern Salicaceae are from North America with Populus section Abaso in the Late Palaeocene and Salix subgenus Salix in the early Eocene.
Abstract: Current evidence for early fossil Salicaceae is summarised. Most data come from Europe and North America where revisionary studies are in progress in several laboratories. The earliest records of the modern genera are from North America with Populus section Abaso in the Late Palaeocene and Salix subgenus Salix in the early Eocene. This evidence is based mainly on leaves but the presence of Populus is confirmed by a leafy shoot with attached fruiting raceme. The two genera first occur later in Europe with Populus in the uppermost Eocene and Salix in the Middle Oligocene. Members of both genera in both continents apparently occupied riparian habitats early in their history.
55 citations