Parenchyma Of Species Research Articles

Role of CLE41 Peptide in the Development of Root Storage Parenchyma in Species of the Genus Raphanus L.

CLE peptides (CLAVATA3/ENDOSPERM SURROUNDING REGION) are signal molecules or plant peptide hormones that play an important role in regulation of development of various meristems governing the expression of WOX (WUSCHEL-RELATED HOMEOBOX) genes. In particular, CLE peptides belonging to a small TDIF (Tracheary Element Differentiation Inhibitory Factor) group are responsible for the operation of gene WOX4 controlling the development of cambium and the conducting system. We looked into the role of CLE41 peptide from the TDIF group in the development of storage root in two species of the genus Raphanus: cultivated radish (Raphanus sativus var. radicula Pers.) that is a popular root crop with a storage root and its ancestor wild radish (Raphanus raphanistrum L.) where storage parenchyma of the root is poorly developed. It was shown that overexpression of gene RsCLE41 and plant treatment with exogenous peptide CLE41 influenced the development of cambium and xylem in the roots of R. sativus and R. raphanistrum and affected expression of the genes from different groups. One could say that peptide CLE41 activates expression of the genes whose homologues in arabidopsis play a key role in the maintenance of cambium (RsWOX4, RsWOX14, RsHAM4, and RsCYCD3). In the storage root of radish, peptide CLE41 activates proliferation of cambium cells reducing the amount of one of the xylem’s elements (lignified parenchyma). The obtained results point to an important role of CLE41 in the development of storage root in radish.

Wood functional anatomy of Chiococca alba Hitch. (Rubiaceae) from cerrado

The wood anatomy is able to evidence systematic and ecological aspects associated with the evolution and functionality of the secondary xylem. The present study was carried out using wood of Chiococca alba (Rubiaceae) from cerrado (savannah), to describe its anatomy and to verify if the hydraulic architecture of this species corroborates the theory that postulates the functional tendency that optimizes the transport efficiency associated with safety. The anatomical analysis followed the conventional protocols of wood anatomy. Different indexes of wood hydraulics quantification were calculated, such as solitary vessels index, vessel grouping, conductivity, vessel collapse, theoretical resistance to vessel implosion and mesomorphism. The structural characteristics described for C. alba are in agreement with the general anatomical descriptions for the Rubiaceae family that relate the presence of exclusively solitary vessels and small diameter, simple perforation plates, alternate intervessel pits, apotracheal parenchyma in species with non-septate fibers and narrow and heterogeneous rays. The calculated indexes showed that C. alba is a xerophyte species with great resistance to the collapse of the vessels during the transport of water, little vulnerability to embolism and relative efficiency in the transport when compared to other species of its subfamily (Cinchonoideae) in function of the typical low water availability of the savannah soil.

Wood functional anatomy of Chiococca alba Hitch. (Rubiaceae) from cerrado

The wood anatomy is able to evidence systematic and ecological aspects associated with the evolution and functionality of the secondary xylem. The present study was carried out using wood of Chiococca alba (Rubiaceae) from cerrado (savannah), to describe its anatomy and to verify if the hydraulic architecture of this species corroborates the theory that postulates the functional tendency that optimizes the transport efficiency associated with safety. The anatomical analysis followed the conventional protocols of wood anatomy. Different indexes of wood hydraulics quantification were calculated, such as solitary vessels index, vessel grouping, conductivity, vessel collapse, theoretical resistance to vessel implosion and mesomorphism. The structural characteristics described for C. alba are in agreement with the general anatomical descriptions for the Rubiaceae family that relate the presence of exclusively solitary vessels and small diameter, simple perforation plates, alternate intervessel pits, apotracheal parenchyma in species with non-septate fibers and narrow and heterogeneous rays. The calculated indexes showed that C. alba is a xerophyte species with great resistance to the collapse of the vessels during the transport of water, little vulnerability to embolism and relative efficiency in the transport when compared to other species of its subfamily (Cinchonoideae) in function of the typical low water availability of the savannah soil.

Non-lignified parenchyma in Cactaceae and Portulacaceae

This work describes the occurrence and distribution pattern of non-lignified parenchyma in species of Cactaceae and Portulacaceae, of which samples of roots and stems of six species of Cactaceae and four species of Portulacaceae were analysed. The first records of non-lignified parenchyma in Portulacaceae were obtained and, in the case of Cactaceae, an in-depth discussion is given on the characterization of this tissue by various authors, as well as new information on the occurrence and distribution pattern of the non-lignified parenchyma. The terminology used to characterize the non-lignified parenchyma cells in the wood of Cactaceae is extremely diversified and often not very descriptive, which makes it difficult to establish homologies and better characterize this tissue. Non-lignified parenchyma cells in the secondary xylem in Cactaceae and Portulacaceae occur in association with the fibrous phase of the wood, often forming true continuous bands. This resembles what some authors call parenchyma wood. The proposal of this study is to demonstrate that, independent of the distribution pattern of the non-lignified parenchyma cells, the terminology used should follow that of the International Association of Wood Anatomists (IAWA) Committee as non-lignified parenchyma and not refer to a parenchymous phase of the wood. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159, 322–329.

Intercellular pectic strands in parenchyma: studies of plant cell walls by scanning electron microscopy.

Rows of pectic strands, each 0.3-0.4�m in diameter, are shown to connect palisade mesophyll cells in regular ladder-like configurations ('pectic scala'). These structures are illustrated in some species of eucalypts, but probably occur in other kinds of plants. Less regular wall filaments can be observed in the intercellular spaces between other types of cells. They are particularly numerous in the parenchyma of species of ferns. These filaments and the pectic scala are readily observable by scanning electron microscopy, but can also be seen in conventional preparations for the light microscope. The structure, formation, chemical composition and possible function of these and other kinds of cell wall protuberances, described in the literature, are discussed.