Regions Of Leaf Blade Research Articles

Arabidopsis Leaf Flatness Is Regulated by PPD2 and NINJA through Repression of CYCLIN D3 Genes.

In Arabidopsis (Arabidopsis thaliana), reduced expression of the transcriptional regulator PEAPOD2 (PPD2) results in propeller-like rosettes with enlarged and dome-shaped leaves. However, the molecular and cellular processes underlying this peculiar phenotype remain elusive. Here, we studied the interaction between PPD2 and NOVEL INTERACTOR OF JAZ (NINJA) and demonstrated that ninja loss-of-function plants produce rosettes with dome-shaped leaves similar to those of ppd mutants but without the increase in size. We showed that ninja mutants have a convex-shaped primary cell cycle arrest front, putatively leading to excessive cell division in the central leaf blade region. Furthermore, ppd and ninja mutants have a similar increase in the expression of CYCLIN D3;2 (CYCD3;2), and ectopic overexpression of CYCD3;2 phenocopies the ppd and ninja rosette and leaf shape phenotypes without affecting the size. Our results reveal a pivotal contribution of NINJA in leaf development, in addition to its well-studied function in jasmonate signaling, and imply a new function for D3-type cyclins in, at least partially, uncoupling the size and shape phenotypes of ppd leaves.

AN APPROACH ON ANATOMICAL STRUCTURE OF CHAETOSTOMA GLAZIOVII COGN – MELASTOMATACEAE – AND ITS SUCCESSFUL ESTABLISHMENT AT HIGH-ALTITUDE FIELDS

Chaetostoma glaziovii Cogn. is an endemic species of the Brazilian flora and grows exclusively in fields at elevations above 2000 meters. It belongs to Melastomataceae family, Microlicieae tribe, which presents little variation on vegetative organs, making it difficult to identify sterile individuals. Anatomical studies, using optical and scanning electron microscopes are carried on comparing the data with the anatomical characteristics of xeromorphic plants, cited in the literature, to check its similarities. This study aims, also, highlight data that may contribute to characterization of the species due to the great similarities among sterile individuals within the tribe. Leaf and stem anatomical data of C. glaziovii are interpreted considering climatic factors, aiming to understand the species’ successful establishment in an environment characterized by intense light exposure, strong winds and extreme temperatures. It is noteworthy the great amount of fibers on the abaxial and marginal regions of leaf blade, forming an armor against environmental aggressions. In addition, this characteristic is valued from the taxonomic perspective because no other species of the tribe exhibits such extensive fiber development. The material was collected in the Itatiaia National Park at an altitude of 2350 meters, latitude S 22° 23' 26'' and longitude W 44o 40' 17''. Histochemical tests were performed on unfixed samples to identify starch grains, lipids, phenolic compounds, glycides and crystals. The anatomical data revealed that some characteristics of C. glaziovii are like those found on xeromorphic plants and are important for its identification beyond to contribute for understanding the intricate plant-environment relationships.

TheKnottedleaf blade is a mosaic of blade, sheath, and auricle identities

AbstractThe dominantKnotted‐1mutations in maize alter development of the leaf blade. Sporadic patches of localized growth, or knots, and fringes of ectopic ligule occur along lateral veins of mutant leaf blades. In addition, bundle sheaths do not completely encircle lateral veins on mutant leaf blades. We have compared mutant leaf blades with wild‐type leaves to determine the precise nature of the perturbed regions. Our analysis includes characterization of epidermal cell shapes, localization of photosynthetic proteins and histology of the leaf. We show that mutant leaf blades are a mosaic of leaf organ components. Affected regions of mutant leaf blades resemble either sheath or auricle tissue in both external and internal features. This conversion of blade cells represents an acropetal shift of more basal parts of the leaf blade region and correlates with previously identified ectopic expression of theKnotted‐1protein in the leaf blade. We propose that inappropriate expression ofKn1interferes with the process of establishment of cell identities, resulting in early termination of the normal blade development program or precocious expression of the sheath and auricle development programs. © 1994 Wiley‐Liss, Inc.

The rotated-lamina syndrome. I. Ulmaceae

In a number of plants, mostly woody, the components of the buds are arranged so that the laminae of the young leaves all face towards the same (upper) side of the bud, rather than towards the bud apex; in axillary buds they usually face towards the parent axis. This situation has been known for many years. For convenience, the general case is here called the rotated-lamina syndrome. There have been very few developmental investigations of how the laminae attain their unusual orientation, and these have come to different conclusions about cases in the Ulmaceae. This paper reports a detailed investigation of the syndrome in Ulmus glabra and Zelkova serrata, with comparative observations on other Ulmaceae, including cases in Celtis that do not exhibit the syndrome. The syndrome arises by different means in Ulmus and Zelkova. In Ulmus the leaf primordium is asymmetrical from the outset, the leaf blade region is obliquely dorsiventral from an early stage, and further asymmetrical growth of the leaf buttress rotates the whole leaf blade region into its final orientation as it develops. Individual shoots show heteroblastic development in progressing from bud scale to foliage leaf initiation, in increasing accentuation of the rotated-lamina syndrome, and in an increasing degree of dorsiventrality. In Zelkova, as previously described, the leaf blade region appears first as a radially symmetrical upgrowth, and it acquires dorsiventral symmetry directly in the rotated position. In Celtis spp. the lamina arises in a quite normal orientation, but reorients as it emerges from the bud. The leaf primordia of all species studied show asymmetry in other aspects, particularly in respect of stipule development, and these seem to be general features of the organisation of dorsiventral shoots. Key words: Ulmus, Zelkova, Celtis, leaf, development, dorsiventrality, lamina rotation.

The rotated-lamina syndrome. III. Cases in Begonia, Corylus, Magnolia, Pellionia, Prunus, and Tilia

The rotated-lamina syndrome occurs in all adult shoots of Tilia × europaea, and in lateral shoots of Corylus spp. and Prunus laurocerasus. Corylus and Prunus also have orthotropic radially symmetrical shoots that have normal leaf orientation. Development of the syndrome in leaf primordia in Tilia and Corylus is similar to that previously described in Ulmus, i.e., the leaf primordium is initially asymmetrical so that the leaf blade component of the primordium arises facing only obliquely towards the shoot apex, and further asymmetrical outgrowth of the leaf buttress brings the leaf blade region into the rotated position. Leaves of Begonia foliosa and the ventral leaves of (anisophyllous) Pellionia pulchra arise from initially symmetrical primordia, and lamina rotation occurs by asymmetric growth at the base of the leaf blade region. The process is similar to that in the woody examples but occurs at a proportionately later stage of leaf development. Development of the syndrome in Prunis laurocerasus and Magnolia × soulangeana differs considerably. Primordia are slightly asymmetrical but have normal dorsiventrality at first, but when the lamina arises the two edges of the leaf blade grow towards the same (upper) side of the bud, and this is responsible for most of the appearance of rotation. In general the upper stipule is initially larger than the lower and arises much earlier in Corylus and Tilia. Leaves that have normal orientation in Corylus and Prunus develop from quite symmetrical primordia, but those of Cotylus may show some asymmetry of stipule development. Shoots of all cases can be considered to show heteroblastic growth, and the early part of the heteroblastic sequence is prolonged in the orthotropic shoots with normally oriented leaves in Corylus and Prunus. The morphological and morphogenetic significance of the rotated-lamina syndrome is discussed. Key words: Begonia, Corylus, Magnolia, Pellionia, Prunus, Tilia, leaf, development, dorsiventrality, lamina rotation.