Background and Aims: Root absorptive characteristics rely on the presence of apoplastic barriers. However, little is known about the establishment of these barriers within a complex root system, particularly in a major portion of them - the lateral roots. In Zea mays L., the exodermis differentiates under the influence of growth conditions. Therefore, the species presents a suitable model to elucidate the cross-talk among environmental conditions, branching pattern and the maturation of barriers within a complex root system involved in the definition of the plant-soil interface. The study describes the extent to which lateral roots differentiate apoplastic barriers in response to changeable environmental conditions. Methods: The branching, permeability of the outer cell layers and differentiation of the endo- and exodermis were studied in primary roots and various laterals under different types of stress of agronomic importance (salinity, heavy metal toxicity, hypoxia, etc.). Histochemical methods, image analysis and apoplastic tracer assays were utilized. Key Results: The results show that the impact of growth conditions on the differentiation of both the endodermis and exodermis is modulated according to the type/diameter of the root. Fine laterals clearly represent that portion of a complex root system with a less advanced state of barrier differentiation, but with substantial ability to modify exodermis differentiation in response to environmental conditions. In addition, some degree of autonomy in exodermal establishment of Casparian bands (CBs) vs. suberin lamellae (SLs) was observed, as the absence of lignified exodermal CBs did not always fit with the lack of SLs. Conclusions: This study highlights the importance of lateral roots, and provides a first look into the developmental variations of apoplastic barriers within a complex root system. It emphasizes that branching and differentiation of barriers in fine laterals may substantially modulate the root system-rhizosphere interaction.
Nitrogen (N) is an essential macronutrient that limits agricultural productivity, and both low and high N supply have been suggested to alter plant growth. The overall aim of this work is to study the impact of nitrate (NO3(-)) in maize yield and the possible causes that induce this alteration. High NO3(-) doses did not increase the yield of maize grown neither in the field nor under controlled conditions. In fact, plants grown under controlled conditions for 45 days with NO3(-) concentrations over 5mM showed a decrease in biomass production. This reduction was perceptible in shoots prior to roots, where phytomer expansion was reduced. Cell size and number were also reduced in the leaves of plants with high NO3(-). This alteration was correlated with the increase of 1-aminocyclopropane-1-carboxylic acid in leaves, which was probably translocated from the roots in order to synthesize ethylene. Cytokinins (CKs) also showed a relevant role in this inhibitory effect, increasing in high NO3(-) plants with a reduction in root and shoot growth, inhibition of apical dominance and a strong decrease of leaf expansion, symptoms described previously as "CK syndrome". We propose that high NO3(-) inhibits maize growth by causing hormonal alterations that modify plant growth from cell to whole plant.
- MeSH
- aminokyseliny cyklické metabolismus MeSH
- biomasa MeSH
- cytokininy metabolismus MeSH
- dusičnany farmakologie MeSH
- dusík metabolismus MeSH
- epidermis rostlin cytologie účinky léků růst a vývoj MeSH
- kořeny rostlin cytologie účinky léků růst a vývoj MeSH
- kukuřice setá cytologie účinky léků růst a vývoj MeSH
- listy rostlin cytologie účinky léků růst a vývoj MeSH
- výhonky rostlin cytologie účinky léků růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
Shoot branching is a primary contributor to plant architecture, evolving independently in flowering plant sporophytes and moss gametophytes. Mechanistic understanding of branching is largely limited to flowering plants such as Arabidopsis, which have a recent evolutionary origin. We show that in gametophytic shoots of Physcomitrella, lateral branches arise by re-specification of epidermal cells into branch initials. A simple model co-ordinating the activity of leafy shoot tips can account for branching patterns, and three known and ancient hormonal regulators of sporophytic branching interact to generate the branching pattern- auxin, cytokinin and strigolactone. The mode of auxin transport required in branch patterning is a key divergence point from known sporophytic pathways. Although PIN-mediated basipetal auxin transport regulates branching patterns in flowering plants, this is not so in Physcomitrella, where bi-directional transport is required to generate realistic branching patterns. Experiments with callose synthesis inhibitors suggest plasmodesmal connectivity as a potential mechanism for transport.
- MeSH
- biologické modely MeSH
- biologický transport účinky léků MeSH
- cytokininy biosyntéza MeSH
- epidermis rostlin cytologie růst a vývoj MeSH
- geneticky modifikované rostliny MeSH
- kyseliny indoloctové metabolismus farmakologie MeSH
- laktony farmakologie MeSH
- mechy účinky léků růst a vývoj MeSH
- morfogeneze účinky léků MeSH
- mutace genetika MeSH
- regulace genové exprese u rostlin účinky léků MeSH
- regulátory růstu rostlin farmakologie MeSH
- rostlinné proteiny metabolismus MeSH
- rozvržení tělního plánu účinky léků MeSH
- výhonky rostlin účinky léků růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
BACKGROUND AND AIMS: The maize lrt1 (lateral rootless1) mutant is impaired in its development of lateral roots during early post-embryonic development. The aim of this study was to characterize, in detail, the influences that the mutation exerts on lateral root initiation and the subsequent developments, as well as to describe the behaviour of the entire plant under variable environmental conditions. METHODS: Mutant lrt1 plants were cultivated under different conditions of hydroponics, and in between sheets of moist paper. Cleared whole mounts and anatomical sections were used in combination with both selected staining procedures and histochemical tests to follow root development. Root surface permeability tests and the biochemical quantification of lignin were performed to complement the structural data. KEY RESULTS: The data presented suggest a redefinition of lrt1 function in lateral roots as a promoter of later development; however, neither the complete absence of lateral roots nor the frequency of their initiation is linked to lrt1 function. The developmental effects of lrt1 are under strong environmental influences. Mutant primordia are affected in structure, growth and emergence; and the majority of primordia terminate their growth during this last step, or shortly thereafter. The lateral roots are impaired in the maintenance of the root apical meristem. The primary root shows disturbances in the organization of both epidermal and subepidermal layers. The lrt1-related cell-wall modifications include: lignification in peripheral layers, the deposition of polyphenolic substances and a higher activity of peroxidase. CONCLUSIONS: The present study provides novel insights into the function of the lrt1 gene in root system development. The lrt1 gene participates in the spatial distribution of initiation, but not in its frequency. Later, the development of lateral roots is strongly affected. The effect of the lrt1 mutation is not as obvious in the primary root, with no influences observed on the root apical meristem structure and maintenance; however, development of the epidermis and cortex are impaired.
- MeSH
- buněčná stěna metabolismus MeSH
- epidermis rostlin anatomie a histologie genetika růst a vývoj MeSH
- hydroponie MeSH
- kořeny rostlin cytologie genetika růst a vývoj MeSH
- kukuřice setá cytologie genetika růst a vývoj MeSH
- lignin metabolismus MeSH
- meristém cytologie genetika růst a vývoj MeSH
- mutace MeSH
- polyfenoly metabolismus MeSH
- regulace genové exprese u rostlin * MeSH
- rostlinné proteiny genetika metabolismus MeSH
- semenáček cytologie genetika růst a vývoj MeSH
- výhonky rostlin cytologie genetika růst a vývoj MeSH
- vývojová regulace genové exprese MeSH
- životní prostředí MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
