Differentiation Of Endodermis Research Articles

Advances in the development and function of plant root endodermis

<p indent="0mm">Root, an important underground vegetative organ of plants, plays diversified roles in plant lifecycle, including fixation and support, absorption and transportation, storage and reproduction. In meristem zone of root tip, the apical meristem is continuously divided to produce new cells, promoting the growth of root tip. Mature tissues formed through primary growth constituted the primary structure of plant roots. Water and mineral ions entered the epidermis of root, passed through the outer cortex, cortex, and endodermis in a radial direction, and reached the middle column, and were transported upward in xylem through transpiration, so as to meet the needs of aboveground part. The endodermis lies the innermost cortex surrounding the central vascular tissue system, as is constructed by only monolayer cells Endodermis is a cylindrical boundary separating the central vascular tissue from the outer cortex, and is an extracellular barrier for plant selective nutrient absorption. There were mainly two stages in differentiation of endodermis, of which in differentiation stage I, lignin was continuously deposited on lateral and radial walls of endodermis cells near the root tip, forming Casparian strips. The nature of Casparian strips was a local modification on the primary wall of endodermal layer, which was formed by the lignin polymer “impregnate” the primary wall. The complete Casparian strips show a continuous belt thickening structure, which blocked the apoplast transport pathway, prevented the diffusion of solutes between cell walls, and forced solutes to transport through the plasma membrane. In differentiation stage II, and based on the Casparian strips, hydrophobic suberin was deposited on six cell walls of endodermal cells, forming suberin lamellae structure, which inhibited the transmembrane transport of substances and was a protective barrier structure. Development of Casparian strips and suberin lamellae structure are regulated by their own growth and development mechanism and closely regulated by external environmental factors. The structure of endodermis could respond to the stress environment, and the lack of necessary mineral elements, including potassium, iron or sulfur, may cause changes in composition and structure of the Casparian strips and suberin lamellae. The above change was called plant phenotypic plasticity, whose most significant function was to support plants to adapt to the environment, integrate environmental information, optimize nutrient absorption, and maintain ion homeostasis in plants, so as to improve their survival under stressful environment. A complete suberin lamellae barrier was capable of preventing calcium ions from flowing in and potassium ions from seeping out, maintaining the balance of calcium/potassium ions in plants, supporting to regulate calcium signaling system, promoting plants photosynthesis, and improving stress resistance of crops. The paper comprehensively introduced the general development mode of plant endodermis, and the structure, concluded the composition and formation regulation mechanism of Casparian strips and suberin lamellae, and discussed the changing law of endodermis plasticity responding to abiotic stress and its importance for maintaining plant ion homeostasis, as well as prospected the future research direction, providing a new idea for cultivating new stress-resistant species.

Minimum requirements for changing and maintaining endodermis cell identity in the Arabidopsis root.

Changes in gene regulation during differentiation are governed by networks of transcription factors. The Arabidopsis root endodermis is a tractable model to address how transcription factors contribute to differentiation. We used a bottom-up approach to understand the extent to which transcription factors required for endodermis differentiation can confer endodermis identity to a non-native cell-type. Our results show the transcription factors SHORTROOT and MYB36 alone have limited ability to induce ectopic endodermal features in the absence of additional cues. The stele-derived signaling peptide CIF2 stabilizes SHORTROOT-induced endodermis identity acquisition. The outcome is a partially impermeable barrier deposited in the sub-epidermal cell layer, which has a transcriptional signature similar to the endodermis. These results demonstrate other root cell-types can be forced to differentiate into endodermis and highlights a previously unappreciated role for receptor-kinase signaling in maintaining endodermis identity.

The endodermis as a checkpoint for nutrients.

Contents 1604 I. 1604 II. 1604 III. 1605 IV. 1608 V. 1609 1609 References 1609 SUMMARY: Plant roots forage the soil for nutrients and transport them upwards to the aerial parts. Nutrients entering the plant are transported through the concentric layers of epidermis, cortex and endodermis before reaching the central vasculature. The endodermis is the innermost cortical cell layer that surrounds the vasculature. The endodermis forms barriers, the Casparian strips and suberin lamellae, which have been assumed to play a major role in controlling nutrient acquisition. However, the molecular network controlling its differentiation has started to be investigated only recently, giving an unprecedented opportunity to address the role of these barriers in plant nutrition. This insight aims to present recent advances regarding endodermis differentiation, its function as a barrier for nutrients and its developmental plasticity, all pointing to a pivotal role of the endodermis as a checkpoint for nutrients.

Zonal responses of sensitive vs. tolerant wheat roots during Al exposure and recovery

Aluminium (Al) irreversibly inhibits root growth in sensitive, but not in some tolerant genotypes. To better understand tolerance mechanisms, seedlings from tolerant (‘Barbela 7/72’ line) and sensitive (‘Anahuac’) Triticum aestivum L. genotypes were exposed to AlCl3 185μM for: (a) 24h followed by 48h without Al (recovery); (b) 72h of continuous exposure. Three root zones were analyzed (meristematic (MZ), elongation (EZ) and hairy (HZ)) for callose deposition, reserves (starch and lipids) accumulation, endodermis differentiation and tissue architecture. Putative Al-induced genotoxic or cytostatic/mytogenic effects were assessed by flow cytometry in root apices.Tolerant plants accumulated less Al, presented less root damage and a less generalized callose distribution than sensitive ones. Starch and lipid reserves remained constant in tolerant roots but drastically decreased in sensitive ones. Al induced different profiles of endodermis differentiation: differentiation was promoted in EZ and HZ, respectively, in sensitive and tolerant genotypes. No ploidy changes or clastogenicity were observed. However, differences in cell cycle blockage profiles were detected, being less severe in tolerant roots. After Al removal, only the ‘Barbela 7/72’ line reversed Al-induced effects to values closer to the control, mostly with respect to callose deposition and cell cycle progression. We demonstrate for the first time that: (a) cell cycle progression is differently regulated by Al-tolerant and Al-sensitive genotypes; (b) Al induces callose deposition >3cm above root apex (in HZ); (c) callose deposition is a transient Al-induced effect in tolerant plants; and (d) in HZ, endodermis differentiation is also stimulated only in tolerant plants, probably functioning in tolerant genotypes as a protective mechanism in addition to callose.

Al toxicity mechanism in tolerant and sensitive rye genotypes

Rye ( Secale cereale L.) plants have high tolerance to Al, and become unique tools to study Al-toxicity and tolerance mechanisms. To better understand if and how Al-induced root growth inhibition is related with root histological differentiation, nutrient balances and cell cycle dynamics, tolerant (AT6) and sensitive (AS6) rye lines were exposed for 24 h to 1.1 mM Al. After that period, half of plants were transferred to medium without Al, while the other group was maintained with Al for more 48 h. AS6 plants showed evident and irreversible root growth inhibition, decreases in water content, organic matter and carbohydrate reserves. Also, roots of this line showed greater increases in Ca levels and changes in anatomy (e.g. thickness). Data revealed that AS6 plants accumulate more Al in roots and leaves, suggesting more Al translocation to the shoots. The two lines responded differently to Al exposure in what concerns endodermis differentiation and cell cycle profile. The tolerant line shows a tendency to arrest in G 0/G 1 phase whereas the sensitive have a tendency to arrest in S phase. These data point to an arrest of cells in specific cell cycle phases, leading to eventual Al-induced cell cycle delay. Taken all together, data show that even short-term exposure to Al leads to root anatomical modifications that in combination with the cell cycle dynamic changes, may represent a plant strategy to cope with this stress.

Differential aluminium changes on nutrient accumulation and root differentiation in an Al sensitive vs. tolerant wheat

Aluminium (Al) toxicity is particularly evident under acid soil conditions limiting crop production, namely in wheat ( Triticum aestivum). Although largely studied, the effects of Al on nutrition imbalances and putative correlations with Al tolerance degrees still remain inconclusive. We investigated the uptake of Al and transport to shoots in one wheat line and one cultivar differing in their tolerance to Al: ‘Barbela 7/72’ (Al-tolerant) and ‘Anahuac’ (Al-sensitive). Wheat seedlings were exposed for a short period to 185 μM AlCl 3 and then grown in the absence of the metal. In general, Al inhibited root growth, mostly in the sensitive cultivar ‘Anahuac’, while water content decreased and organic matter increased in ‘Barbela 7/72’ line. Similar but less evident effects were found in leaves of both genotypes. The profiles of macro- (Ca, K, P, Mg) and micronutrients (Mn, Fe, Zn, B, Cu) accumulation in response to aluminium were analyzed in both genotypes: Al levels increased, mostly in ‘Anahuac’ cultivar. Overall, P, Mg and K levels decreased and Si and Ca increased in roots of both genotypes, while other nutrients had a more inconsistent behaviour. Histological data showed that ‘Barbela 7/72’ initiated endodermis differentiation more efficiently than ‘Anahuac’, at the hairy root zone. These data show that: (a) Al negatively interferes with P, Mg and K in wheat and (b) Al interactions with some nutrients depend on the level of plant tolerance. Finally, data also provide support to the hypothesis that endodermis differentiation may be stimulated limiting Al accumulation/allocation in roots of the tolerant wheat landrace.

A phi Layer in Roots of Ceratonia siliqua L

Abstract:The central cylinder of the primary root of the carob tree (Ceratonia siliqua) is encircled by a layer of cells with wall thickenings, known as a phi (φ) cell layer. The development of the φ layer and the chemical composition of the cell wall thickenings have been studied in roots of C. siliqua. The results reveal the presence of condensed tannins in the mature phi thickenings and that the development of the φ layer is asynchronous: at 0–1 cm from the root tip φ thickenings appear before endodermis differentiation at the sites opposite phloem, at 1–4 cm new φ thickenings are developed at the sites opposite xylem, at 4–7 cm the φ layer consists of two layers of cells and it completely encloses the central cylinder.

A86 Potential effects of slower than expected recruitment and proposed changes in eligibility criteria on power in a randomized controlled trial

Rye (Secale cereale L.) plants have high tolerance to Al, and become unique tools to study Al-toxicity and tolerance mechanisms. To better understand if and how Al-induced root growth inhibition is related with root histological differentiation, nutrient balances and cell cycle dynamics, tolerant (AT6) and sensitive (AS6) rye lines were exposed for 24 h to 1.1 mM Al. After that period, half of plants were transferred to medium without Al, while the other group was maintained with Al for more 48 h. AS6 plants showed evident and irreversible root growth inhibition, decreases in water content, organic matter and carbohydrate reserves. Also, roots of this line showed greater increases in Ca levels and changes in anatomy (e.g. thickness). Data revealed that AS6 plants accumulate more Al in roots and leaves, suggesting more Al translocation to the shoots. The two lines responded differently to Al exposure in what concerns endodermis differentiation and cell cycle profile. The tolerant line shows a tendency to arrest in G0/G1 phase whereas the sensitive have a tendency to arrest in S phase. These data point to an arrest of cells in specific cell cycle phases, leading to eventual Al-induced cell cycle delay. Taken all together, data show that even short-term exposure to Al leads to root anatomical modifications that in combination with the cell cycle dynamic changes, may represent a plant strategy to cope with this stress.

Comparative investigations on the differentiation of the endodermis and the development of the Hartig net in mycorrhizae of Picea abies and Larix decidua

The differentiation of the endodermis of mycorrhizal roots of Picea abies and Larix decidua was investigated by means of light and transmission electron microscopy and with fluorescence techniques. The initiation and differentiation of the Hartig net were recorded. Differences between the two tree species were found, as were differences between the two tree species and angiosperms. The Casparian band developed immediately after the origin of endodermal cells from the meristem in mycorrhizae of both tree species. In L. decidua only the primary endodermis was present in most mycorrhizal laterals. The secondary structure of the endodermis was restricted to main roots and proximal parts of larch mycorrhizae. In P. abies mycorrhizae, however, the secondary stage of the endodermis developed soon after the primary endodermis and was characterized by regular alternation of short, active passage cells and elongated, rapidly degenerating cells, the inner surface of which was covered by a thick suberin layer. Hartig net development started in P. abies short roots only after the differentiation of endodermis into the secondary stage, whereas in L. decidua, the Hartig net was already initiated at the primary endodermal stage. Differences were specific for tree species.

A Contribution to the Root Study of the Evergreen Sclerophylls Anatomy of the Primary Root of Quercus coccifera L.

The structure of the primary root of Quercus coccifera , an evergreen sclerophyllous species common in maquis formations in Greece, has been studied by light and electron microscopy with special reference to the differentiation of endodermis. Histochemical identification of phenolic compounds in root tissues has also been carried out. Polyphenolic compound accumulation and extremely thin radial walls of endodermal cells observed in these roots are proposed to be adaptations contributing to a more effective water uptake and transport by the plant.

The Growth of Rice Roots and the Differentiation of Endodermis as Affected by Increasing Transpiration Rate

Two sets of rice plants cultivated under submerged conditions were used, one serving as a test set, the other as a control. One set placed in front of an electric fan where it was exposed to wind velocities from about 0.6 to 1.0 meter per second during day time. The control set was protected from the fan and the natural wind (Fig. 1). The experiments reported here show that the transpiration rate increases about 4.5 to 12 percent and the average length of the crown roots increases about 13 percent by wind. As for the differentiation of the endodermis, though there was no significant difference in the cell wall thickening between both sets, the ratio of the passage cell number opposite to the protoxylem of the stele, were greater in the treated plants. Judging by the data concerning the stimulating effect of the mild wind on root length as well as the number of passage cells, it may be reasonable to think that the ability of roots to absorb water can be induced by the acceleration of transpiration.

On the Correlation between the Endodermis Differentiation and the Water Absorption in the Crown Roots of Rice Plant

The experiments on the water absorption in the different parts of the root of rice plant were carried out, with specially designed micropotometers (Fig. 1). The results obtained show that the water absorbing capacity in the different parts were different, and the most active absorbing zone came between root tip and the part where the first lateral root emerged. The microscopical observation has shown, within this limit, that the differentiation of the endodermis was in the state of casparian dot stage. Furthermore, the differentiation of the xylem vessel in the stele also keep intimate correlation with the differentiation of the endodermis (Fig. 21). Taking in view the results obtained, it is suggested that the stage of the differentiation of the endodermis in a root can be used to detect the zonal differentiation of water absorption.