scholarly journals A Positive Tropism of Rice Roots toward a Nutrient Source

2019 ◽  
Vol 61 (3) ◽  
pp. 546-553
Author(s):  
Kiyoshi Yamazaki ◽  
Yoshihiro Ohmori ◽  
Toru Fujiwara
Keyword(s):  
Cell Elongation ◽  
Lateral Roots ◽  
Fourth Power ◽  
Nutrient Concentrations ◽  
Root Tips ◽  
High Moisture ◽  
Nutrient Source ◽  
Directional Growth ◽  
Rice Roots ◽  
Differential Cell

Abstract Plants take up water and nutrients through roots, and uptake efficiency depends on root behavior. Roots recognize the moisture gradient in the soil and grow toward the direction of high moisture. This phenomenon is called hydrotropism, and it contributes to efficient water uptake. As nutrients in soil are also unevenly distributed, it is beneficial for plants to grow their roots in the direction of increasing nutrient concentrations, but such a phenomenon has not been demonstrated. Here, we describe the directional growth of roots in response to a nutrient gradient. Using our assay system, the gradient of a nitrogen nutrient, NH4+, was sufficient to stimulate positive tropic responses of rice lateral roots. This phenomenon is a tropism of plant roots to nutrients; hence, we propose the name ‘nutritropism’. As well as other tropisms, differential cell elongation was observed before the elongation zone during nutritropism, but the pattern promoting cell elongation preferentially on the non-stimulated side was opposite to those in root hydrotropism and gravitropism. Our evaluation of the NH4+ gradient suggested that the root tips responded to a sub-micromolar difference in NH4+ concentration on both sides of the root. Hydrotropism, gravitropism and phototropism were described in plants as the ‘power of movement’ by Charles and Francis Darwin in 1880, and these three tropisms have attracted the attention of plant scientists for more than 130 years. Our discovery of nutritropism represents the fourth ‘power of movement’ in plants and provides a novel root behavioral property used by plants to acquire nutrients efficiently.

scholarly journals An Endoglucanase Is Involved in Infection of Rice Roots by the Not-Cellulose-Metabolizing Endophyte Azoarcus Sp. Strain BH72

2006 ◽  
Vol 19 (2) ◽  
pp. 181-188 ◽  
Author(s):  
Barbara Reinhold-Hurek ◽  
Tamara Maes ◽  
Sabrina Gemmer ◽  
Marc Van Montagu ◽  
Thomas Hurek
Keyword(s):  
Xanthomonas Campestris ◽  
Bacterial Colonization ◽  
Lateral Roots ◽  
Glycosyl Hydrolases ◽  
Root Tips ◽  
Endophytic Colonization ◽  
Rice Roots ◽  
Colonization Process ◽  
Kallar Grass ◽  
Microscopic Inspection

The nitrogen-fixing endophyte Azoarcus sp. strain BH72 infects roots of Kallar grass and rice inter- and intra-cellularly and can spread systemically into shoots without causing symptoms of plant disease. Although cellulose or its breakdown products do not support growth, this strain expresses an endoglucanase, which might be involved in infection. Sequence analysis of eglA places the secreted 34-kDa protein into the glycosyl hydrolases family 5, with highest relatedness (40% identity) to endoglucanases of the phytopathogenic bacteria Xanthomonas campestris and Ralstonia solanacearum. Transcriptional regulation studied by eglA:: gusA fusion was not significantly affected by cellulose or its breakdown products or by microaerobiosis. Strongest induction (threefold) was obtained in bacteria grown in close vicinity to rice roots. Visible sites of expression were the emergence points of lateral roots and root tips, which are the primary regions of ingress into the root. To study the role in endophytic colonization, eglA was inactivated by transposon mutagenesis. Systemic spreading of the eglA mutant and of a pilAB mutant into the rice shoot could no longer be detected by polymerase chain reaction. Microscopic inspection of infection revealed that the intracellular colonization of root epidermis cells was significantly reduced in the eglA-mutant BHE6 compared with the wild type and partially restored in the complementation mutant BHRE2 expressing eglA. This provides evidence that Azoarcus sp. endoglucanase is an important determinant for successful endophytic colonization of rice roots, suggesting an active bacterial colonization process.

scholarly journals Effects of Phosphate Shortage on Root Growth and Hormone Content of Barley Depend on Capacity of the Roots to Accumulate ABA

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1722
Author(s):  
Lidiya Vysotskaya ◽  
Guzel Akhiyarova ◽  
Arina Feoktistova ◽  
Zarina Akhtyamova ◽  
Alla Korobova ◽  
...  
Keyword(s):  
Root Growth ◽  
Lateral Roots ◽  
Primary Root ◽  
Growth Responses ◽  
Root Tips ◽  
P Deficiency ◽  
Root Branching ◽  
Auxin Concentration ◽  
Shoot Mass ◽  
Primary Root Length

Although changes in root architecture in response to the environment can optimize mineral and water nutrient uptake, mechanisms regulating these changes are not well-understood. We investigated whether P deprivation effects on root development are mediated by abscisic acid (ABA) and its interactions with other hormones. The ABA-deficient barley mutant Az34 and its wild-type (WT) were grown in P-deprived and P-replete conditions, and hormones were measured in whole roots and root tips. Although P deprivation decreased growth in shoot mass similarly in both genotypes, only the WT increased primary root length and number of lateral roots. The effect was accompanied by ABA accumulation in root tips, a response not seen in Az34. Increased ABA in P-deprived WT was accompanied by decreased concentrations of cytokinin, an inhibitor of root extension. Furthermore, P-deficiency in the WT increased auxin concentration in whole root systems in association with increased root branching. In the ABA-deficient mutant, P-starvation failed to stimulate root elongation or promote branching, and there was no decline in cytokinin and no increase in auxin. The results demonstrate ABA’s ability to mediate in root growth responses to P starvation in barley, an effect linked to its effects on cytokinin and auxin concentrations.

Effects of Trifluralin on Root Morphology and Mineral Status of Wheat (Triticum aestivum) Seedlings

Weed Science ◽  
1984 ◽  
Vol 32 (3) ◽  
pp. 382-387 ◽  
Author(s):  
Barry M. Olson ◽  
Robert B. McKercher ◽  
Edward H. Halstead
Keyword(s):  
Triticum Aestivum ◽  
Lateral Root ◽  
Growth Period ◽  
Nutrient Concentrations ◽  
Root Production ◽  
Root Tips ◽  
Wheat Seedlings ◽  
Mineral Status ◽  
Seminal Roots ◽  
Percent Nitrogen

Growth chamber studies using one soil investigated the effects of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.0, 0.4, and 0.8 ppmw on the root development and the mineral status of wheat (Triticum aestivumL. ‘Neepawa’) seedlings. The 0.8-ppmw trifluralin rate increased the number of seminal roots, reduced lateral root production, decreased root extension, caused root tips to swell (club-like appearance), and reduced root dry weights. However, 0.4-ppmw trifluralin caused only slight damage to the seedlings. Towards the end of the two-week growth period, damaged seedlings showed signs of recovery, which included an increased number of seminal roots, development of normal root extensions from clubbed root tips, and development of normal lateral root patterns. Trifluralin increased percent calcium and magnesium and decreased percent nitrogen, phosphorus, and potassium in wheat plants. The nutrient concentrations were more affected in 21-day-old plants than in 35-day-old plants, indicating the wheat seedlings were able to recover from trifluralin injury.

Deep modifications of the microbiome of rice roots infected by the parasitic nematode Meloidogyne graminicola in highly infested fields in Vietnam

2020 ◽  
Vol 96 (7) ◽  
Author(s):  
Anne-Sophie Masson ◽  
Hai Ho Bich ◽  
Marie Simonin ◽  
Hue Nguyen Thi ◽  
Pierre Czernic ◽  
...  
Keyword(s):  
Parasitic Nematode ◽  
Bacterial Community Composition ◽  
Root Knot Nematode ◽  
Root Tips ◽  
Meloidogyne Graminicola ◽  
Rice Roots ◽  
Functional Capabilities ◽  
Infected Root ◽  
Plant Parasitic ◽  
Root Microbiome

ABSTRACT Meloidogyne graminicola, also known as the rice root-knot nematode, is one of the most damaging plant-parasitic nematode, especially on rice. This obligate soilborne parasite induces the formation of galls that disturb the root morphology and physiology. Its impact on the root microbiome is still not well described. Here, we conducted a survey in Northern Vietnam where we collected infected (with galls) and non-infected root tips from the same plants in three naturally infested fields. Using a metabarcoding approach, we discovered that M. graminicola infection caused modifications of the root bacterial community composition and network structure. Interestingly, we observed in infected roots a higher diversity and species richness (+24% observed ESVs) as well as a denser and more complex co-occurrence network (+44% nodes and +136% links). We identified enriched taxa that include several hubs, which could serve as potential indicators or biocontrol agents of the nematode infection. Moreover, the community of infected roots is more specific suggesting changes in the functional capabilities to survive in the gall environment. We thus describe the signature of the gall microbiome (the ‘gallobiome’) with shifting abundances and enrichments that lead to a strong restructuration of the root microbiome.

Temperature Effects on Absorption and Translocation of Trifluralin and Methazole in Peanuts

Weed Science ◽  
1972 ◽  
Vol 20 (4) ◽  
pp. 285-289 ◽  
Author(s):  
K. Hawxby ◽  
E. Basler ◽  
P. W. Santelmann
Keyword(s):  
Temperature Effects ◽  
Lateral Root ◽  
Initial Rate ◽  
Lateral Roots ◽  
Leaf Tissue ◽  
Root Tips ◽  
Plant Parts ◽  
Tap Root ◽  
Rate Of Absorption ◽  
Nutrient Solutions

The absorption and translocation of14C-labeled α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) and 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione methazole from nutrient solutions of various temperatures by(Arachis hypogaeaL. ‘Starr’) seedlings were determined. The accumulation of trifluralin in roots at 24 hr after exposure to trifluralin was greatest at 21 C and decreased at higher temperatures up to 38 C. The amounts of trifluralin translocated and accumulated in hypocotyls, tops, and cotyledons were small but generally increased with temperature. The initial rate of absorption of trifluralin was greater in excised lateral root tips than in tap root tips, but there was a greater accumulation in excised tap roots at 24 hr. The initial rates of absorption were higher for excised lateral roots at high temperatures. Total absorption of trifluralin at equilibrium was not proportional to the initial rates of absorption but was highest at low (21 C) and high (38 C) temperatures for excised lateral roots. The absorption of methazole by roots and translocation to other plant parts increased linearly with temperature, and it tended to accumulate in the mature leaf tissue.

scholarly journals Expression Studies on AUX1-like Genes in Medicago truncatula Suggest That Auxin Is Required at Two Steps in Early Nodule Development

2001 ◽  
Vol 14 (3) ◽  
pp. 267-277 ◽  
Author(s):  
Françoise de Billy ◽  
Cathy Grosjean ◽  
Sean May ◽  
Malcolm Bennett ◽  
Julie V. Cullimore
Keyword(s):  
Medicago Truncatula ◽  
Lateral Root ◽  
Sequence Similarity ◽  
Lateral Roots ◽  
Peripheral Region ◽  
Nodule Development ◽  
Central Position ◽  
Root Tips ◽  
High Sequence Similarity ◽  
Primary Roots

Medicago truncatula contains a family of at least five genes related to AUX1 of Arabidopsis thaliana (termed MtLAX genes for Medicago truncatula-like AUX1 genes). The high sequence similarity between the encoded proteins and AUX1 implies that the MtLAX genes encode auxin import carriers. The MtLAX genes are expressed in roots and other organs, suggesting that they play pleiotropic roles related to auxin uptake. In primary roots, the MtLAX genes are expressed preferentially in the root tips, particularly in the provascular bundles and root caps. During lateral root and nodule development, the genes are expressed in the primordia, particularly in cells that were probably derived from the pericycle. At slightly later stages, the genes are expressed in the regions of the developing organs where the vasculature arises (central position for lateral roots and peripheral region for nodules). These results are consistent with MtLAX being involved in local auxin transport and suggest that auxin is required at two common stages of lateral root and nodule development: development of the primordia and differentiation of the vasculature.

scholarly journals ECHIDNA-mediated post-Golgi trafficking of auxin carriers for differential cell elongation

2013 ◽  
Vol 110 (40) ◽  
pp. 16259-16264 ◽  
Author(s):  
Y. Boutte ◽  
K. Jonsson ◽  
H. E. McFarlane ◽  
E. Johnson ◽  
D. Gendre ◽  
...  
Keyword(s):  
Cell Elongation ◽  
Differential Cell

scholarly journals PIN7 auxin carrier is a terminator of radial root expansion in Arabidopsis thaliana

2018 ◽  
Author(s):  
Michel Ruiz Rosquete ◽  
Jürgen Kleine-Vehn
Keyword(s):  
Radial Growth ◽  
Lateral Roots ◽  
Root Systems ◽  
Plateau Phase ◽  
Directional Growth ◽  
Auxin Signalling ◽  
Molecular Determinants ◽  
Auxin Carrier ◽  
Auxin Efflux Carriers ◽  
Bending Response

AbstractDirectional growth of lateral roots is critical for radial expansion and soil coverage. Despite its importance, almost nothing is known about its molecular determinants. Initially, young lateral roots (LRs) grow away from the parental root maintaining the angle acquired shortly after emergence. A second downwards bending response to gravity terminates the so-called plateau phase and thereby limits the radial root expansion. Here we show that the exit from the plateau phase correlates with an increase in auxin signalling at the tip of LRs. Moreover, the increase in auxin levels induces the termination of the plateau phase, which requires PIN auxin efflux carriers. Our data suggests that the developmental increase of auxin triggers the preferential de-repression of PIN7 in gravity-sensing columella cells. The subsequent polarization of PIN7 heralds the bending towards gravity and, hence, the exit from the plateau phase. This developmental framework reveals the distinct roles of PIN auxin efflux carriers in controlling the radial growth of root systems.

scholarly journals Tissue growth constrains root organ outlines into an isometrically scalable shape

Development ◽  
2021 ◽  
Vol 148 (4) ◽  
pp. dev196253
Author(s):  
Motohiro Fujiwara ◽  
Tatsuaki Goh ◽  
Satoru Tsugawa ◽  
Keiji Nakajima ◽  
Hidehiro Fukaki ◽  
...  
Keyword(s):  
Plant Root ◽  
Lateral Roots ◽  
Time Lapse ◽  
Tissue Growth ◽  
Root Tip ◽  
Root Tips ◽  
Developmental Constraints ◽  
Primary Roots ◽  
Catenary Curve ◽  
Expansion Force

ABSTRACTOrgan morphologies are diverse but also conserved under shared developmental constraints among species. Any geometrical similarities in the shape behind diversity and the underlying developmental constraints remain unclear. Plant root tip outlines commonly exhibit a dome shape, which likely performs physiological functions, despite the diversity in size and cellular organization among distinct root classes and/or species. We carried out morphometric analysis of the primary roots of ten angiosperm species and of the lateral roots (LRs) of Arabidopsis, and found that each root outline was isometrically scaled onto a parameter-free catenary curve, a stable structure adopted for arch bridges. Using the physical model for bridges, we analogized that localized and spatially uniform occurrence of oriented cell division and expansion force the LR primordia (LRP) tip to form a catenary curve. These growth rules for the catenary curve were verified by tissue growth simulation of developing LRP development based on time-lapse imaging. Consistently, LRP outlines of mutants compromised in these rules were found to deviate from catenary curves. Our analyses demonstrate that physics-inspired growth rules constrain plant root tips to form isometrically scalable catenary curves.

scholarly journals Interplay between Cell Wall and Auxin Mediates the Control of Differential Cell Elongation during Apical Hook Development

2020 ◽  
Vol 30 (9) ◽  
pp. 1733-1739.e3 ◽  
Author(s):  
Bibek Aryal ◽  
Kristoffer Jonsson ◽  
Anirban Baral ◽  
Gloria Sancho-Andres ◽  
Anne-Lise Routier- Kierzkowska ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Elongation ◽  
Apical Hook ◽  
Differential Cell
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