共查询到20条相似文献,搜索用时 31 毫秒
1.
Renee M. Kosslak Mark A. Chamberlin Reid G. Palmer Benjamin A. Bowen 《The Plant journal : for cell and molecular biology》1997,11(4):729-745
The soybean root necrosis (rn) mutation causes a progressive browning of the root soon after germination that is associated with accumulation of phytoalexins and pathogenesis-related proteins and an increased tolerance to root-borne infection by the fungal pathogen, Phytophthora sojae. Grafting and decapitation experiments indicate that the rn phenotype is root-autonomous at the macroscopic level. However, the onset and severity of browning was modulated in intact plants by exposure to light, as was the extent of lateral root formation, suggesting that both lateral roots and the rn phenotype could be directly or indirectly controlled by similar shoot-derived factors. Browning first occurs in differentiated inner cortical cells adjacent to the stele and is preceded by a wave of autofluorescence that emanates from cortical cells opposite the xylem poles and spreads across the cortex. Before any visible changes in autofluorescence or browning, fragmented DNA was detected by TUNEL (T erminal deoxynucleotidyl transferase-mediated dU TP-digoxigenin n ick e nd l abeling) in small clusters of inner cortical cells that subsequently could be distinguished cytologically from neighboring cells throughout rn root development. Inner cortical cells overlying lateral root primordia in either Rn or rn plants also were stained by TUNEL. Features commonly observed in animal cell apoptosis were confirmed by electron microscopy but, surprisingly, cells with a necrotic morphology were detected alongside apoptotic cells in the cortex of rn roots when TUNEL-positive cells were first observed. The two morphologies may represent different stages of a common pathway for programmed cell death (pcd) in plant roots, or two separate pathways of pcd could be involved. The phenotype of rn plants suggests that the Rn gene could either negatively regulate cortical cell death or be required for cortical cell survival. The possibility of a mechanistic link between cortical cell death in rn plants and during lateral root emergence is discussed. 相似文献
2.
Koi S Fujinami R Kubo N Tsukamoto I Inagawa R Imaichi R Kato M 《American journal of botany》2006,93(5):682-692
In the unusual aquatic Podostemaceae, the root is the leading organ of the plant body and is variously compressed and submerged as it adheres to rock surfaces in rapid water. In an anatomical comparison of the root apical meristems and root caps of 33 species that represent the major lineages of the family, the dorsiventrality of root meristems varied and was classified into four patterns: (1) The root cap is produced outward from a nearly radially symmetrical meristem. (2) The meristem and root cap are markedly dorsiventral; the outermost cells of the hood-shaped cap are acroscopic derivatives from bifacial initials on the ventral side, while the pattern on the dorsal side is similar to pattern 1. (3) Bifacial initials are on both the dorsal and ventral sides. (4) No root cap is present. An evolutionary polarity may be evident from pattern 1 to 2 and then to 3. Pattern 2 arose in the early evolution of the subfamily Podostemoideae and subsequently, pattern 3 arose in species with crustose roots, while the least specialized pattern 1 is retained in Tristichoideae and Weddellinoideae. Pattern 4 characterized by caplessness may have appeared recurrently in Tristichoideae and Podostemoideae. These evolutionary changes in the meristem preceded the specialization of external root morphologies. 相似文献
3.
Although the columella cells of the root cap have been identified as the site of gravity perception, the cellular events that mediate gravity signaling remain poorly understood. To determine if cytoplasmic and/or wall pH mediates the initial stages of root gravitropism, we combined a novel cell wall pH sensor (a cellulose binding domain peptide-Oregon green conjugate) and a cytoplasmic pH sensor (plants expressing pH-sensitive green fluorescent protein) to monitor pH dynamics throughout the graviresponding Arabidopsis root. The root cap apoplast acidified from pH 5.5 to 4.5 within 2 min of gravistimulation. Concomitantly, cytoplasmic pH increased in columella cells from 7.2 to 7.6 but was unchanged elsewhere in the root. These changes in cap pH preceded detectable tropic growth or growth-related pH changes in the elongation zone cell wall by 10 min. Altering the gravity-related columella cytoplasmic pH shift with caged protons delayed the gravitropic response. Together, these results suggest that alterations in root cap pH likely are involved in the initial events that mediate root gravity perception or signal transduction. 相似文献
4.
5.
Root architecture plays an important role in water and nutrient acquisition and in the ability of the plant to adapt to the soil. Lateral root development is the main determinant of the shape of the root system and is controlled by external factors such as nutrient concentration. Here it is shown that lateral root initiation and root gravitropism, two processes that are regulated by auxin, are co-regulated in Arabidopsis. A mathematical model was generated that can predict the effects of gravistimulations on lateral root initiation density and suggests that lateral root initiation is controlled by an inhibitory fields mechanism. Moreover, gene transactivation experiments suggest a mechanism involving a single auxin transport route for both responses. Finally, co-regulation may offer a selective advantage by optimizing soil exploration as supported by a simple quantitative analysis. 相似文献
6.
Removal of the apical 3 mm of the primary root of hydroponically-grown lettuce seedlings 3 or 5 days after sowing, prevented further elongation of the root and increased both the number and total length of lateral roots. The length of the lateral zone, i.e. the distance from the base of the parent root to the lateral nearest the tip, except on one occasion, remained the same as the control in both 3 and 5 day treatments, until the length of the decapitated root (which had ceased elongating) became limiting.Zeatin applied via the roots, at a concentration range from 3 × 10–10 M to 10–8 M reduced tap root extension growth at all concentrations. Lateral root emergence was enhanced by low zeatin concentrations and retarded by higher ones. In general, the lateral zone length was the same in cytokinin-treated plants as in untreated controls. 相似文献
7.
During plant growth and development, root tip performs multifarious functions integrating diverse external and internal stimuli to regulate root elongation and architecture. It is believed that a signal originating from root tip inhibits lateral root formation (LRF). The excision of root tip induced LRF in tomato seedlings associated with accumulation of auxin in pericycle founder cells. The excision of cotyledons slightly reduced LRF, whereas severing shoot from root completely abolished LRF. Exogenous ethylene application did not alter LRF. The response was modulated by light with higher LRF in seedlings exposed to light. Our results indicate that light plays a role in LRF in seedlings by likely modulating shoot derived auxin. 相似文献
8.
Geoperception in the lentil root cap 总被引:1,自引:0,他引:1
Previous analysis showed that, in its initial phase, the geotropic response of Lens culinaris L. roots cannot be explained by a simple action by sliding, pressure or contact of amyloplasts on a sensitive surface located along the longitudinal wall. In this study another mode of action is tested by considering the following parameters as functions of the roots inclination: (1) the distance (d) which the amyloplasts move; (2) their number of contacts (mean c) with parietal cytoplasm; (3) the variable (sin alpha) of the transversal component of the statolith weight (mean M x g sin alpha). It is shown that the initial rate of curvature (mean V), at the various angles, is related to the sedimentation of the amyloplasts by the equation mean V = a log b mean d mean c sin alpha (where a and b are constants). The results obtained prove that the geotropic stimulation is dependent upon the sine of the angle (alpha) of the root inclination and explain the sine rule deviation. The role of statoliths is discussed in the light of recent literature on growth inhibitors which are involved in the geotropic reaction. 相似文献
9.
Mária Luxová 《Biologia Plantarum》1986,28(3):161-167
In addition to the primary seminal primordium, the so-called secondary seminal root primordia are also initiated in a barley
embryo. The primary root primordium is developmentally most advanced. It is formed by root meristem covered with the root
cap, and by a histologically determined region with completed cell division. On germination, the restoration of growth processes
begins in this non-meristematic region of root primordium by cell elongation, with the exception of the zone adjacent to the
scutellar node, the cells of which do not elongate but continue differentiating. In the root primordia initiated later, the
zone with completed cell division is relatively shorter, in the youngest primordia the non-meristematic cells may be lacking.
The root meristem is reactivated after the primary root primordium has broken through the sheath-like coleorrhiza and emerges
from the caryopsis as the primary root. The character of root meristem indicates a reduced water content at the embryonic
development of root primordium. With progressing growth the root apex becomes thinner, the meristematic region becomes longer,
and the differences in the extent of cell division between individual cell types increase. — The primary root base is formed
of cells pre-existing in the seminal root primordium. Upon desiccation of caryopsis in maturation, and subsequent quiescent
period, their development was temporarily broken, proceeding with the onset of germination. The length of this postembryonically
non-dividing basal zone is different in individual cell types. The column of central metaxylem characteristic of the smallest
number of cell cycles, has, under the given conditions, a mean length of about 22 mm, whereas the pericycle, as the tissue
with most prolonged cell division, has a mean length of about 6 mm. In the seminal root primordia initiated later the non-dividing
areas are relatively shorter. The basal region of seminal roots thus differs in its ontogenesis from the increase which is
formed “de novo” by the action of root meristem upon seed germination. 相似文献
10.
Rising atmospheric CO2 concentrations have highlighted the importance of being able to understand and predict C fluxes in plant-soil systems. We
investigated the responses of the two fluxes contributing to below-ground efflux of plant root-dependent CO2, root respiration and rhizomicrobial respiration of root exudates. Wheat (Triticum aestivum L., var. Consort) plants were grown in hydroponics at 20°C, pulse-labelled with 14CO2 and subjected to two regimes of temperature and light (12 h photoperiod or darkness at either 15°C or 25°C), to alter plant
C supply and demand. Root respiration was increased by temperature with a Q
10 of 1.6. Root exudation was, in itself, unaltered by temperature, however, it was reduced when C supply to the roots was reduced
and demand for C for respiration was increased by elevated temperature. The rate of exudation responded much more rapidly
to the restriction of C input than did respiration and was approximately four times more sensitive to the decline in C supply
than respiration. Although temporal responses of exudation and respiration were treatment dependent, at the end of the experimental
period (2 days) the relative proportion of C lost by the two processes was conserved despite differences in the magnitude
of total root C loss. Approximately 77% of total C and 67% of 14C lost from roots was accounted for by root respiration. The ratio of exudate specific activity to CO2 specific activity converged to a common value for all treatments of 2, suggesting that exudates and respired CO2were not composed of C of the same age. The results suggest that the contributions of root and rhizomicrobial respiration
to root-dependent below-ground respiration are conserved and highlight the dangers in estimating short-term respiration and
exudation only from measurements of labelled C. The differences in responses over time and in the age of C lost may ultimately
prove useful in improving estimates of root and rhizomicrobial respiration. 相似文献
11.
Meng Li Mengxue Wang Qingyun Lin Mengyao Wang Xufang Niu Jie Cheng Meizhi Xu Yaxin Qin Xinyi Liao Jian Xu Shuang Wu 《植物学报(英文版)》2022,64(4):859-870
Root cap not only protects root meristem, but also detects and transduces the signals of environmental changes to affect root development. The symplastic communication is an important way for plants to transduce signals to coordinate the development and physiology in response to the changing enviroments. However, it is unclear how the symplastic communication between root cap cells affects root growth. Here we exploit an inducible system to specifically block the symplastic communication in the root cap. Transient blockage of plasmodesmata (PD) in differentiated collumella cells severely impairs the root development in Arabidopsis, in particular in the stem cell niche and the proximal meristem. The neighboring stem cell niche is the region that is most sensitive to the disrupted symplastic communication and responds rapidly via the alteration of auxin distribution. In the later stage, the cell division in proximal meristem is inhibited, presumably due to the reduced auxin level in the root cap. Our results reveal the essential role of the differentiated collumella cells in the root cap mediated signaling system that directs root development. 相似文献
12.
After injection of the L7 dorsal root ganglion with 3H-leucine, fast axoplasmic transport carries some 3–5 × more labeled materials down the sensory fibers branches entering the sciatic nerve as compared to the dorsal root fiber branches of the neurons. Freeze-substitution preparations taken from the two sides of the lumbar seventh dorsal root ganglia of cats and monkeys showed little difference in the histograms of nerve fiber diameters of the sensory nerve fiber branch of these neurons as compared to the dorsal root fiber branches. A similar density of microtubules and of neurofilaments in the dorsal root and sensory nerve fiber branches over a wide range of fiber diameters was found in electron micrograph preparations. In the absence of an anatomical difference in the fibers to account for the asymmetrical outflow, a functional explanation based on the transport filament model was advanced. 相似文献
13.
Park S Takano Y Matsuura H Yoshihara T 《Bioscience, biotechnology, and biochemistry》2004,68(6):1366-1368
A maize plant (Zea mays) planted in a test tube was found to inhibit the growth of the soil-borne plant pathogen, Fusarium oxysporum f. sp. melongenae. The antifungal compounds, 6-methoxybenzoxazolinone and 6,7-dimethoxybenzoxazolinone, were isolated from an ethanol extract of Zea mays roots, and (6R)-7,8-dihydro-3-oxo-alpha-ionone and (6R,9R)-7,8-dihydro-3-oxo-alpha-ionol were isolated from the root exudate. 相似文献
14.
B De Rybel D Audenaert W Xuan P Overvoorde LC Strader S Kepinski R Hoye R Brisbois B Parizot S Vanneste X Liu A Gilday IA Graham L Nguyen L Jansen MF Njo D Inzé B Bartel T Beeckman 《Nature chemical biology》2012,8(9):798-805
The acquisition of water and nutrients by plant roots is a fundamental aspect of agriculture and strongly depends on root architecture. Root branching and expansion of the root system is achieved through the development of lateral roots and is to a large extent controlled by the plant hormone auxin. However, the pleiotropic effects of auxin or auxin-like molecules on root systems complicate the study of lateral root development. Here we describe a small-molecule screen in Arabidopsis thaliana that identified naxillin as what is to our knowledge the first non-auxin-like molecule that promotes root branching. By using naxillin as a chemical tool, we identified a new function for root cap-specific conversion of the auxin precursor indole-3-butyric acid into the active auxin indole-3-acetic acid and uncovered the involvement of the root cap in root branching. Delivery of an auxin precursor in peripheral tissues such as the root cap might represent an important mechanism shaping root architecture. 相似文献
15.
Loïc Pagès Valérie Serra Xavier Draye Claude Doussan Alain Pierret 《Plant and Soil》2010,328(1-2):35-44
To measure the elongation rate of individual roots in soil remains a challenge. A novel method for estimating elongation rates of excavated roots is presented. Morphological markers are identified along the tip of excavated roots, and their distance relative to the apex is measured. These markers correspond to developmental stages which follow known temporal patterns. Hence, their distance relative to the apex reflects root elongation during the period corresponding to their development. The method was tested on maize roots grown in a range of conditions and substrates. It was found that distances from markers to apices were proportional, with some variability, to elongation rates. Remarkably, the linear relationships between these distances were neither affected by substrate, nor by growing conditions. Using several markers allows covering time periods ranging from 0.3 day to 3 days as well as cross validation of estimates. Provided further testing, under a wider range of environmental conditions, is conducted, the concepts presented in this paper may serve to define a new measurement technique. 相似文献
16.
Partitioning of carbon in split root systems of barley: effect of temperature of the root 总被引:3,自引:0,他引:3
The time-course of partitioning of recently fixed photosynthateto a barley root was followed during a step change in the temperatureof the root. The induced change in partitioning had a responsetime of about 1 h, whilst the change in respiratory loss fromthe root of labelled and unlabelled CO was much faster. Theseobservations suggest that while a sudden temperature changehas an immediate effect upon the metabolic rate of the rootsit is not the metabolic rate as such which influences import(sink strength). The reported temperature responses are consistentwith the supposition that the size of the cytosolic pool ofsugar in the root, which is supplied directly by phloem importand used as a substrate for root metabolism, appears to controlimport into the root. Key words: Carbon partitioning, temperature, barley, Hordeum vulgare L., roots 相似文献
17.
植物的根系分泌物是植物根系与周围环境之间的化学媒介,通过传递特定的信息,调节根际微环境,影响周围植物的生长。玉米(Zea mays L.)和荞麦(Fagopyrum esculentum Moench)是农作物间套作体系中典型的不能搭配的组合,其障碍因素尚不清楚。以玉米为受体植物,采用根悬空培养的方法,研究了荞麦、高粱(Sorghum bicolor(L.) Moench)根系分泌物对玉米根边缘细胞和根生长的影响。结果发现,玉米根边缘细胞离体培养条件下,用荞麦根系分泌物中的小分子物质处理4、8 h显著诱导边缘细胞凋亡、死亡,细胞活率分别比对照降低了71.6%和72.3%;荞麦根系分泌物中的小分子物质对玉米根产生氧化胁迫,诱导根SOD、POD和CAT活性分别比对照高22.6%、33.9%和107.2%,根中超氧阴离子(O2-·)和脯氨酸含量分别比对照高33.9%和49.8%;荞麦根系分泌物中小分子物质的胁迫使根细胞膜透性增大,与对照相比升高80.0%,丙二醛(MDA)含量比对照升高31.5%;荞麦根系分泌物中小分子物质诱导根内源激素(IAA)含... 相似文献
18.
Branching out in new directions: the control of root architecture by lateral root formation 总被引:4,自引:0,他引:4
Plant roots are required for the acquisition of water and nutrients, for responses to abiotic and biotic signals in the soil, and to anchor the plant in the ground. Controlling plant root architecture is a fundamental part of plant development and evolution, enabling a plant to respond to changing environmental conditions and allowing plants to survive in different ecological niches. Variations in the size, shape and surface area of plant root systems are brought about largely by variations in root branching. Much is known about how root branching is controlled both by intracellular signalling pathays and by environmental signals. Here, we will review this knowledge, with particular emphasis on recent advances in the field that open new and exciting areas of research. 相似文献
19.
Origin of the epidermis in root meristems 总被引:3,自引:0,他引:3
F. A. L. CLOWES 《The New phytologist》1994,127(2):335-347
20.
Ultrastructure of the chromoplasts in the carrot root 总被引:3,自引:0,他引:3