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221.
Faustino Menegus Liliana Cattaruzza Leonardo Scaglioni Enzio Ragg 《Physiologia plantarum》1992,86(1):168-172
Seeds of the water plant Trapa natans L. (water chestnut) can germinate in strict anoxia. The seedlings show seminal roots growing upwards while shoot buds remain quiescent until O2 becomes available. Trapa seedlings are highly tolerant to anoxia. The rate of ethanol fermentation was 21.2 μmol (g FW)−1 h−1 , while production of lactate was negligible and lower than that of succinate. The seminal root of Trapa compares better to the rice coleoptile rather than to the rice root, both functionally and as to the metabolic response to anoxia. The anaerobic germination of Nuphar luteum L. and Scirpus mucronatus L. was also characterized by a limited developmental program. 相似文献
222.
The distribution of NO3? reduction between roots and shoots was studied in hydro-ponically-grown peach-tree seedlings (Prunus persica L.) during recovery from N starvation. Uptake, translocation and reduction of NO3?, together with transport through xylem and phloem of the newly reduced N were estimated, using 15N labellings, in intact plants supplied for 90 h with 0.5 mM NH4+ and 0.5, 1.5 or 10 mM NO3?. Xylem transport of NO3? was further investigated by xylem sap analysis in a similar experiment. The roots were the main site of NO3? reduction at all 3 levels of NO3? nutrition. However, the contribution of the shoots to the whole plant NO3? reduction increased with increasing external NO3? availability. This contribution was estimated to be 20, 23 and 42% of the total assimilation at 0.5, 1.5 and 10 mM NO3?, respectively. Both 15N results and xylem sap analysis confirmed that this trend was due to an enhancement of NO3? translocation from roots to shoots. It is proposed that the lack of NO3? export to the shoots at low NO3? uptake rate resulted from a competition between NO3? reduction in the root epidermis/cortex and NO3? diffusion to the stele. On the other hand, net xylem transport of newly reduced N was very efficient since ca 70% of the amino acids synthesized in the roots were translocated to the shoots, regardless of the level of NO3? nutrition. This net xylem transport by far exceeded the net downward phloem transport of the reduced N assimilated in shoots. As a consequence, the reduced N resulting from NO3? assimilation, principally occurring in the roots, was mainly incorporated in the shoots. 相似文献
223.
The influence of nicotianamine (NA) on formation and elongation of adventitious roots in hypocotyls of de-rooted NA-less mutant seedlings of Lycopersicon esculentum Mill, was examined in relation to the iron supply [ferric N-N'-ethylenediaminedi-(2-hydroxyphenylacetate) (FEDDHA), ferric ethylenediaminetetracetate (FeEDTA), ferric N-(2-hydroxyethyl)-ethylenediaminetriacetate (FeHEDTA, Fe-citrate and FeCl3 ] in the nutrient solution. The initiation of root primordia in hypocotyl cuttings was independent of NA and occurred with about the same frequency in both, mutant and wild-type. In the mutant the development of primordia to adventitious roots was blocked at all iron sources used, except FeEDTA. Addition of NA (5x 10−6 to 2 × 10−5 M ) to the rooting medium resulted in a fast growth of adventitious roots in mutant cuttings with all iron sources tested. Rooting of wild-type cuttings was independent from NA application and iron sources. We suppose that NA is involved in the intracellular transport of iron. Its function is possibly linked with chelation of ferrous iron in the cell. 相似文献
224.
Effects of phosphate availability on the root system architecture: large-scale analysis of the natural variation between Arabidopsis accessions 总被引:3,自引:1,他引:3
F. CHEVALIER M. PATA P. NACRY P. DOUMAS & M. ROSSIGNOL 《Plant, cell & environment》2003,26(11):1839-1850
Developmental plasticity is one main adaptative response of plants to the availability of nutrients. In the present study, the naturally occurring variation existing in Arabidopsis for the growth responses to phosphate availability was investigated. Initially details of the effects of phosphate starvation for the four currently used accessions Cvi, Col, Ler and Ws were compared. A set of 10 growth parameters, concerning the aerial part and the root system, was measured in both single‐point and time‐course experiments. The length of the primary root and the number of laterals were found to be consistently reduced by phosphate starvation in all four accessions. These two robust parameters were selected to further screen a set of 73 accessions originating from a wide range of habitats. One‐half of the accessions showed also a reduced primary root and less lateral roots when phosphate‐starved, and 25% were not responsive to phosphate availability. For the last quarter of accessions, phosphate starvation was found to affect only one of the two growth parameters, indicating the occurrence of different adaptative strategies. These accessions appear to offer new tools to investigate the molecular basis of the corresponding growth responses to phosphate availability. 相似文献
225.
Horacio Paz 《Biotropica》2003,35(3):318-332
I analyzed patterns of variation in root mass allocation and root morphology among seedlings of woody species in relation to environmental factors in four Neotropical forests. Among forests, I explored the response of root traits to sites varying in water or nutrient availability. Within each forest, I explored the plastic response of species to different microhabitats: gaps and understory. Additionally, I explored evidence for life history correlation of root and shoot traits by comparing species differing in their successional group (light‐demanding [22 spp.] or shade tolerant [27 spp.]) and germination type (species with photosynthetic cotyledons or species with reserve cotyledons). At each forest site, young seedlings from 10 to 20 species were excavated. A total of 55 species was collected in understory conditions and 31 of them were also collected in gaps. From each seedling, six morphological ratios were determined. Allocation to roots was higher in forest sites with the lowest soil resources. Roots were finer and longer in the most infertile site, while roots were deeper in the site with the longest dry season. Seedling traits did not differ between germination types. Shade tolerant species allocated more to roots and developed thicker roots than light‐demanding species. Light‐demanding species showed stronger plastic responses to habitat than shade tolerant species, and species with photo‐synthetic cotyledons showed lower plasticity than species with reserve cotyledons. Overall, these results suggest that among Neotropical species, root allocation and root morphology of seedlings reflect plant adjustments to water or nutrient availability at geographic and microhabitat scales. In addition, life history specialization to light environments is suggested by differences among groups of species in their allocation to roots and in their root morphology. 相似文献
226.
冬小麦根表面氧化还原活力的研究 总被引:4,自引:1,他引:3
证实了两个不同品种的冬小麦根系表面存在着氧化NADH和还原K3Fe(CN)6的氧化的活力。还原铁氰化物活力在PH5.5到8.5范围内随着PH值升高而增大,温度在15℃到45℃范围内随温度升高还原活力增强,45℃达最高值,55℃时活力急剧下降。 相似文献
227.
228.
Abstract. We studied floristic and diversity patterns and their environmental controls in two landscapes of contrasting topography in the Patagonian steppe. The analyses were focused on the effects of water availability gradients and landscape configuration on plant species distribution and coexistence. Floristic variation was investigated using Correspondence Analysis. The relationship between floristic and environmental variation was analyzed using Canonical Correspondence Analysis and correlation tests. We explored diversity patterns by relating spatial distance to floristic dissimilarities. The floristic gradient was determined by shrub and grass species and was related to precipitation in the flat area, and to precipitation, elevation and potential radiation in the mountain area. Site species richness increased with water availability in both areas. Mean site species richness and species turnover in space was higher in the mountain than in the flat area. Landscape species richness and floristic gradients were more concentrated in the mountain than in the flat area. In contrast to shrubs and grasses, forb species distributions were uncoordinated and probably independent of any environmental gradient. Our results suggest (1) that landscape configuration affects species composition and diversity through its direct effect on abiotic environmental heterogeneity, and (2) that the environmental controls of the community composition vary depending on the plant functional type considered. 相似文献
229.
230.