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891.
不同光强对加拿大一枝黄花生长和叶绿素荧光的影响 总被引:23,自引:1,他引:22
以外来入侵种加拿大一枝黄花(Solidago canadensis)为研究对象,在4种光照强度处理下,对其光合色素含量、叶绿素荧光特性、比叶重、植株的生长特征和生物量分配等指标进行了测定分析.结果表明:(1)随着光照强度的减弱,加拿大一枝黄花叶片的Chla、Chlb和Chl(a b)均上升,Chla/Chlb下降,4种光强处理下叶片的初始荧光(Fo)、光系统Ⅱ实际光化学效率(ФPSⅡ)、光系统Ⅱ最大光能转化效率(Fv/Fm)日变化曲线相似,高光强下的Fo、ФPSⅡ和Fv/Fm均小于中、低和弱光强下的,这说明加拿大一枝黄花能适应较大的光强幅度,同时对低、弱光强有一定的抗逆性.(2)生长在高(RI为100%)、中(RI为60%)光强下的加拿大一枝黄花植株正常生长,生长于低(RI为20%)弱(RI为5%)光强下的植株生长不良,表现为植株矮小,茎秆细弱.中度的遮荫对它的生长没有明显影响,但在严重遮阴下生长受抑.(3)生长在高、中光强下的总生物量、地下部分生物量明显增多,低、弱光强处理下的叶生物量比显著增加.结果表明,加拿大一枝黄花在高、中光强下对生长最有利,能够适应较大幅度的光照变化,但在严重遮阴下生长明显受抑,说明该入侵植物不易入侵到密林等光照强度比较弱的生境. 相似文献
892.
Wen F Celoy RM Nguyen T Zeng W Keegstra K Immerzeel P Pauly M Hawes MC 《Plant cell reports》2008,27(7):1125-1135
Mitosis and cell wall synthesis in the legume root cap meristem can be induced and synchronized by the nondestructive removal of border cells from the cap periphery. Newly synthesized cells can be examined microscopically as they differentiate progressively during cap development, and ultimately detach as a new population of border cells. This system was used to demonstrate that Pisum sativum L. fucosyl transferase (PsFut1) mRNA expression is strongly expressed in root meristematic tissues, and is induced >2-fold during a 5-h period when mitosis in the root cap meristem is increased. Expression of PsFut1 antisense mRNA in pea hairy roots under the control of the CaMV35S promoter, which exhibits meristem localized expression in pea root caps, resulted in a 50-60% reduction in meristem localized endogenous PsFut1 mRNA expression measured using whole mount in situ hybridization. Changes in gross levels of cell wall fucosylated xyloglucan were not detected, but altered surface localization patterns were detected using whole mount immunolocalization with CCRC-M1, an antibody that recognizes fucosylated xyloglucan. Emerging hairy roots expressing antisense PsFut1 mRNA appeared normal macroscopically but scanning electron microscopy of tissues with altered CCRC-M1 localization patterns revealed wrinkled, collapsed cell surfaces. As individual border cells separated from the cap periphery, cell death occurred in correlation with extrusion of cellular contents through breaks in the wall. 相似文献
893.
894.
Masoomeh Etehadnia Doug Waterer Hielke De Jong Karen K. Tanino 《Journal of Plant Growth Regulation》2008,27(2):125-140
Tolerance of salt stress in potato (Solanum tuberosum L.) increased when the plants were pre-exposed to low concentrations of salt (salt acclimation). This acclimation was accompanied
by increased levels of abscisic acid (ABA) in the shoot. To further study the role of roots and shoots in this acclimation
process, reciprocal grafts were made between a salt-tolerant (9506) and salt-sensitive ABA(−) mutant and its ABA(+) normal
sibling potato genotype. The grafted plants were acclimated with 75 or 100 mM NaCl for 3 weeks and then exposed to 150–180 mM
NaCl, depending on the salt tolerance of the rootstock. After 2 weeks of exposure to the salt stress, the acclimated and unacclimated
plants were compared for physiologic and morphologic parameters. The response to the salt stress was strongly influenced by
the rootstock. The salt-tolerant 9506 rootstock increased the salt tolerance of scions of both the ABA-deficient mutant and
its ABA(+) sibling. This salt tolerance induced by the rootstock was primarily modulated by salt acclimation and manifested
in the scion via increased plant water content, stem diameter, dry matter accumulation, stomatal conductivity, and osmotic
potential, and is associated with a reduction in leaf necrosis. There was also a pronounced scion effect on the rootstock.
Using 9506 as a scion significantly increased root fresh and dry weights, stem diameter, and root water content of ABA(−)
mutant rootstocks. Specific evidence was found of the role of exogenous ABA in the enhancement of water status in grafted
plants under salt stress beyond that of grafting alone. This was verified by more positive stomatal conductivity and upward
water flow in ABA-treated grafted and nongrafted plants and the absence of upward water flow in nontreated grafted plants
through NMR imaging. Grafting using either salt-tolerant scions or rootstocks with inherently high ABA levels may positively
modify subsequent responses of the plant under salt stress. 相似文献
895.
Root tensile strength and root distribution of typical Mediterranean plant species and their contribution to soil shear strength 总被引:13,自引:0,他引:13
S. De Baets J. Poesen B. Reubens K. Wemans J. De Baerdemaeker B. Muys 《Plant and Soil》2008,305(1-2):207-226
In Mediterranean environments, gully erosion is responsible for large soil losses. It has since long been recognized that
slopes under vegetation are much more resistant to soil erosion processes compared to bare soils and improve slope stability.
Planting or preserving vegetation in areas vulnerable to erosion is therefore considered to be a very effective soil erosion
control measure. Re-vegetation strategies for erosion control rely in most cases on the effects of the above-ground biomass
in reducing water erosion rates, whereas the role of the below-ground biomass is often neglected or underestimated. While
the above-ground biomass can temporally disappear in semi-arid environments, roots may still be present underground and play
an important role in protecting the topsoil from being eroded. In order to evaluate the potential of plant species growing
in Mediterranean environments to prevent shallow mass movements on gully or terrace walls, the root reinforcement effect of
25 typical Mediterranean matorral species (i.e. shrubs, grasses herbs, small trees) was assessed, using the simple perpendicular
model of Wu et al. (Can Geotech J 16:19–33, 1979). As little information is available on Mediterranean plant root characteristics,
root distribution data were collected in SE-Spain and root tensile strength tests were conducted in the laboratory. The power
root tensile strength–root diameter relationships depend on plant species. The results show that the shrubs Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. have the strongest roots, followed by the grass Brachypodium retusum (Pers.) Beauv. The shrubs Nerium oleander L. and the grass Avenula bromoides (Gouan) H. Scholz have the weakest roots in tension. Root area ratio for the 0–0.1 m topsoil ranges from 0.08% for the grass
Piptatherum miliaceum (L.) Coss to 0.8% for the tree Tamarix canariensis Willd. The rush Juncus acutus L. provides the maximum soil reinforcement to the topsoil by its roots (i.e. 304 kPa). Grasses also increase soil shear strength
significantly (up to 244 kPa in the 0–0.1 m topsoil for Brachypodium retusum (Pers.) Beauv.). The shrubs Retama sphaerocarpa (L.) Boiss. and Anthyllis cytisoides L. are increasing soil shear strength to a large extent as well (up to 134 and 160 kPa respectively in the 0–0.10 m topsoil).
Whereas grasses and the rush Juncus acutus L. increase soil shear strength in the topsoil (0–0.10 m) to a large extent, the shrubs Anthyllis cytisoides (L.), Retama sphaerocarpa (L.) Boiss., Salsola genistoides Juss. Ex Poir. and Atriplex halimus L. strongly reinforce the soil to a greater depth (0–0.5 m). As other studies reported that Wu’s model overestimates root
cohesion values, reported root cohesion values in this study are maximum values. Nevertheless, the calculated cohesion values
are used to rank species according to their potential to reinforce the soil. 相似文献
896.
The chilling injury induced by high root temperature in the leaves of rice seedlings 总被引:2,自引:0,他引:2
Root temperature is found to be a very important factor forleaves to alter the response and susceptibility to chillingstress. Severe visible damage was observed in the most activeleaves of seedlings of a japonica rice (Oryza sativa cv. Akitakomachi),e.g. the third leaf at the third-leaf stage, after the treatmentwhere only leaves but not roots were chilled (L/H). On the otherhand, no visible damage was observed after the treatment whereboth leaves and roots were chilled simultaneously (L/L). Thechilling injury induced by L/H, a novel type of chilling injury,required the light either during or after the chilling in orderto develop the visible symptoms such as leaf bleaching and tissuenecrosis. Chlorophyll fluorescence parameters measured aftervarious lengths of chilling treatments showed that significantchanges were induced before the visible injury. The effectivequantum yield and photochemical quenching of PSII dropped dramaticallywithin 24 h in both the presence and absence of a 12 h lightperiod. The maximal quantum yield and non-photochemical quenchingof PSII decreased significantly only in the presence of light.On the other hand, L/H chilling did not affect the functionof PSI, but caused a significant decrease in the electron availabilityfor PSI. These results suggest that the leaf chilling with highroot temperature destroys some component between PSII and PSIwithout the aid of light, which causes the over-reduction ofPSII in the light, and thereby the visible injury is inducedonly in the light. 相似文献
897.
Genotypic variation in seedling root architectural traits and implications for drought adaptation in wheat (Triticum aestivum L.) 总被引:1,自引:0,他引:1
Ahmad M. Manschadi Graeme L. Hammer John T. Christopher Peter deVoil 《Plant and Soil》2008,303(1-2):115-129
Root system characteristics are of fundamental importance to soil exploration and below-ground resource acquisition. Root
architectural traits determine the in situ space-filling properties of a root system or root architecture. The growth angle
of root axes is a principal component of root system architecture that has been strongly associated with acquisition efficiency
in many crop species. The aims of this study were to examine the extent of genotypic variability for the growth angle and
number of seminal roots in 27 current Australian and 3 CIMMYT wheat (Triticum aestivum L.) genotypes, and to quantify using fractal analysis the root system architecture of a subset of wheat genotypes contrasting
in drought tolerance and seminal root characteristics. The growth angle and number of seminal roots showed significant genotypic
variation among the wheat genotypes with values ranging from 36 to 56 (degrees) and 3 to 5 (plant−1), respectively. Cluster analysis of wheat genotypes based on similarity in their seminal root characteristics resulted in
four groups. The group composition reflected to some extent the genetic background and environmental adaptation of genotypes.
Wheat cultivars grown widely in the Mediterranean environments of southern and western Australia generally had wider growth
angle and lower number of seminal axes. In contrast, cultivars with superior performance on deep clay soils in the northern
cropping region, such as SeriM82, Baxter, Babax, and Dharwar Dry exhibited a narrower angle of seminal axes. The wheat genotypes
also showed significant variation in fractal dimension (D). The D values calculated for the individual segments of each root system suggested that, compared to the standard cultivar Hartog,
the drought-tolerant genotypes adapted to the northern region tended to distribute relatively more roots in the soil volume
directly underneath the plant. These findings suggest that wheat root system architecture is closely linked to the angle of
seminal root axes at the seedling stage. The implications of genotypic variation in the seminal root characteristics and fractal
dimension for specific adaptation to drought environment types are discussed with emphasis on the possible exploitation of
root architectural traits in breeding for improved wheat cultivars for water-limited environments. 相似文献
898.
Elevated levels of many metals are toxic to plant roots, but their modes of action are not well understood. We investigated
the toxicities of aluminium (Al), copper (Cu), and lanthanum (La) in solution on the growth and external morphology of 3-d-old
cowpea (Vigna unguiculata L.) roots for periods of up to 48 h. Root elongation rate decreased by 50% at ca. 30 μM Al, 0.3 μM Cu, or 2.0 μM La, accompanied
by a decrease in the distance from the root tip to the proximal lateral root. Kinks developed in some roots 2.0 ± 0.4 mm from
the root apex on exposure to Al or La (but not Cu). Light and scanning electron microscopy showed that soluble Al, Cu, or
La caused similar transverse ruptures to develop > 1 mm from the root apex through the breaking and separation of the rhizodermis
and outer cortex from inner-layers. The metals differed, however, in the range in concentration at which they had this effect;
developing in solutions containing 54 to‑600 μM Al, but only from 0.85 to 1.8 μM Cu or 2.0 to 5.5 μM La. These findings suggest
that Al, Cu, and La bind to the walls of cells, causing increased cell wall rigidity and eventual cell rupturing of the rhizodermis
and outer cortex in the elongating zone. We propose that this is a major toxic effect of Al, and that Cu and La also have
additional toxic effects. 相似文献
899.
900.
Role of aluminum-binding ligands in aluminum resistance of Eucalyptus camaldulensis and Melaleuca cajuputi 总被引:1,自引:0,他引:1
We investigated the roles of Al-binding ligands in Al exclusion from roots and in internal Al detoxification in roots as Al
resistance mechanisms in two Al-resistant Myrtaceae trees, Eucalyptus camaldulensis Dehnh. and Melaleuca cajuputi Powell. The amounts of ligands secreted from roots and contained in root tips of these species were compared with those of
an Al-sensitive species, Melaleuca bracteata F. Muell., after the roots were exposed to 0 or 1 mM AlCl3 solution. Secretion of well-known ligands (citrate, oxalate, and malate) from roots under Al treatment was low in all species.
However, in E. camaldulensis, the Al-binding capacity of root exudates under Al treatment was considerable and was higher than that in M. bracteata. Gel filtration chromatography revealed that a low-molecular-weight Al-binding ligand was secreted from roots in response
to Al only in E. camaldulensis. On the other hand, the Al-binding capacity of cell sap in root tips under Al treatment was similar for the resistant and
sensitive species. These results suggest that Al exclusion by secretion of the unknown low-molecular-weight Al-binding ligand
from roots contributes to the Al resistance of E. camaldulensis, whereas M. cajuputi has developed Al-resistance mechanisms other than secretion of ligands from roots or concentration of internal ligands in
root tips. 相似文献