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1.
I. G. Burns 《Plant and Soil》1992,142(2):221-233
A method is described for determining the way in which growth rate varies with plant nutrient concentration using a simple
nutrient interruption technique incorporating only 2 treatments. The method involves measuring the changes in growth and nutrient
composition of otherwise well-nourished plants after the supply of one particular nutrient has been withheld. Critical concentrations
are estimated from the relationship between the growth rate (expressed as a fraction of that for control plants of the same
size which remained well-nourished throughout) and the concentration of the growth-limiting nutrient in the plants as deficiency
developed. Trials of the method using young lettuce plants showed that shoot growth rate was directly proportional to total
N (nitrate plus organic N) concentration, and linearly or near-linearly related to K and P concentration over a wide range;
the corresponding relationship for nitrate was strongly curvi-linear. Critical concentrations (corresponding to a 10% reduction
in growth rate) determined from these results were similar to critical values calculated from models derived from field data,
but were generally higher than published estimates of critical concentration (based on reductions in shoot weight) for plants
of a similar size. Reasons for these discrepancies are discussed. Nitrate, phosphate or potassium concentrations in sap from
individual leaf petioles were highly sensitive to changes in shoot growth rate as deficiency developed, with the slope of
the relationships varying with leaf position, due to differences both in their initial concentration and in the rates at which
they were utilized in individual leaves. Each nutrient was always depleted more quickly in younger leaves than in older ones,
providing earlier evidence of deficiency for diagnostic purposes. Although the plants were capable of accumulating nitrate,
phosphate and potassium well in excess of that needed for optimum dry matter production during periods of adequate supply,
the rate of mobilization of these reserves was insufficient to prevent reductions in growth rate as the plants became deficient.
This brings into question the validity of the conventional concept that luxury consumption provides a store of nutrients which
are freely available for use in times of shortage. The implications of these results for the use of plant analysis for assessing
plant nutrient status are discussed. 相似文献
2.
3.
Identification of fossil leaf impressions as Cercis has been questioned based upon the presence or absence of a pulvinus at the base of the lamina (upper pulvinus). In the present study, leaves of Cercis canadensis were examined before and after abscission to explore the degradation processes that could occur prior to fossilization, and the North American record for fossil foliage of Cercis was revised accordingly. Results for C. canadensis indicate that: (1) the pulvinus consists largely of tissues with nonlignified cells (a wide cortex, a nonlignified fiber sheath, phloem, and pith) that degrade rapidly after leaf abscission, (2) the lignified xylem tissue that remains in the pulvinus after degradation is in brittle strands, (3) the pulvinus degrades at a faster rate than the lamina or the petiole, and (4) the degraded pulvinus cushion leaves a semicircular pattern on the lamina. From examination of fossils as well as extant species, we: (1) demonstrated that in fossils, the upper pulvinus can show a greater degree of degradation than the adjoining petiole or lamina tissue, suggesting the degradation of upper pulvinus tissue is similar in modern vs. fossil specimens, (2) defined numerous other laminar characters that can be used in conjunction with, or in the absence of, an upper pulvinus to confirm the presence of Cercis in the fossil record, and (3) showed from those criteria that the earliest known North American fossil leaf record for Cercis, from a specimen newly reported in the present study, is from the middle Miocene Succor Creek flora of Oregon. 相似文献
4.
Simonetta Pancaldi A. Bonora Rita Gualandri R. Gerdol R. Manservigi Maria Palmira Fasulo 《Plant biology (Stuttgart, Germany)》1998,111(4):261-272
Abstract: Laminae and petioles from mature winter leaves of Arum italicum were studied in order to obtain information on the sun—shade intra-tissue properties of chloroplasts. This inference was based on the: (1) micro- and submicroscopic characteristics of the chloroplasts, (2) cytochemical localizations of functional PS I and PS II, (3) pigment patterns and compositions, (4) immunolocalization of Rubisco, and (5) net photosynthesis. It was inferred that all the chloroplasts across the lamina had adaptations to intermediate shade conditions, without a sun-shade dimorphism between the palisade and the spongy tissues. In the petiole, where normally-structured chloroplasts were surprisingly present in the entire thickness of the organ, a structural and chemical dimorphism was found between the outer chlorenchyma and the inner aerenchyma where intermediate shade-type and extreme shade-type chloroplasts were present, respectively. However, some anomalies in the pigment composition were noted chiefly in the inner aerenchyma (low concentrations of β-carotene and lutein, absence of zeaxanthin, presence of unusual pigments, for instance lutein epoxide, lutein cis-isomer, and chlorophyllide a). The Rubisco immunolabelling in the outer chlorenchyma of the petiole was similar to that in the lamina, while it was very scant in the inner aerenchyma. Net photosynthesis in the petiole was about 75% of that recorded in the lamina. These data suggest that the petiole of the mature winter leaf of A. italicum closely co-operates with the lamina for enhancing light capture and utilization. 相似文献
5.
Direct Delivery of Inoculum to Shoot Tissue Interferes with Genotypic Resistance to Ralstonia solanacearum in Tomato Seedlings
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Pious Thomas Avverahally T. Sadashiva Reshmi Upreti Mohammed M. Mujawar 《Journal of Phytopathology》2015,163(4):320-323
Employing known susceptible and resistant genotypes and pure bacterial inoculum (0.1 OD; 108 CFU/ml?1), five different inoculation methods were tried to assess the response of tomato genotypes to Ralstonia solanacearum. This included seed‐soaking inoculation, seed‐sowing followed by inoculum drenching, or at 2‐week stage through petiole‐excision inoculation, soaking of planting medium with inoculum either directly or after imparting seedling root‐injury. Seed‐based inoculations or mere inoculum drenching at 2 weeks did not induce much disease in seedlings. Petiole inoculation induced 90–100% mortality in susceptible checks but also 50–60% mortality in normally resistant genotypes within 7–10 days. Root‐injury inoculation at 2‐week seedling stage appeared the best for early and clearer distinction between resistant and susceptible lines. The observations suggest a role played by the root system in governing genotypic resistance to the pathogen. Direct shoot inoculation is to be adopted only for selecting highly resistant lines or to thin down segregating populations during resistance breeding. 相似文献
6.
Mohammed Arifullah Chiruvella Kishore K. Namsa Nima D. Ghanta Rama Gopal 《Physiology and Molecular Biology of Plants》2015,21(3):417-424
Physiology and Molecular Biology of Plants - Bixa orellana L. (Bixaceae) is a multipurpose tree grown for the production of commercially important dyes. In the present study, an efficient,... 相似文献
7.
Using a new experimental set up, the way in which height growth of stoloniferous plants is adjusted to that of their neighbours, as well as differences between genotypes in their ability to keep up with neighbour height growth were tested. Five Potentilla reptans genotypes inherently differing in petiole length were subjected to three experimental light gradients, involving light intensity and red : far-red ratio. Each plant was placed in a vertically adjustable cylinder of green foil, and the treatments differed in the speed of cylinder height increase and final height. Total weight of plants decreased from the 'Slow' to the 'Fast' treatment, while petiole length increased. Leaves reaching the top of the cylinder stopped petiole elongation, resulting in similar final heights for all genotypes in the 'Slow' treatment. In the 'Fast' treatment only the fastest-growing genotype maintained its position in the top of the cylinder and genotypes differed strongly in final height within the cylinders. Plants adjust their height growth to that of the surrounding vegetation, leading to height convergence in short light gradients that slowly increase. These adjustments and genotypic differences in ability to keep up with fast-growing neighbours can influence the outcome of competition for light. 相似文献
8.
9.
Igual José M. Valverde Angel Rivas Raúl Mateos Pedro F. Rodríguez-Barrueco C. Martínez-Molina Eustoquio Cervantes Emilio Velázquez Encarna 《Plant and Soil》2003,254(1):115-123
Submergence stimulates elongation of the leaves of Rumex palustris and under laboratory conditions the maximum final leaf length (of plants up to 7 weeks old) was obtained within a 9 day period. This elongation response, mainly determined by petiole elongation, depends on the availability of storage compounds and developmental stage of a leaf. A starch accumulating tap root and mature leaves and petioles were found to supply elongating leaves with substrates for polysaccharide synthesis in expanding cell walls. Changes in the composition of cell wall polysaccharides of elongated petioles suggest a substantial cell wall metabolism during cell extension. Reduced starch levels or removal of mature leaves caused a substantial limitation of submerged leaf growth. From the 5th leaf onward enough reserves were available to perform submerged leaf growth from early developmental stages. Very young petioles had a limited capacity to elongate. In slightly older petioles submergence resulted in the longest final leaf lengths and these values gradually decreased when submergence was started at more mature developmental stages. Submerged leaf growth is mainly a matter of petiole elongation in which cell elongation has a concurrent synthesis of xylem elements in the vascular tissue. Mature petioles still elongated (when submerged) by cell and tissue elongation only: the annular tracheary elements stretched enabling up to 70% petiole elongation. 相似文献
10.
Gapper Nigel E. McKenzie Marian J. Christey Mary C. Braun Robert H. Coupe Simon A. Lill Ross E. Jameson Paula E. 《Plant Cell, Tissue and Organ Culture》2002,70(1):41-50
Broccoli (Brassica oleracea var. italica) deteriorates rapidly following harvest. Postharvest treatment of broccoli with 6-benzylaminopurine delays senescence, whilst exogenous ethylene has been shown to accelerate this process following harvest. To alter ethylene biosynthesis, broccoli was transformed, using Agrobacterium tumefaciens-mediated transformation, with an antisense ACC oxidase gene from broccoli driven by the asparagine synthetase promoter from asparagus. In addition, broccoli was transformed with the chimeric gene construct SAG12-IPT to alter cytokinin biosynthesis during harvest-induced senescence. Transformation was achieved using both hypocotyl and cotyledonary petiole explants. The presence of an antisense ACC oxidase gene enhanced transformation efficiency, but Ag+ incorporated into the medium did not. The transgenic nature of these plants was confirmed by PCR and Southern analyses. 相似文献