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1.
The rooting of softwood cuttings of Alnus incana (L.) Moench in nutrient solution was studied under controlled conditions. Cuttings consisting of one internode with the leaf and axillary bud attached rooted easily and more rapidly than shoot tip cuttings. Light was necessary for rooting but good rooting was obtained in photon flux densities of both 40 and 190 μmol m-2s-1. Root number and root length was reduced when light reached the base of the cuttings. Treatment with indolebutyric acid (10-6–10-4M) increased the number of roots but 10-4M delayed rooting and decreased the root length. Debudded internode cuttings rooted as well as intact cuttings, and detached leaves also contained sufficient substances for rooting. 相似文献
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HANS RYBERG LENNART AXELSSON KARL-OLOF WIDELL HEMMING I. VIRGIN 《Physiologia plantarum》1980,49(4):431-436
Abstract When dark grown leaves of wheat (Triticum aesivum L.) were given a brief irradiation, there was an immediate onset of chlorophyll (Chl) b synthesis in the dark. This synthesis led to a rather slow accumulation of Chl b, which ceased when the Chl b/Chl a ratio had reached a value of about 0.1. The Chl b synthesis occurred also when the seedlings were treated with the herbicide SAN 9789. Leaves grown under different intensities of red light accumulated Chl b and Chl a, resulting in a ratio Chl b/Chl a which depended on the light intensity. If the light intensity was low, Chl a accumulated to a level about ten times the level of PChlide of the dark grown leaves. This occurred without any increase in the Chl b/Chl a ratio. There was no difference between SAN 9789-treated seedlings and water controls in this respect. Above a certain threshold of irradiance, the Chl b/Chl a ratio in the control leaves increased rapidly with the irradiation intensity. The increase in Chl b/Chl a ratio coincided with formation of grana in the plastids. This increase was not found and grana formation was completely absent in the seedlings treated with SAN 9789. The possibility of two different stages in the Chl b synthesis is discussed. 相似文献
4.
Young seedlings of Picea abies Karst, grown in nutrient solution were treated with the growth retardants Amo-1618, B-995, and CCC. These were added to the nutrient medium. B-995 and CCC retarded root and shoot growth in the concentrations 100, 10, and 1 mg/l. Growth was almost entirely inhibited by 300 mg/l, obviously due to toxicity. The effects of Amo-1618 were similar but more varying. GA counteracted the effects of all the retardants on shoot growth, but not on root growth. 相似文献
5.
LENNART AXELSSON 《Physiologia plantarum》1974,31(2):77-85
Dark-grown leaves of wheat fed with δ-aminolevulinic acid accumulate protochlorophyllide636 in excess. After the leaves had been illuminated with high intensity red light (154 W × m?2) for half a minute, a treatment which blocks the phototrans-formation protochlorophyllide chlorophyllide, the sensitivity of chlorophyllide and protochlorophyllide to light was examined. The decrease in pigment content, caused by photo-oxidation was found to be very close to a second order reaction. The second order “rate constant” for decrease in absorbance was found to be eight times greater for the formed chlorophyllide than for protochlorophyllide. The light intensity dependence of the decomposition was found to be linear within the intensity range used (E= 25 – 154 W × m?2). In samples in which the pigments had been heat denatured, it was possible to photodecompose the chlorophyllide without affecting the protochlorophyllide. The results are discussed in connection with the theory of a photodynamic action involving oxygen in the singlet state (1ΔO2). 相似文献
6.
LENNART JEPPSSON 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1986,19(1):66-66
Eldredge, N. & Stanley, S. M. (eds.) 1984: Living Fossils. (Casehooks in Earth Sciences; series Editor R. N. Ginsburg.) 相似文献
7.
JENS ANDERSSON PÄR BYSTRÖM LENNART PERSSON ANDRE M. DE ROOS 《Biological journal of the Linnean Society. Linnean Society of London》2005,85(3):341-351
Resource polymorphism has been suggested to be a platform for speciation. In some cases resource polymorphism depends on phenotypic plasticity but in other cases on genetic differences between morphotypes, which in turn has been suggested to be the ongoing development of a species pair. Here we study environmentally induced morphological differences in two age classes of Arctic char ( Salvelinus alpinus ) influencing char performance and diet in relation to resource availability. We found that structurally complex habitats with relatively lower zooplankton densities gave rise to individuals with a deeper body, and a downward positioned tip of the snout compared with individuals from structurally simple habitats with relatively higher zooplankton densities for both age classes. Environment also had an effect on foraging efficiency on zooplankton, with fish from structurally simple habitats had a higher foraging rate than fish from structurally complex habitats. Diet analyses showed that resource use in char mainly depends on the relative abundance of different resources. Therefore, to gain further understanding of resource polymorphism we suggest that future studies must include population dynamic feedbacks by the resources on the consumers. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 341–351. 相似文献
8.
Light effects on root formation in aspen and willow cuttings 总被引:1,自引:0,他引:1
The effect of light on rooting of leafy cuttings of aspen (Populus tremula × tremuloides) and a willow hybrid (Salix caprea × viminalis) was investigated under controlled conditions in water culture. Two levels of irradiance were used, 40 and 8 W m?2. The lower level gave the best rooting of aspen cuttings, both when applied to the stock plants before the cuttings were taken and when given to the cuttings during the rooting period. Irradiation of the cutting base during the rooting period inhibited rooting almost completely in aspen and decreased the number of roots formed in the Salix hybrid. Net photosynthesis in the cuttings of Salix decreased considerably after excision and increased again after formation of roots. Indirect evidence indicated that photosynthesis was even more affected in aspen cuttings. The possible roles of carbohydrates and inhibitors in the light effects are discussed. 相似文献
9.
White light increases the inhibition of growth in length of pea seedling roots caused by 2,4-D. This effect is most pronounced in the case of lateral root growth. The effect is obtained also if the shoots above the cotyledons are removed and is probably due to the direct influence of light on the roots. While light also weakly enhances the inhibition of pea root growth caused by 1-naphthylacetic acid, light does not increase the sensitivity of wheat roots to 2,4-D or naphthylacetic acid. 相似文献
10.