摘要:

SUMMARYMeasurements were made of the spectral maximum, the intensity, and fading of the auto‐fluorescence spectrum during microsporogenesis and of pollen after some chemical treatments inGasteria, Pinus, Physostegia, and some other plants.Mainly the sporopollenin of the sexine and the footlayer of the pollen wall showed auto‐fluorescence which appeared to be specific for each pollen species. The cytoplasm showed sometimes autofluorescence during the initiation of the pollen wall formation. The spectral maximum increased in wave‐length and the percentage of fading decreased before the formation of the intine, but also when the intine of the pollen wall is removed.The exine of the pollen wall ofPinusdisappeared gradually after treatment with a mixture of acetic acid and hydrogen peroxyde. The pollen wall ofGasteriashowed a higher resistance to the chemical treatments compared withPinusp

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00742.x

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe morphological changes in the nucleus and cell organelles ofGasteriaduring the development of the pollen mother cell into the ripe pollen are described and discussed. From the tetrad stage till after the first mitotic division the plastids contain electron transparent granules. The number of cristae in the mitochondria increases after the first mitotic division.When the pollen wall is formed the excretion of the Golgi vesicles' content and the contact of the plasma membrane with the callose wall determine the template of the pollen wall pattern. The formation of the material for the bacula, followed by that of the tectum, and finally by that for the footlayer, takes place on the plasma membrane. The excretion of the fine fibrillar content of the Golgi vesicles proceeds till after the formation of the footlayer. The excreted material remains between the bacula.The quantitative approach revealed that during meiosis the number of cell organelles remains constant. However, an increase in number takes place first after the pollen mother cell stage and before leptotene, secondly after the first mitotic division.The data are compared with the previous results obtained withPinus sylvestrisWillemse 1971a, b, c).

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00743.x

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe vessels in the secondary xylem ofFraxinus excelsior, while running through the wood in a longitudinal direction, show a tangentially and radially curved course. Vessels are in contact over widely differing distances. The result is a rather loose three‐dimensional vascular network. The phenomena are discussed from an ontogenetical point of view, in relation to prevailing concepts of cambial activit

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00744.x

年代:1972

数据来源: WILEY

摘要:

SUMMARYIn the Netherlands two ecotypes ofSonchus arvensisL. are found: var.arvensis(arable type) on arable land and var.maritimusG. F. W. Mey. (coastal type) in coastal dunes. The author's experiments show that these differ in their response to temperature and moisture during germination.The coastal type germinates faster than the arable type and its germination occurs already at lower temperatures. Furthermore the coastal type germinates at lower moisture tensions.From these experiments it appears that the coastal type is better adapted to the germination conditions prevailing in the dune habitat. The germination characteristics of the arable type fit in well with its natural distribution pattern.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00745.x

年代:1972

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00746.x

年代:1972

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00747.x

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe circumnutation of intact and decapitatedAvenacoleoptiles is not influenced by indole‐acetic acid in whatever concentration it is added. This supports the hypothesis that circumnutation is a purely autonomous movement, unconnected with geotropism.The nutative movements inconveniently interfere with induced movements. A way of dealing with them when determining a geotropic curvature is discussed on the basis of relevant dat

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00748.x

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe influence of the culture medium on the explants of Jerusalem artichoke was studied.The concentration of the growth substances in the medium was 1 ppm IAA and NAA and 0.1 ppm 2,4‐D. Moreover, labelled auxins were added: IAA‐1‐14C, IAA‐2‐14C, (IAA‐2)‐14C, NAA‐1‐14C and 2,4‐D‐1‐14C.Eight hours extraction of the tissue by methanol at 4°C using a magnetic stirrer gave the best results. It was proved that the growth substances were absorbed and fixed in the tissue as whole molecules. The quantity of the fixed degraded molecule was not significant.One hour after absorbing the IAA the substance was incorporated into the tissue. It took 2–3 hours before NAA was incorporated and 48 hours before 2,4‐D was fixed. This proves that in the tissue an adaptation process had to take place before the auxin could be incorporated.The next problem to be studied is how the incorporated substance will be used after transfer of the tissu

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00749.x

年代:1972

数据来源: WILEY

摘要:

SUMMARYIn phosphate deficientLemna minorphotosynthesis is decreased. The plants show a rapid increase in photosynthesis upon P‐supply, often not only at saturating light intensities, but also at rate limiting intensities. The reactivation at light limitation is larger in white light than in far red, and as far as monochromatic light has been studied, larger at 650 nm than at 700, 711 and 717 nm, which probably depends on a stronger inhibition of photosynthesis at shorter wavelengths. The results are interpreted as demonstrating an effect of the P‐level on electron transport to and from photosystem I, in which the coupling to photophosphorylation and a switch from cyclic to pseudocyclic photophosphorylation may be invol

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00750.x

年代:1972

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1972.tb00751.x

年代:1972

数据来源: WILEY