摘要:

SUMMARYThe ovule primordia ofRuta, Zanthoxylum, andSkimmiaare trizonate. The initiation and further development of the ovule in the three genera is rather similar, but inRutaandZanthoxylumthe outer integument is of dermal origin whereas inSkimmiait is partly also of subdermal derivation. The mature seed coats vary appreciably in structure, which may be explained by the different dispersal mechanisms of the fruits or seeds.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb00243.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYDespite the great differences in type of seed dispersal and seed structure,LiriodendronandMagnoliashow similarity in their ovule ontogeny and in the early phases of seed development. The ovule primordium is 3‐zonate; the inner integument is dermal, and the outer integument subdermal in origin. The cells of the inner epidermis of the outer integument may undergo periclinal divisions and differentiate into a sclerotic layer. However, the outer epidermis and the subdermal tissue of the outer integument inLiriodendronare not multiplicative and do not differentiate into a fleshy, coloured sarcotesta as inMagnolia, but undergo sclerification.This study is in agreement with Dandy's (1964) subdivision of the family and supports the generally held view thatLiriodendronis the most advanced member of the Magnoliaceae.It is posed that the 3‐zonate ovule primordium is basic in angiosperms. This clashes with the classical carpel concept, in which the carpel is interpreted as a metamorphosed leaf bearing ovules on its margins or on the adaxial surface of its lam

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb00244.x

年代:1977

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb00245.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYAn attempt was made to explain the influence of stylar age on the growth of compatible pollen tubes based on peroxidase data.The growth of compatible pollen tubes inNicotiana alatastyles varied with the physiological age of the style. Especially in detached styles ageing caused changes by which the tube growth was retarded, or even totally inhibited. One of these changes might be the increase in the activity of several stylar peroxidase isoenzymes. Among them, there was the isoenzyme 10 which has previously been suggested to be involved in the inhibition of the growth of incompatible pollen tubes. The senescence‐induced increase in the activity of this isoenzyme in unpollinated styles was 3 to 4 times higher when the styles were detached from the flower.Anin situextraction of walls and intercellular material by centrifugation after vacuum infiltration of stylar sections revealed that after ageing during 7 days, the detached styles contained 9 times more extracellular peroxidase 10 than the styles which remained attached to the flower.A possible relationship between peroxidase release from cytoplasm to walls and intercellular spaces, and inhibition of pollen tube growth was discusse

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb00246.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe chromosome number of 118 plants belonging to 108 species collected in the wild in Syria has been determined. Notes on some species are given.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb00247.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe adaptability ofCirsium palustre, a shade avoiding species, andGeum urbanum, a species avoiding exposed conditions in the ash coppice cycle, to a change from a high to a low light intensity was studied, in order to simulate the changes taking place in the light climate in a deciduous woodland in spring. Both the vegetative rosette phase and the generative phase were considered. In the rosette phase a rapid adaptation to the low light intensity took place in both species in a similar way. In the generative phaseGeumadapted much better after the plants had been transferred from a high to a low light intensity. The dry weight increase ofCirsiumceased after the transfer, whereasGeumcontinued to grow. The leaf area ratio was much higher after the transfer, giving better assimilation in limiting light conditions.Cirsiumwhen continuously grown in a low light intensity also had a high leaf area ratio, but the stems were too weak to support themselves, in contrast withGeum. So in the vegetative phase both species can be considered shade tolerant, butCirsium palustreis not shade tolerant in the generative phase.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb00248.x

年代:1977

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb00249.x

年代:1977

数据来源: WILEY