摘要:

AbstractThe neotropical treesChorisia chodatii, C. speciosa, Tabebuia caraibaandT. ochraceashow late‐acting self‐incompatibility. Accumulated ovule penetrations following self‐pollinations were similar to those in crosses. During the six to eight day period following pollination, in both selfed and crossed ovules, a resting zygote with initial development of the endosperm was formed. Up until the time of rejection of the selfed flowers, no cytological malfunctions were evident in the selfed o

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00339.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe wild type (WT) ofScenedesmus obliquusand a mutant lacking chlorophyll b and the light‐harvesting complexes (WT‐LHC1) were synchronized by a light‐dark regime. Both cultures contained the same type of carotenoids. However, concentrations and patterns of carotenoids were different during their synchronous life cycles. The concentration of total carotenoids followed more or less that of chlorophyll. The WT contained more carotenoids per cell mass, but slightly less per chlorophyll. It is discussed that part of the carotenoids of the mutant, lacking the peripheral antenna of PSII, might be located in the chlorophyll b‐less apoprotein or in an enlarged core antenna of PSII.During the life cycle ofScenedesmusthe carotenes are initially synthesized and most of the α‐carotene is immediately oxidized to lutein which is inserted in the antennae systems of PSII and PSI. The further oxidation of lutein to loroxanthin seems to depend on both the change from dark to light, and on stages of the life cycle itself. Although the major part of β‐carotene appears to be inserted in the reaction centers, a fraction of the total pool is rapidly converted to violaxanthin, following the onset of illumination. The conversion may serve to protect against photooxidation. Further conversion of violaxanthin to neoxanthin occurs to a greater extent in the mutant, WT‐LHC1. The results demonstrate (1) the close connection between the carotenoid pattern and the modulation of the photosynthetic apparatus during the life cycle ofScenedesmusand (2) the flexibility of the organism in compensating for the absence of the light‐harvesting complexes of photosystems II by adjusting the carote

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00340.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe photosynthetic performance of macroalgae isolated in Antarctica was studied in the laboratory. Species investigated were the brown algaeHimantothallus grandifolius, Desmarestia anceps, Ascoseira mirabilis, the red algaePalmaria decipiens, Iridaea cordata, Gigartina skottsbergii, and the green algaeEnteromorpha bulbosa, Acrosiphonia arcta, Ulothrix subflaccidaandU. implexa. Unialgal cultures of the brown and red algae were maintained at 0°C, the green algae were cultivated at 10°C. IKvalues were between 18 and 53 μmol m−2s−1characteristic or low light adapted algae. Only the twoUlothrixspecies showed higher IKvalues between 70 and 74 μmol m−2s−1. Photosynthesis compensated dark respiration at very low photon fluence rates between 1.6 and 10.6 μmol m−2s−1. Values of α were high: between 0.4 and 1.1 μmol O2g−1FW h−1(μmol m−2s−1)−1in the brown and red algae and between 2.1 and 4.9 μmol O2g−1FW h−1(μmol m−2s−1)−1in the green algal species. At 0°C Pmaxvalues of the brown and red algae ranged from 6.8 to 19.1 μmol O2g−1FW h−1and were similarly high or higher than those of comparable Arctic‐cold temperate species. Optimum temperatures for photosynthesis were 5 to 10°C inA. mirabilis, 10°C inH. grandifolius, 15°C inG. skottsbergiiand 20°C or higher inD. ancepsandI. cordata. P: R ratios strongly decreased in most brown and red algae with increasing temperatures due to different Q10values for photosynthesis (1.4 to 2.5) and dark respiration (2.5 to 4.1). These features indicate considerable physiological adaptation to the prevailing low light conditions and temperatures of Antarctic waters. In this respect the lower depth distribution limits and the northern distribution boundaries of these species partly

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00341.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractFollowing a taxonomic revision ofNectandra, a genus of about 114 species of neotropical trees, character gradients are compared against geographical distribution, habitat preferences, and reproductive phenology of individual species, with the aim of reconstructing the spatial and temporal diversification of the genus. It is shown thatNectandra, together withOcotea, Persea, and other genera of the Lauraceae, originated from a northern hemisphere matrix that immigrated into South America, perhaps as late as after the closure of the Central American land bridge in the Pliocene. The dramatic diversification of the genus within South America was facilitated by its ornithochorous dispersal system, implying ample processes of allopatric speciation. At present, speciation seems to take place preferably by processes of ecotypic (mostly edaphic) specialization, by which widely distributed, ecologically polymorphic species give rise to swarms of ecologically narrowly specialized satellite species.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00342.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractDark grown hypocotyl protoplasts fromHelianthus annuusL. cvs. Cerflor and Euroflor were electrically fused to produce somatic hybrids. Following fusion, the protoplasts were cultivated in agarose droplets for four weeks. Macroscopic visible calli (0.1‐0.3 mm) were transferred onto solid medium and calli reaching a size of 3 mm were collected. Their isoenzyme patterns were analysed based on two different isoenzymes that allow discrimination between the two cultivars used for fusion. From the examined calli, about 26 % showed an isoenzyme pattern of putative binary heterokaryocytes. The isoenzyme pattern of the non‐fused control revealed less than 5% of possibly chimeric colon

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00343.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY