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81.
Endosperm development was studied in normally setting flowersand pods of soybean from anthesis to a pod length of 1020mm. The free-nuclear stage following double fertilization istypified by loss of starch and increasing vacuolation. The cytoplasmprovides evidence of extensive metabolic activity. Wall ingrowths,already present at the micropylar end of the embryo sac wallprior to fertilization, develop along the lateral wall of thecentral cell as well as at the chalazal endosperm haustorium.Endosperm cellularization begins when the embryo has developeda distinct globular embryo proper and suspensor. Cellularizationstarts at the micropylar end of the embryo sac as a series ofantidinal walls projecting into the endosperm cytoplasm fromthe wall of the central cell. The free, growing ends of thesewalls are associated with vesicles, microtubules, and endoplasrnicreticulum. Pendinal walls that complete the compartmentalizalionof portions of the endosperm cytoplasm are initiated as cellplates formed during continued mitosis of the endosperm nuclei.Endosperm cell walls are traversed by plasmodesmata. This studywill provide a basis for comparison with endosperin from soybeanflowers programmed to abscise. Glycine max, soybean, endosperm, ovules 相似文献
82.
C. C. J. CULVENOR J. A. EDGAR L. W. SMITH M. V. JAGO J. E. PETERSON 《Nature: New biology》1971,229(8):255-256
WHEN she reported the chronic hepatotoxicity of the alkaloids senkirkine and hydroxysenkirkine, which are esters of the aminoalcohol otonecine, Schoental1 suggested that 1,2-epoxides rather than pyrrolic derivatives2,3 are the active metabolites of hepatotoxic pyrrolizidine alkaloids. We have results which confirm the hepatotoxicity of otonecine esters but argue against the suggested involvement of 1,2-epoxides. 相似文献
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85.
JON M. ERLANDSON TODD J. BRAJE TORBEN C. RICK JENNA PETERSON 《American anthropologist》2005,107(4):677-683
Terminal Pleistocene and Early Holocene sites on California's Channel Islands provide evidence for early maritime activity, including the use of seaworthy boats. Numerous early shell middens have been identified, but specific information on the maritime peoples who occupied them is limited. Our research at CA-SMI-608, a roughly 9,500-year-old shell midden on San Miguel Island, produced a relatively large assemblage of bifaces and other chipped stone artifacts, shell beads, worked bone, and well-preserved faunal remains. Food remains are dominated by mussels, abalones, and other shellfish from the rocky intertidal, but fish, sea mammal, and sea bird remains were also recovered. These data provide a detailed view of early maritime activities along an arid coastline previously considered marginal to human settlement. 相似文献
86.
A. TOWNSEND PETERSON 《Biological journal of the Linnean Society. Linnean Society of London》1992,47(3):249-260
The effects of philopatry on levels of genetic differentiation were examined in the Aphelocoma jays through comparisons of gray-breasted jays (A. ultramarina; highly philopatric) and scrub jays (A. coerulescens; dispersing). Gray-breasted jays breed cooperatively in groups of up to 25 individuals, with individuals typically breeding either on the natal territory or on adjacent territories. Western North American scrub jays breed in non-cooperative pairs, with individuals typically dispersing at least 0.5 km, and often much farther. Genetic differentiation among six populations in northern Mexico and the south-western United States in each of the species was compared using starch-gel electrophoresis of protein products of 29 presumptive genetic loci. Strong differences in levels of genetic differentiation exist between the two species, both when measured using F-statistics and in terms of the slope of the isolation by distance relationship. These results suggest that social systems involving high degrees of philopatry may lead to considerably elevated rates of genetic differentiation and speciation. 相似文献
87.
CAROL A. PETERSON CHRISTOPHER J. PERUMALLA 《Botanical journal of the Linnean Society. Linnean Society of London》1990,103(2):113-125
PETERSON, C. A. & PERUMALLA, C. J., 1990. A survey of angiosperm species to detect hypodermal Casparian bands. II. Roots with a multiseriate hypodermis or epidermis.
Roots of 25 species which had either a multiseriate hypodermis or a multiseriate epidermis were tested for the presence of a hypodermal Casparian band. All species save one were in the Liliopsida and six were orchids with both soil and aerial roots. Lignosuberized hypodermal Casparian bands were present in all species tested; those with a biseriate hypodermis had bands in both layers and of those with a multiseriate hypodermis, the three species which were tested had bands in every layer. Although Casparian bands can often be recognized by the presence of sinuous walls in longitudinal views of uniseriate hypodermal layers, these sinuosities were not evident in multiseriate hypodermal layers containing Casparian bands. The lack of air spaces, once thought to be a characteristic feature of the hypodermis, did not hold true for some members of the Liliopsida. All walls of the hypodermis were suberized, indicating that suberin lamellae were probably present in addition to Casparian bands. We recommend using the term 'exodermis' to refer to a hypodermis which has a Casparian band. Epidermal walls of non-orchid roots were suberized whereas those of orchids were lignified. Regardless of their type of modification, all epidermal walls were permeable to the apoplastic dye, Cellufluor. 相似文献
Roots of 25 species which had either a multiseriate hypodermis or a multiseriate epidermis were tested for the presence of a hypodermal Casparian band. All species save one were in the Liliopsida and six were orchids with both soil and aerial roots. Lignosuberized hypodermal Casparian bands were present in all species tested; those with a biseriate hypodermis had bands in both layers and of those with a multiseriate hypodermis, the three species which were tested had bands in every layer. Although Casparian bands can often be recognized by the presence of sinuous walls in longitudinal views of uniseriate hypodermal layers, these sinuosities were not evident in multiseriate hypodermal layers containing Casparian bands. The lack of air spaces, once thought to be a characteristic feature of the hypodermis, did not hold true for some members of the Liliopsida. All walls of the hypodermis were suberized, indicating that suberin lamellae were probably present in addition to Casparian bands. We recommend using the term 'exodermis' to refer to a hypodermis which has a Casparian band. Epidermal walls of non-orchid roots were suberized whereas those of orchids were lignified. Regardless of their type of modification, all epidermal walls were permeable to the apoplastic dye, Cellufluor. 相似文献
88.
Cultures of 12 South African isolates of an undescribedFusarium species resembling but distinct fromF camptoceras were analysed for the presence of diacetoxyscirpenol (DAS), neosolaniol monoacetate (NMA), and T-2 toxin, by capillary gas chromatography utilizing electron capture detection. No DAS or T-2 toxin could be detected in any of the cultures of the isolates. NMA was, however, detected in 10 of the 12 isolates at levels ranging from 310 to 2060 ng/g. The method used, was primarily developed for the determination of DAS and T-2 toxin in fungal cultures and grain samples but was found to be suitable for the coextraction of NMA at an average recovery of 80.8%, with a detection limit in the order of 100 ng/g. Supportive evidence for the presence of the NMA was obtained by capillary gas chromatography / mass spectrometry. Regarded as a relatively rare trichothecene, NMA has never been reported to occur naturally and has previously been shown to be produced by only a fewFusarium strains. 相似文献
89.
90.
AMINO ACID SELECTION IN PROTEIN BIOSYNTHESIS 总被引:10,自引:0,他引:10
P. J. PETERSON 《Biological reviews of the Cambridge Philosophical Society》1967,42(4):552-610