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1.
Utilization of Seed Reserves and Currently Produced Photosynthates by Embryonic Tissues of Pine Seedlings 总被引:3,自引:0,他引:3
The importance of seed reserves for growth of Pinus resinosaAit. during and shortly after seed germination was studied undercontrolled conditions. Tissues in the resting embryo were notcompletely differentiated. Many small, presumably reserve particleswere present in the embryo in addition to reserves in the megagametophyte.During seed germination, procambia in the embryo first differentiatedprotophloem 2 days after seeds were sown. The radicle beganto emerge from the seed coat at 5 days, at which time initialxylem formation was observed. Also, at approximately the sametime, primordia of primary needles were forming in the peripheralzone of the apex. Elements of the photosynthetic apparatus,including stomata and mesophyll with chloroplasts, were differentiatedfirst in the hypocotyl and then in cotyledons between 5 and8 days after seeds were sown. Photosynthetic rates of youngseedlings were correlated with rates of cotyledon expansion.During early developmental stages, reserve particles in megagametophytecells and embryo cells gradually disappeared. Surgical removalof megagametophytes at various stages of seed germination resultedin subsequent growth inhibition of the hypocotyl-radicle axis,with early removal of cotyledons suppressing most growth. Growthof primary needles appeared to be influenced indirectly by megagametophytereserves, probably by changes in amount of photosynthetic tissue.The embryo alone possessed capacity to differentiate such tissuesas primary needle primordia, stomata, and primary and secondaryvascular systems. Megagametophyte reserves appeared to contributeto growth of embryonic tissues only after the embryo itselfinitiated growth. Both current photosynthesis of seedlings andseed reserves contributed importantly to seedling development. 相似文献
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A revision of the Jurassic aphid family Genaphididae revealed that the type genus Genaphis did not have the characteristics usually attributed to this family. This discovery led to a series of taxonomic decisions. The diagnosis of the family Genaphididae is emended. The genera Aphaorus, Juraphis and Pterotella are moved to the Juraphididae, fam.n. The new family is included in the superfamily Palaeoaphidoidea. Additionally, two new species, Juraphis karataviensis sp.n. and Pterotella shartegensis sp.n. , are described. Phylogenetic relationships among the taxa of Juraphididae, the position of the family, and the distribution and palaeoecology of the taxa are discussed. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:411C1D8C‐AA45‐4311‐AA2D‐4469E44B6EDF . 相似文献
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PIOTR UCZYSKI 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2005,38(2):143-154
Eight specimens of Devonian stromatoporoids with well visible latilaminae arrangement exposed on polished slabs were subjected to a detailed morphometric analysis. The studies have revealed that the so far used stromatoporoid parameterization method leaves a broad field of uncertainty concerning the exact definitions of particular parameters. The possible ways of making the measurements and the propositions of more precise definitions of the parameters used in the method, both of the growth form above the sea bottom and of the whole skeleton are therefore presented in this paper. The Bm - basal length of the skeleton, has been defined as a straight line joining the two ends of the basal surface, which have been pointed basing on the stromatoporoid's overall shape, latilaminae arrangement and angular relation to the main growth axis position in ontogenetical development, length. The Bn - basal length of the growth form above the sea bottom, is to be measured along a straight line joining the ends of the last visible latilamina. From among a number of possible definitions of the Vm - vertical height of the whole skeleton, a straight line joining the initial growth nucleus and the highest point on the specimen's surface above the Bm line has been selected. The Vn - vertical height of the growth form above the sea bottom is defined as the height of the point on the stromatoporoid surface highest above the Bn measured perpendicularly to it. A parameter of burial ratio, BR=(Vm-Vn)/Vm, is introduced. 相似文献
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A specific color test for 17α-hydroxy, 20-keto, 21-methyl steroids is described. The reagent, vanillin in 85% phosphoric acid, is particularly useful in locating such compounds on paper chromatograms, and aids in distinguishing between 17-hydroxy, 20-keto, 21-methyl steroids, and 17-hydroxy, 20-keto, 21-hydroxy steroids. 相似文献
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PIOTR ŁUKASIK EMILY L. HANCOCK JULIA FERRARI H. CHARLES J. GODFRAY 《Ecological Entomology》2011,36(6):790-793
1. Facultative endosymbiotic bacteria of insects are known to affect life‐history traits of their hosts, and can provide important fitness benefits under certain environmental conditions. While several distinct endosymbiont‐induced effects have been reported, there is no data on whether heritable facultative endosymbionts in any species affect their hosts' performance at low temperatures, something that could have a major effect on insect physiology and survival, and thus population structure and distribution. 2. The original facultative endosymbionts were experimentally removed from five clonal genotypes of the grain aphid, Sitobion avenae Fab., which were then exposed to frost. 3. Aphid genotypes differed considerably in survival following the exposure and in fecundity of the survivors. However, the presence of the facultative symbionts had no overall effect on the studied traits. 4. The results suggest that the facultative symbionts have limited effects on the cold hardiness of their grain aphid hosts. 相似文献
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Selective predation of Esox lucius on Gasterosteus aculeatus in a natural assemblage of fish of a stream in Central Poland is described and analysed. The number of lateral plates, the standard length and four size-dependent traits were significantly smaller for sticklebacks from stomach samples than for those from population samples. Thc remaining three metric traits were not significantly different among the samples. The regressions of five metric features (out of seven) on the standard length were significantly different between the sample of caten sticklebacks and that from the free-living population. This supports the supposition that the selectivity of pikc predation with respect to metric traits is not attributable to selection on body size of the prey. Thus, it is reasonable to claim that the sample of caten sticklebacks is selectively taken from the natural population. It justifies the selective predation assumption of some hypotheses of the causes of the pattern of geographic variation in the three-spined stickleback. 相似文献