摘要:

The histogenesis of the leaf venation inTrifolium wormskioldiiwas followed, using whole cleared leaflets and transverse and paradermal microtome sections. Mature leaflets are about 8 mm in length. The midvein precambium appears in leaflets 100μin length; secondary vein procambium is first seen in 230μleaflets; procambium of minor veins first appears in leaflets 400‐600μin length. Phloem is apparent before xylem, in midvein, secondary veins, and minor veins. Vein endings are initiated and they mature last. No evidence was found to support the theory of “vein breakage.” In the greenhouse 24 days elapsed from leaf initiation to exposure of leaf tips; 6 more days elapsed until full leaf expansion.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07247.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

A study of the pollen tube pathway inLilium leucanthumvar.centifoliumand inL. regalereveals that the entire pathway from stigma to ovule is lined with cytologically unique stigmatoid cells. Assays for chemotropic activity of tissues and exudates along the pathway of pollinated or unpollinated pistils showed that onset of chemotropic activity progressed basipetally (and, when pollinated, in advance of the pollen tubes), commencing at the stigma 3‐5 days before anthesis and appearing in the ovules 1‐2 days after anthesis. Activity persists about 10 days in ovules of pollinated pistils and for 14‐16 days in ovules of non‐pollinated pistils. Attempts to localize the source of the chemotropic factor showed that gynoecial tissues bearing stigmatoid cells are chemo‐tropically active while slices of style or ovary wall lacking stigmatoid cells are inactive. When ovules were sliced transversely and the micropylar and chalazal halves assayed, only the micropylar half showed activity. We suggest that the ovules and the stigmatoid tissue along the pollen tube pathway are the sources of the chemotropic factor responsible for the directional growth of the pollen tube.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07248.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The ultrastructure and composition of the egg and central cell ofGossypium hirsutum(cotton) was investigated. The egg is a large, highly vacuolate cell partially surrounded by a wall. This wall, which is thickest at the micropylar end of the cell, disappears approximately 2/3 of the length of the cell from the micropylar end. The chalazal 1/3 of the cell is surrounded by a plasma membrane. The egg cell shows many characteristics, both in structure and composition, of an inactive cell. No indication of the destruction or formation of cell organelles was found in the egg during the period covered in this study. The central cell is a large, highly vacuolate cell and contains the two polar nuclei. A description of the fusion of the polar nuclei through membrane fusion is given. The nuclear membranes of the polar nuclei are apparently highly active. Indeed, the entire central cell appears active. Much of this activity may be associated with the enlargement of the central cell and the breakdown of the nucellus. The differences in the metabolic condition between the egg and central cell at the time of double fertilization may influence the subsequent initial rate of development of the zygote and the endosperm.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07249.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

A comparative study was made of the ability of cultured pith tissue, leaves of buds induced from callus, and mature leaf tissue ofNicotiana tabacumL. ‘Maryland Mammoth’ to fix carbon, as determined by light‐induced C14O2incorporation. Photosynthetic ability was then correlated with the fine structure of chloroplasts from these tissues. The light to dark incorporation ratio for C14O2was at least 3 times as great in the leaf tissue as in growing cultured tissue. The chlorophyll content of the leaf tissue was 10 times as great. The carbon fixation pattern of all the tissues, as determined by radioautographs of chromatogramed extracts, was qualitatively the same. The rate of sucrose synthesis differed greatly, since 20% of the total radioactivity of the extracts from mature leaf tissue appeared in sucrose, while only 1.0% was found in sucrose from callus extracts. The incorporation of C14O2into sugars was inhibited in all the tissue by DCMU (3,4‐dichlorophenyl,1, 1‐dimethylurea). Cultured tissue past the log phase of growth was intermediate between the younger cultured tissue and the leaf tissue in its chlorophyll content and ability to incorporate C14O2in the light. Proplastids from dark‐grown callus possessed stroma lamellae, but prolamellar bodies were not observed. The chloroplasts from growing callus were partially differentiated in comparison with chloroplasts from mature leaf tissue, since each granum had only 4‐7 lamellae. Chloroplasts from callus past the log phase of growth were indistinguishable from those in mature leaves. This study establishes that the differentiation of chloroplasts in cultured tissue is a function of the growth rate of the tissue. The growth rate and degree of differentiation of the tissue can be regulated, so a well‐defined system is available for the experimental study of chloroplast differentiation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07250.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

In both the English and Algerian ivies,Hedera helixL. andHedera canariensisWilld., leaf dimorphism of the juvenile and the mature, fruiting growth phases is pronounced, the former being a vine with lobed leaves and the latter a shrubby, upright form with entire leaves. Tissue cultures of English ivy started from stems of the two growth phases on the same plant consistently behaved differently, those from the juvenile stage invariably having the higher proliferation rate and larger cells. These differences were maintained consistently in monthly transfers over a period of two years. No medium was found which would support the growth of tissue subcultures of the adult stage of Algerian ivy, but all growth phases of the English ivy were cultured freely in a modified White's medium with additions of coconut water, naphthaleneacetic acid, enzymatic casein hydrolysate, and inositol. Cultures from individual open‐pollinated seedlings of both species varied greatly in proliferation rate but were usually high.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07251.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Natural populations of the diploid species,Tragopogon dubius, T. pratensisandT. porrifolius, the F1hybrids of these species, and the two amphidiploids,T. mirusandT. miscellus, were obtained from the same localities used for previous morphological and cytological studies of the evolutionary relationships of this complex. Inter‐ and intra‐populational comparisons were made utilizing 2‐dimensional chromatograms of these taxa. Members of the complex shared a group of 18 flavonoid‐type pattern components, no one of which was completely species specific. Therefore, species patterns were expressed for a population rather than an individual with pattern components being expressed as a frequency. Patterns for F1hybrids and amphidiploids, expressed in the same manner, were relatable to the parental species. Diploid species and F1hybrid patterns were the most variable in areas of greatest sympatry, indicating considerable genetic interchange between species. The distribution of specific components in certain populations was interpreted as chemical introgression. Evidence was presented for separate origins ofT. mirusin two localities. The results confirm previous interpretations of the evolutionary relationships in this complex, and when compared to those obtained forBaptisia, they implicate the different breeding systems as important factors in establishing the kind of variation observed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07252.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Decreases in the growth and organ‐forming capacities characterized continuously cultured tobacco(Nicotiana tabacum‘Wisconsin 38‘) callus. The root‐initiation ability was completely lost in 1 1/2‐year‐old cultures. The rate of shoot formation decreased to a low plateau in cultures that reached 1 1/2‐3 years of age since the explanting. An inverse relationship between callus growth and in vitro clonal age was also observed. Studies with callus clones started from individually isolated pith cells showed that the growth and organ‐forming potentials of somatic cells varied, signifying that cell alterations had occurred in vivo. Both totipotent and non‐totipotent cell lines were obtained. Subculturing the single‐cell lines through several passages disclosed that the morphogenetically depressed state was irreversible and instability was characteristic of the totipotent lines. In the latter, a change toward the morphogenetically repressed level was observed. These findings are discussed in relation to the phenomenon of senescence. It is suggested that an accumulation of somatic mutations, i.e., genetic alterations resulting in reductions in the morphogenetic potential of cells, is a basis underlying senescence.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07253.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The direction and extent of GA transport in Pinto beans has been studied. The increase in growth rate was used as a measure of the amount of GA which reached the stem apex. The evidence showed that a similar increase in stem growth occurred whether GA was applied to the first trifoliolate leaf or to the apex of the shoot, but considerably less elongation resulted when GA was applied to primary leaves. When leaves were treated with GA after remaining in darkness for extended times, no increase in stem elongation was observed; however, growth was promoted when the plants were returned to light. The time required for a sufficient amount of GA to be translocated from the leaf to increase stem growth is less than 1 hour. The maximum growth response was found when the treated leaf was left on the plant for 3 or more hours. A study of GA movement in two‐branched plants was made. The untreated branch showed no growth response when GA was applied to the apex of the other branch, even if the dose of GA was 20 × greater than a saturating dose. Similar results were observed when GA was applied to the first trifoliolate leaf. Considerable GA moved from a mature leaf to the opposite shoot if this untreated branch had been defoliated. The pattern of GA movement to the opposite shoot was dependent on the position of the treated leaf on the shoot. It is concluded that the movement of applied GA is related to carbohydrate transport within the plant.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07254.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Five thiamine‐requiring mutants were obtained at two loci. Two are blocked in the synthesis of the pyrimidine part of the vitamin, the other three have lost the ability to make the thiazole moiety. None of the tested substances suggested as possible or likely precursors of the pyrimidine or the thiazole components of thiamine displayed any activity in the mutants. These conditional lethals responded to remarkably small supplements of thiamine. The pyrimidine‐requiring mutants utilized to some extent the anti‐vitamin neopyrithiamine. The thiazole‐less mutants grew on basal media supplemented only with the analog, oxythiamine. Thiamine deficiency, irrespective of the position of the genetic block in the synthesis, results in a characteristic anomaly of pigmentation. The position of thepylocus in the second linkage group has been determined. Allelic complementation has not been detected. The frequency of mutations affecting thiamine synthesis appears about the same inArabidopsisas in fungi. The general frequency of reparable genetic lesions is, however, one to two orders of magnitude lower inArabidopsisthan that in fungi or bacteria.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07255.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The kinetics of degradation of RNA, total protein, ribosomal and soluble (R‐S) protein and DNA were followed over 24 hours in excised segments of Kentucky Wonder pole beans (Phaseolus vulgaris). In absence of exogenous auxin, RNA degradation proceeded from about zero time. By 15 hours, after about 20% of the RNA had degraded, the degradation of DNA, total protein and R‐S protein was initiated. Exogenous auxin (25 ppm α‐napthaleneacetic acid) prevented these degradations. The addition of kinetin had little or no effect. Auxin enhanced incorporation of orotic acid into RNA two to several times more than it did amino acids into protein. Actinomycin D repressed RNA synthesis about 75% including a repression of auxin‐induced synthesis. It had no effect on the basal level of protein synthesis but did repress auxin‐induced synthesis. The results indicate that the primary action of auxin in preventing senescence of bean endocarp tissue is at the site of RNA synthesis, and the effect of auxin on DNA and protein is a consequence of the effect of auxin on RNA metabolism.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb07256.x

出版商:Wiley    

年代:1965

数据来源: WILEY