摘要:

Seeds were sown on mineral agar and grown under axenic constant conditions. Floral transition and flower primordia were observed at approximately 172 and 220 hr, respectively. The vegetative apex was flat in outline for 160 hr, after which time it was slightly dome shaped; cytohistological zonation was not readily apparent. The inflorescence apex (172 hr) was markedly convex and possessed 3–5 and 4–6 cell layers in the most axial and lateral portions of the apex, respectively. The nucleoli of cells of the T2layer were larger than cells of the T1and outer corpus during vegetative development; in contrast, they were equal in size at reproductive stages.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06818.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Excised embryos of barley were cultured on a synthetic medium and their growth rate was determined to be at least equal to that of natural embryos in vivo. Embryos, 0.4 mm when excised, averaged 3.5 mm in length after 10 days’ culture. Morphogenetically, the development of cultured embryos and proembryos (0.15–0.25 mm) duplicated normal embryogenesis. Some embryos continued to grow in culture and became up to 4.5 times larger than natural embryos, but most of the increase was due to scutellar overgrowth. Proembryos of 0.1 mm length or less did not follow normal development patterns but formed protocorm‐like embryos with several shoots and roots. It is suggested that embryonic form in barley may be determined in later stages of proembryonic growth, since earlier proembryos exhibited morphogenetic plasticity in culture.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06819.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

There are 4 genotypic classes of pairings basic to the tetrapolar, or bifactorial, mating system of the BasidiomyceteSchizophyllum commune.One class has a complex phenotype termed “common‐Aheterokaryosis.” Analysis shows a high nuclear ratio to be characteristic of this heterokaryon. Selection of the majority type is independent of input nuclear ratio. The common‐Aphenotype is interpreted from old and new data to include several major traits: (1) absence of nuclear pairing and conjugate division; (2) extreme variation of nuclear ratio; (3) absence of clamp connections; (4) depression of growth, as measured by rate and final amount dry weight; and (5) usual absence of fruiting. The absence of non‐allelic complementation, previously described as part of the phenotype, has been discounted by new results. The possibility of a quantitative effect of incompatibility remains undecided.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06820.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Seed germination ofMelampyrum lineareDesr. requires activation (20 C storage or treatment with gibberellic acid) followed by an extended period of exposure to cold. Without these conditions seeds remain dormant. Seed structure and pattern of development following activation are described. Aseptic culture of embryos excised from dormant seeds showed growth to be possible on agar containing glucose but not on agar containing potato starch. Embryos excised from gibberellin‐activated seeds or embryos growing on agar containing gibberellin grew at the same rate on glucose but could not grow on starch. Thus the gibberellin‐sensitive dormancy mechanism does not involve synthesis or activation in the embryo of starch‐digesting enzymes. This could mean that such a mechanism is located in the endosperm or that the mechanism inMelampyrumis different from that described for barley and for oats

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06821.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Experiments were conducted to determine the interrelationship between the flowering ofCuscuta campestrisYuncker, a species of the parasitic angiosperm dodder, and the flowering of the short‐day plantsXanthium pennsylvanicumandGlycine maxvar.Biloxiand the long‐day plantsMatricaria parthenoidesandHyoscyamus niger.It was found that dodder flowered only on the host plants which were themselves flowering. The flowering pattern of the host plant appeared to be unaffected by the parasitism of dodder. When nonflowering dodder was introduced to soybean plants which were under noninductive photoperiods, neither dodder nor soybean flowered; but when the soybean plants were then completely defoliated, the dodder on 7 of 9 host plants began to flower. This result indicated the possibility that under noninductive photoperiods the leaves of the host plant produced a substance which inhibited the flowering of the dodder. Other experiments involved the use of soybean plants which had been linked together with bridges of living dodder. One member of each soybean pair was kept on inductive short photoperiods while the other member was kept on noninductive long photoperiods. No transmission of a flowering hormone from the induced member of each pair through the dodder bridges to the noninduced member of the pair could be demonstrated. The results, instead, support the concept that a flowering‐hormone inhibitor is translocated from the noninduced soybean partner to the induced soybean partner via the dodder bridges since the induced partners show a definitely weaker flowering pattern than corresponding photoinduced control plants.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06822.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The effect of presowing, gamma‐irradiation treatments on the growth and respiration of germinating corn was investigated. Exposures of 40 and 80 krads caused marked inhibition in seedling growth and inhibited the rate of respiration, measured as oxygen uptake per seedling. A decrease in respiration rates, at these doses, could be detected within 1 day after planting, well before emergence of the radicle. Lower doses which were not markedly growth‐inhibiting did not appear to inhibit respiration. A highly significant correlation was found between respiration rates at 1 day and shoot lengths of 3‐day‐old seedlings. The degree of correlation so measured was higher for shoots than for roots and was lowered by growth‐inhibiting doses of irradiation. The results indicate that rates of respiration during the first stages of germination may be an important factor in subsequent seedling growth and may provide the basis for predicting the growth of the shoot.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06823.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Coiled initials embedded in a stroma develop into multicellular, multinucleate ascogonia. Hyphae grow up around the ascogonia to form a prosenchymatous perithecial wall. As the ascocarp develops, an apical meristem produces cells that elongate downward into the centrum, forming long filaments, the apical paraphyses. The ascogonium produces multinucleate ascogenous cells which form a basal layer in the centrum. The ascogenous cells produce asci that grow up among the apical paraphyses, which disintegrate as the ascocarp matures. The asci are unitunicate, with a simple thickened cap punctuated by a pore. This pattern of development is typical of theNectria‐type.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06824.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

In wheat, lateral (branch) roots originate always in the pericycle of the parent root between protoxylem poles of 2 successive xylem ridges and facing a sieve tube. Although the endodermis also contributes to the initial lateral protuberance when lateral root primordia develop close to the parent root apex, the pericycle alone gives rise to the lateral root which subsequently develops. Before initiation of lateral root primordia the pericycle and endodermis are each uniseriate. The first cell divisions that are characteristic of the initiation of lateral root primordia are periclinal divisions in the pericycle. When wheat is germinated and grown on colchicine, mitosis is not completed and hence no nuclear and cell divisions occur (i.e., “c‐mitoses,” but no true mitoses, occur). Within the primary roots of these seedlings appear structures, here called “primordiomorphs,” having the shape of lateral root primordia. Each primordiomorph, which develops without cell division, is a radial protuberance in the pericycle accompanied by an associated protuberance of the adjacent endodermis. Primordiomorphs are found only between protoxylem poles of 2 successive xylem ridges and facing a sieve tube. In primordiomorphs some nuclei repeatedly enter, but none complete, mitosis. The primordiomorphs become large enough to compress the cortical parenchyma and make bulges in the epidermis of the parent root. In typical lateral root primordia comparable in size with primordiomorphs, hundreds of cell divisions have occurred that, are absent in the primordiomorphs. After removal of colchicine the primordiomorphs develop with normal cell divisions into polyploid lateral roots as shown by the following findings: (1) Stages of development are detected that are intermediate between primordiomorphs and polyploid lateral roots with typical histological organization. As in normal lateral root initiation close to the parent root apex, the endodermis contributes to the initial protuberance but the pericycle alone gives rise to the lateral root which subsequently develops. (2) The number of these polyploid lateral roots formed can be accounted for by the number of primordiomorphs which disappear. (3) No “c‐mitoses” occur, i.e., the diploid and polyploid nuclei undergo only normal mitoses. Thus, primordiomorphs have 2 definitive morphological characteristics of typical lateral root primordia, viz.: (1) precise identity of histological site of origin, and (2) potentiality (realized after removal of colchicine) to develop into roots having typical histological organization. It is, therefore, concluded that primordiomorphs are lateral root primordia that developed without completion of mitosis and without cytokinesis. Since the parent root pericycle remains uniseriate, even in that region which comprises the primordiomorph, no periclinal cell divisions within the pericycle could have altered the polarization of growth to set up the apical‐basal axis of the primordiomorph. These results demonstrate that the earliest detectable changes in form involved in the initiation of a lateral root primordium can occur without completion of any mitosis and without any cytokinesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06825.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

A chromatographic investigation of the native growth substances active on theAvenafirst‐internode test has shown the existence of at least five different peaks of activity in methanolic extracts of a short‐day and a long‐dayNicotiana, N. tabacumcultivar ‘Maryland Mammoth’ andN. sylvestris.Some of these substances are active on the dwarf‐maize test for gibberellins. The levels of the various substances have been determined in the adult leaf, the immature leaf, and the tip of the shoot. Their variations have been followed during the shifting of the plants from a noninductive to an inductive photoperiod in relation to the transition of the terminal apex from the vegetative to the reproductive state.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06826.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Upward translocation of methyl violet and P32in sporophores ofLentinus tigrinusoccurred primarily in morphologically specialized hyphae in the center of the stipes. Hyphae in which most of the translocation occurred were loosely arranged, unbranched and seldom septate as contrasted to short, densely packed hyphae in the cortical zone of the stipes where little translocation occurred. More P82was translocated in a high‐transpiration environment than in a low‐transpiration environment. Nearly all translocation was stopped by killing the sporophores with propylene oxide, even though high‐transpiration conditions were maintained. The respiratory rate of hyphae in the central zone of the stipe was greater than that of hyphae in the cortical zone.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06827.x

出版商:Wiley    

年代:1965

数据来源: WILEY