摘要:

One‐mm‐thick cortical explants excised aseptically from 10‐11 mm behind the tip of 3‐day‐old roots of the garden pea,Pisum sativum, cv. ‘Little Marvel’ were cultured on a synthetic nutrient medium supplemented with auxin or auxin and cytokinin. Nuclear DNA contents were measured in cells of the explants at the outset and at specified times during culture up to seven days. Fixed and sectioned preparations were stained with the Feulgen method using the DNA‐specific dye auramin‐O. Fluorescent microspectro‐photometric measurements of individual nuclei were made from each cortical population. At day zero all cortical nuclei measured were either 2c or 4c with respect to their DNA content. In the presence of the auxins, indoleacetic acid and 2,4‐dichlorophenoxyacetic acid, and the cytokinin, kinetin, DNA values increased to multiples of the 2c level with populations at the 8c and 16c level predominating after three days of culture as well as at seven days. In the presence of auxins alone no change in DNA values was observed during three days. Kinetin concentrations as low as 0.01 ppm were already effective. The data are interpreted to show that cytokinin, in the presence of auxin, induces two rounds of DNA synthesis prior to the first mitoses, the first round being connected with chromosome doubling by endoreduplication and the second one with normal mitosis. From this we inferred that tetraploid cells in leguminous root nodules might have arisen in the same way, i.e., by endoreduplication prior to the first mitoses induced by the rhizobial division stimulus, unless the chromosome number of root cortical cells had already been doubled by endoreduplication in the normally differentiating root systems.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05929.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The promotion of perithecial initials in the imperfect fungusMonacrosporium doedycoidesis enhanced by the addition of the RNA synthesis inhibitor 6‐methyl purine (6‐MP). The addition of two other RNA inhibitors (8‐azaguanine and actinomycin‐D) causes the promotion of initials but not at the magnitude observed with 6‐MP. Application of a protein synthesis inhibitor (cycloheximide), a base analog (5‐fluorouracil), or an amino acid analog (p‐fluorophenyl‐alanine) are not promotive on initial formation and can be inhibitory. The apparent cause for the promotion of perithecial initials in the imperfect fungus is that sexual structures are inhibited by mRNA's synthesized by the organism and the addition of 6‐MP prohibits their synthesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05930.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Protoplasts were prepared from cultured cells ofAmmi visnaga(Umbelliferae) by enzymatic digestion of the cell walls and examined microscopically. Staining of fresh protoplasts with Calcofluor and silver hexamine demonstrated the apparent absence of wall material. Protoplasts contained more cell organelles than the whole cells, particularly endoplasmic reticulum and associated polysomes. The plasmalemma of most protoplasts appeared smooth; some protoplasts were connected by structures resembling plasmodesmata. Multinucleates resulting from fusion were frequently observed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05931.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Protonemata ofLygodium japonicumturn biplanar in both red and blue light regimes and remain filamentous in far‐red light. Biplanar gametophytes formed in red light are longer than broad with long, rectangular cells, whereas in blue light they appear broader than long with short, isodiametric cells. Transfer of protonemata of all ages from far‐red regime to red or blue light induces a morphological type of growth characteristic of the new light regime. However, only relatively young biplanar forms transferred from red or blue light are able to resume filamentous type of growth in a subsequent regime of far‐red light.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05932.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The application of a new clearing technique proved successful for the study of ovule development, megasporogenesis, and megagametogenesis inCornus asperifoliaMichaux., C.strictaLam., C.amomumMiller,C. floridaL., and C.alternifoliaL. These were the first studies of embryological features inC. asperifoliaandC. stricta. Consistent features for both species include: slightly crassinucellate nucelli, megaspore mother cells, and equal dyads with the upper member obliquely aligned to the parietal cell. Alignment of nucelli of the 4‐nucleate megagametophyte is not the same for both species. More than one mature 8‐nucleate megagametophyte per nucellus was recorded forC. asperifolia. Embryological features not revealed in previous investigations of the other three species include: equal dyad cells for C.alternifoliaandC. amomum, although disintegration of defunct megaspores is variable for both species; vacuole formation at the micropylar end at the 2‐nucleate stage of C.amomum;a 4‐nucleate stage in C.amomumandC. alternifoliawith different alignments of nuclei; synergids that disintegrate rapidly in both species although antipodal shapes vary for each; and fusion of polar nuclei at varying locations within different species. A prominent hypostase is formed in all five species. Because of embryological features, it is recommended thatC. foridabe separated from the genusCornus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05933.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

A microscopic survey of the achlorophylus plantMonotropa unijloraL. reveals an ectendotrophic mycorrhizal fungus with dolipore septa associated with the roots. Special transfer regions are found in the root cell wall ensheathing all but the ruptured tip of the fungal intrusion.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05934.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Conidiogenous cells of both the synnematous and mononematous conidiophores inCeratocystis ulmiandC. piceaedevelop by sympodial proliferation. Holoblastic conidia are produced on nodules or short denticles from the synnematous conidiogenous cells and on well‐defined denticles from the mononematous conidiogenous cells.Graphium penicillioidesis characterized by percurrent proliferation of the conidiogenous cells and the conidia are holoblastic and annellidic. A comparison of the type material ofG. penicillioideswith the lectotype specimen ofC. piceaeindicates thatG. penicillioidesis not the conidial state ofC. piceae. The method of conidial development inC. ulmiandC. piceaeis distinct from that ofG. penicillioides, the lectotype species ofGraphium;these conidial states are, therefore, placed in a new hyphomycete genus,Pesotum, as thePesotumstate ofCeratocystis ulmiandC. piceae, respectively.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05935.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The genusPsilopeziais treated in a restricted sense, limited to three species.Psilopeziais characterized by its flat, appressed apothecia, large ascospores, non‐amyloid asci, and bent or deformed paraphyses. The relationship betweenPsilopeziaandPachyellais discussed. Species are distinguished by the presence or absence of gel in the apothecium, anatomy of the apothecium, size of the apothecium, and by ascospore size. Descriptions, illustrations, and a key are provided for the included species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05936.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Ibykagen. n. is described from late Middle Devonian compressions and petrifactions collected in eastern New York State. It is a robust plant of which three orders of branching and ultimate appendages (leaves) are known. The latter dichotomize up to five times, are arranged spirally on all orders of branching, are three‐dimensional, and all orders are terete in cross section. Fertile appendages, homologous with the sterile, are terminated by sporangia. The protostele has five or six arms, the maturation is mesarch, and the protoxylem disintegrates leaving lacunae at the tips of the arms. Traces to appendages are terete and arise spirally from the tips of the arms. The primary xylem consists of tracheids only, the phloem of thin‐walled cells and probable tanniniferous cells. The cortex consists of parenchyma and groups of sclereids. Secondary xylem is lacking.Ibykais placed in a new order, Ibykales, close to the Hyeniales (protoarticulates) and to the Pseudosporochnales all three of which probably evolved from Trimerophytina.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05937.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The nutritional requirements for ovule formation inNigella salivaL. were investigated by growing excised pistils on defined media. Pistils grown on a medium containing the minerals of Murashige and Skoog produced significantly more ovules than on a medium containing the minerals of Bilderback. When the nitrogen, sulfate, and phosphate of the Bilderback medium were adjusted to levels comparable to those of the Murashige and Skoog medium, a similar number of ovules was formed. The effect of different forms and concentrations of nitrogen on ovule formation and pistil growth was investigated. High concentrations of nitrate (40 mil) favored pistil growth and ovule formation, but comparable levels of ammonium were toxic. When ammonium at concentrations above 10 mM was added to nitrate media, ovule formation was inhibited. A medium containing low concentrations of ammonium (10 mM) and nitrate (5 mM) supported more ovule formation and pistil growth in young pistils than a low‐nitrate (5 mM) medium without ammonium. However, ovule formation on a medium containing 10 mM ammonium and 5 mM nitrate was significantly less than on a medium containing only 15 mM nitrate. Low concentrations of organic nitrogen in the form of α‐alanine (1 mM) and γ‐aminobutyric acid (5 mM) supported ovule formation and pistil growth similar to a high nitrate medium.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb05938.x

出版商:Wiley    

年代:1973

数据来源: WILEY