摘要:

I propose a set of 11 soybean varieties for the differentiation of races ofPeronospora manshurica:Pridesoy, Norchief, Mukden, Richland, Roanoke, Illini, S 100, Palmetto, Dorman, Kabott, and Ogden. When I employed these, I found fifteen new races ofPeronospora manshurica, the casual agent of downy mildew of soybeans, described them, and assigned numbers 9 through 23. Race 8 was encountered most frequently and occurred at 40% of the locations from which seed samples were obtained. Races 1, 2, 10, 12, 18, and 23 occurred at 5–8% of the locations sampled. Race 10 was common in the southern U. S. Of 247 soybean seed lots sampled, 73% contained some oospore‐encrusted seeds. These ranged from 12–26% lighter than healthy seeds. The percentage of oospore‐encrusted seeds occurring in seed lots ranged from 0–25%.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09964.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Periodic cell divisions were induced in gametophytes ofPteridium aquilinumby daily irradiation with white light. In white‐dark cycles, the rate of cell division was promoted by increased time in white light; cell elongation was not affected. The time of transition to two‐dimensional growth (days to 5% 2‐D) was closely associated with the mitotic rate. For white‐red cycles, the rate of elongation was controlled by the intensity of red light (wavelengths over 550 nm). This increased elongation delayed the initiation of 2‐D development. In both cases the rate of transition to 2‐D growth was correlated with the amount of elongation per division.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09965.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Eight species ofCordylanthus(Scrophulariaeeae: tribe Euphrasieae) representing the three major sections of the genus were successfully grown both with and without a host plant, demonstrating that the plants are facultative hemi‐parasites capable of completing their life cycle without a host under the favorable conditions of greenhouse culture. The plants are almost certainly parasitic in the wild. Even though haustorial connections were formed byCordylanthuson the roots of all host plants provided, most species were more vigorous when growing with certain hosts(Quercus, Pinus, Helianthus)than with others(Plantago, Phleum). This indicates a difference in the ability of the parasite to obtain materials successfully from the various plants used as hosts. Natural hosts are inferred for 15 species ofCordylanthusfrom the presence of associated species in nature. The haustoria are exogenous in origin, being formed by dedifferentiation of several cells in the hypo‐dermal or subhypodermal layers of the rootlets. Anatomically the haustoria differ from those reported for other members of Euphrasieae in having secondary vascular structure and abundant connecting strands. The vascular structure of haustoria is composed mainly of specialized vessel elements. Root‐parasitism givesCordylanthusthe ability to grow in arid areas during the summer after most other annuals have died, thus successfully equipping the plants for survival and expansion in western North America.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09966.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Certain aspects of protocorm development inVandawere examined ultrastructurally. The parenchymal cells of the protocorm accumulate substantial quantities of lipid, protein, and carbohydrate reserves which disappear gradually with the senescence of the parenchymatous region. The proteinaceous reserves appear initially as discrete bodies which become intimately associated with clusters of small tubules. The tubules eventually disperse throughout the cytoplasm and disappear following depletion of the protein bodies. The lipid reserves also appear as discrete bodies and are associated with an electron dense, laminated inclusion which appears to increase in size with the disappearance of the lipid bodies. While plastids in the meristematic cells differentiate a well‐developed thylakoid system and contain little starch, those of the parenchymal cells contain large starch grains and numerous osmiophilic droplets and develop meager thylakoid systems. Membrane‐bound crystalline structures of hexagonal and rhomboid cross section occur frequently in the cytoplasm of senescent parenchyma cells. Trichome initials, which differentiate from the epidermis, contain few conventional organelles and exhibit numerous membrane‐bound structures containing many small crystalline inclusions. Numerous vesicles accumulate at the tips of the trichomes in spaces between the cell wall and the plasmalemma.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09967.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Lyssoxylon grigsbyiDaugherty, a petrified stem with petiole bases, was originally described from the Upper Triassic Chinle Formation of Arizona and considered to be a member of the Williamsoniaceae. Investigation of additional material from a similar horizon in New Mexico, together with re‐examination of preparations of the holotype, suggest that the plant, with its monoxylic stele, girdling leaf traces, and bicelled epidermal hairs is a true cycad. Cells of the New Mexico specimens contain structures interpreted as preserved nuclei.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09968.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Methyl decanoate emulsified with Tween 20 and sprayed on chrysanthemum plants kills the immature tissues. The mechanism of selectivity was found to be a property of the cuticle which acts as a penetration barrier to the emulsion. Disruption of cuticles before emulsion application resulted in death of underlying cells due to membrane destruction, as shown by electron microscopy. Small quantities of methyl decanoate, however, do penetrate the unaltered cuticle, resulting in moderate, reversible alterations to the ultrastructure of the cell. These alterations appear as aggregates of vesicles in the cytoplasm and larger aggregates of vesicles in the vacuole. No destruction of organelle membranes occurred, and visual symptoms were not seen. The marginal cuticular penetration was verified by isolated cuticle tests.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09969.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Sixteenn‐alkanes were isolated and identified from the herbClarkia unguiculata, fourteen fromC. exilisand seven fromC. tembloriensis. These alkanes ranged from C20H42to C35H72. In all three taxa, the odd numbered alkanes were generally present in greater quantities than even numbered ones, which is similar to the alkane patterns ofMonardathat were observed in our laboratories.Clarkia tembloriensishas a characteristically high percentage (95%) of the C20alkane.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09970.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Two populations derived respectively from callus tissue of sugarcane clones H 37–1933 and H 50–7209 were studied for differences in morphology, chromosome number, and four enzyme systems. Variations observed in morphological characteristics were not directly correlated with differences in enzyme systems. Greater variation in both respects was observed in plants from the H 50–7209 (a chromosomal mosaic) population than in plants from the H 37–1933 (chromosomally stable) population. Among 37 plants of H 50–7209, all but one had cell‐to‐cell variation in chromosome number. In all but one of these 36 variable plants, the overall range was 2n = 94–120. The exceptional plant had a range of 2n = 17–118. Among 8 plants of H 37–1933, all had 2n = ca. 106.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09971.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

An intensive study has been made of the general structure and varied topography of blind vein‐endings in the dichotomous venation ofCircaeaster agrestisMaxim. The venation patterns of leaves of plants collected in various parts of the geographical range of this species as well as the vasculature of leaves of specimens raised in a growth‐chamber have been studied and compared. Blind endings may be associated in various ways with the branches of simple terminal vein‐dichotomies and are either intrusive or extrusive in position. Descriptions are also given of the various relations between intrusive and extrusive blind endings and the more complex asymmetrical or symmetrical dichotomized vein‐systems found in various parts of the lamina. “Unlike the main veins of the leaf, which consistently vascularize corresponding marginal teeth, a blind vein‐ending usually extends toward or terminates directly below the sinus between two adjacent marginal teeth. There appears to be no correlation between the occasional formation of rudimentary marginal teeth and the development of blind vein‐endings. It is concluded that a well‐developed unbranched blind ending morphologically represents one of the vascular strands derived from a normal vein‐dichotomy. The smaller blind endings, associated with terminal vein‐dichotomies, are more difficult to interpret and possibly may represent “supernumerary” veinlets. The parallelism in topography between the blind endings in the leaves ofKingdoniaandCircaeasteris briefly discussed, and attention is also drawn to the occurrence of similar blind endings in the dichotomous venation patterns of perianth‐segments and petals of certain angiosperms.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09972.x

出版商:Wiley    

年代:1971

数据来源: WILEY