摘要:

Seed production inMedicago(alfalfa) hybrids is related to many factors, primarily the cytological disturbances due to hybridization. The establishment of new balances results in strains which may occupy different habitats. Deficiencies may appear at one or more of the many stages during the complete process of growth and development. This account on the normal ovule, as a standard for comparison, deals particularly with the histogenesis and development of the nucellus, gynospores, integuments, funiculus, female gametophyte, embryo and endosperm. Some of the food and nutrition problems associated with seed production are considered. A series of papers dealing with special phases of seed development in hybridMedicagois in progress.

ISSN:1923-4287    

DOI:10.1139/cjr41c-042

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

Eighteen stem rust resistant wheat varieties were tested, in the greenhouse, for their reaction to three physiologic races ofPuccinia graminis TriticiErikss. and Henn. at three different temperatures: a constant low temperature of about 60° F., a constant high temperature of about 80° F., and an intermediate temperature which fluctuated daily from 50° to 55° F. at night to 70° to 85° F. at midday.At the low and at the intermediate temperature some of the varieties proved immune while others proved highly or moderately resistant. At the high temperature five varieties (Bokveld, Iumillo, Gaza, Red Egyptian, and N.A. 95 Egypt) were immune or highly resistant; six varieties (Marquillo × Waratah, Hope, Hochzucht, Minor, Bobin Gaza Robin, and Federation × Acme) were moderately resistant; and seven varieties (Kenya, Syria, McMurachy, Sweden, Rhodesian, Talberg, and Eureka) were moderately or completely susceptible.

ISSN:1923-4287    

DOI:10.1139/cjr41c-043

出版商:NRC Research Press    

年代:1941

数据来源: NRC

摘要:

In recent years a destructive disease has affected tomato plants in certain greenhouses in central Ontario. This disease is characterized by a damping-off of seedlings and a rot of stems, fruits, leaves, and roots. The causal organism has been identified asPhytophthora parasiticaDast. The effects of various nutrient media, of temperature, of atmospheric humidity, and of the acidity of the medium on the growth of the fungus in culture have been studied.An extensive investigation has been made of certain factors affecting the parasitic activity of this soil-borne pathogen. Disease is favoured by high atmospheric temperature and high relative humidity. Disease incidence also varies directly with the moisture content of the soil and is maximum at soil temperatures near 22 °C. The ability of the pathogen to establish itself in soils depends upon the type of soil, upon the other micro-organisms present, and upon the substrate available for saprophytic development. The rates of invasion of non-infested soils were determined and found to be retarded by the competitive factor and accelerated by the presence of living roots of tomato seedlings. The activity of the pathogen is suppressed by the addition of soybean residue to infested soil.The potential host range of this isolant ofP.parasiticahas been partially determined by means of artificial inoculations.Several methods for the control of the disease were tried, and their value is discussed.

ISSN:1923-4287    

DOI:10.1139/cjr41c-044

出版商:NRC Research Press    

年代:1941

数据来源: NRC