摘要:

Various growth characteristics were measured throughout ontogeny for barley plants (Hordeum vulgareL. cv. Brant) grown in silica sand and irrigated daily with one-eighth (0.125N), one-fourth (0.25N), and one-half (0.5N) dilutions of a modified Hoagland nutrient solution, at day–night temperatures of 25–20 °C, an irradiance of 53 nE cm−2 s−1(400–700 nm), and a day length of 15.5 h.The net CO2exchange rate (NCE) of newly matured leaf laminae did not differ between measurements made at the same irradiance before and after noon. By contrast, NCE was greater at all stages except stem elongation for plants supplied with 0.5Nnutrient solution than for those receiving 0.25Nand 0.125Nsolutions. The nutrient effect was apparent even for the first leaf produced. A distinct ontogenetic pattern of change in leaf NCE was apparent under all nutrient treatments: NCE increased from leaf 1 to leaf 3, remained constant between leaf 3 and leaf 5, declined between leaf 6 and leaf 9, and then increased markedly from leaf 10 onwards. The changes in leaf NCE appeared to be associated with major events in ontogeny.Rate of leaf appearance was constant through ontogeny and was not affected by nutrient supply. Final leaf number was greater for the 0.5Nnutrient solution. Leaf length, width, area, and specific weight increased throughout the early stages of ontogeny, and decreased later. The decrease in leaf length and area was less for plants supplied with more nutrients.

ISSN:0008-4026    

DOI:10.1139/b75-264

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Plastids were isolated from 4- to 8-day-old seedlings of Gateway barley and its virescens mutant. At 4 days the normal barley plastids were well developed with respect to chlorophyll content, ultrastructure, and photoreductive activity. In contrast the mutant plastids were low in chlorophyll, contained predominantly single thylakoids, and their activity was low at this stage. By 8 days the amount of chlorophyll in the mutant plastids had increased, they had well-developed grana and their photoreductive activity reached normal levels. There seemed to be a correlation between the structure of photosynthetic membranes and their photoreductive activity during the development of the mutant barley plastids. It was concluded that chlorophyll content did not limit photoreductive activity at the earliest stage of development.

ISSN:0008-4026    

DOI:10.1139/b75-265

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The 10- to 12-h lag phase in chlorophyll accumulation preceding the rapid accumulation phase inLemna minorde-etiolating in the light was eliminated by a red light preillumination given about the length of the lag period before the onset of continuous red light. Neither the rate after the lag nor the extent of cholorophyll accumulation differed between preilluminated and control plants. Both the rate of accumulation in controls and the absolute stimulation by preillumination were shown to depend upon the length of time the etiolated plants had been grown in darkness up to 93 days. Only one photoproduct of preillumination contributed to the elimination of the chlorophyll lag phase, but the effect of red light was only partially (about 60%) nullified by subsequent far-red light.

ISSN:0008-4026    

DOI:10.1139/b75-266

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Electrophoregrams of soluble proteins of winter wheats (Triticum aestivumL.) after incorporation ofL-[14C] leucine disclose the synthesis of two particular proteins during the cold hardening processes of the hardier variety, Kharkov, compared with a less-hardy variety, Selkirk. The composition in amino acids of the two proteins has been studied and shown to confer them a higher degree of hydrophily making them capable to bind and retain vital water with enough energy to avoid too much dehydration resulting in denaturation during extracellular ice formation.

ISSN:0008-4026    

DOI:10.1139/b75-267

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Investigations of quantitative and qualitative changes in protein synthesis in two winter wheat varieties have been made during the early stages of cold hardening. When labelling with35S is made during the hardening treatment, the incorporation of the tracer into proteins is very low in both varieties. However, if labelling at 22 °C precedes hardening, the hardy variety, Kharkov, shows an increase in the incorporation of35S into the total soluble proteins, and the rate of synthesis of both chloroplast and membrane proteins is maintained during the hardening process. In the less-hardy Selkirk, a very marked decrease in proteogenesis has been observed.Qualitative studies on the incorporation of35S have not revealed any changes in specific chloroplast and membrane proteins during early stages of cold hardening of the two varieties of winter wheat.

ISSN:0008-4026    

DOI:10.1139/b75-268

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Tobacco stunt virus (TSV) was mechanically transmitted to 41 species in 9 families: i.e., Aizoaceae, Amaranthaceae, Apocynaceae, Caryophyllaceae, Chenopodiaceae, Cucurbitaceae, Leguminosae, Pedaliaceae, and Solanaceae. TSV remained infective for 60 h in 0.001 M1-phenylthiosemicarbazide (1-PTC) in 0.01 Mphosphate buffer, pH 6.8, but was infective only immediately after extraction in phosphate buffer. TSV in 1-PTC-phosphate buffer had a thermal inactivation point between 75 and 80 °C and a dilution end point between 10−2and 10−3. Comparative studies made on reaction of host plants, serological reaction, and cross protection indicate that TSV is unrelated to a California isolate of tobacco necrosis virus.

ISSN:0008-4026    

DOI:10.1139/b75-269

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Tracyella(Sacc.) Tassi, type speciesT.spartinae(Peck) Tassi, is redescribed.Tracyella aristata(Cooke) Tassi is accepted as the second species of the genus,T.andrasovszkyiMoesz is considered as anomen dubium, andT.julia(Speg.) Moesz andT.minima(B. & C.) Moesz are excluded. It is suggested that a fungus recently reported from graminaceous hosts under the nameAmerodiscosiella renisporaFarr is in factT.spartinae.AmerodiscosiellaFarr andA.renisporaare maintained as distinct, if doubtful, taxa of unknown affinities.

ISSN:0008-4026    

DOI:10.1139/b75-270

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Impermeability to OSO4of periderm-free zones around the feeding sites of balsam woolly aphid (BWA),Adelges piceae, in the bark ofAbies, was caused by a non-suberized impervious tissue (NIT). NIT developed at mechanical injuries in living bark ofAbies grandis,Abies amabilis,Tsuga heterophylla, andThuja plicatain 3 to 4 weeks during summer. It was found at healed injuries regardless of the cause, biotic or abiotic, at abscission scars, and at old resin blisters and rhytidome. It is concluded that NIT precedes formation of necrophylactic periderms (NP), may provide environment necessary for NP formation in tissues internally abutting NIT, and is a marker for distinguishing NP from exophylactic periderms. The imperviousness of NIT to water resulted neither from suberin (seven tests) nor from callose (three tests), and was detected by an F–F test, which is based on penetration of 2% FeCl3followed by 4% K3Fe(CN)6through the bark for 3 days each. The formation of NIT in the absence, e.g. rhytidome, as well as in the presence of injuries, BWA, and disease agents, suggests that NIT production is not only a non-specific inherent process but may be the physiological basis of host response to diseases in bark. Pathogen-free, "non-induced" NIT formation at rhytidome as a control process for isolating the host component of host–pathogen interactions is discussed.

ISSN:0008-4026    

DOI:10.1139/b75-271

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

A plant pathogen,Microsphaeropsis centaureaeMorgan-Jones, was found to be parasitic on the sclerotia ofSclerotinia sclerotiorum(Lib.) deBary.

ISSN:0008-4026    

DOI:10.1139/b75-272

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The type genus of the family Seuratiaceae is described as consisting of four highly variable species. The origin and location of the conidiogenous areas (sporodochia), pycnidia, and pseudothecia are demonstrated to be related to the size and shape of the colonies, which are in turn dependent upon ecological factors of substratum and duration of wet season. The microstructure of the intercellular matrix varies from amyloid through pseudoamyloid to inamyloid. Each of these characteristics completely intergrades between the extremes. The pattern is considered to reflect nutritional differences rather than climatic factors. Asexual reproduction is by multicellular, holoblastic thallospores originating from superficial layers of the colonies. The variation of the thallospores (conidia) arises from indeterminate but ecologically limited growth. Asci arise from superficial croziers which proliferate indefinitely before aborting. The zone of ascogenous tissue is therefore a pseudothecium. Pseudoparaphyses are lacking but an indefinite epithecium is sometimes found. Interthecial tissue arises from budding croziers or by their abortion and from persistent sterile tissue. With the production of mature asci, colonies cease to grow and soon drop from the leaves.

ISSN:0008-4026    

DOI:10.1139/b75-273

出版商:NRC Research Press    

年代:1975

数据来源: NRC