摘要:

Complete analyses of pollen-mother-cell nuclei at first metaphase, percentage good pollen, pollen diameter and pollen-size distribution were determired for the following poplar species and natural hybrids:Populus grandidentataMichx.,P.tremuloidesMichx.,P.eugeneiSimon Louis,P.albaL.,P.canescensSm., natural hybrids ofP.alba×P.grandidentataand ofP.alba×P.tremuloides.Both of theP.albaand two of the fourP.canescenstrees examined were triploids (2n = 57) while all other trees examined were diploids (2n = 38). Meiotic observations on the natural hybrids indicated a high degree of homology between the chromosomes ofP.albaand the native aspens (P.grandidentataandP.tremuloides), since 17 to 19 bivalents were usually found at first metaphase. In collections from one triploidP.canescensand two diploidalba-grandidentatahybrid trees, failure of a high proportion of the chromosomes to pair was attributed to genetic factors limiting pairing, rather than to non-homology.Pollen characters such as percentage good pollen, pollen diameter, and pollen size distribution were, in most cases, not indicative of the chromosome number or pairing relations at first metaphase. Consequently, triploids could not be detected by pollen observations under the conditions of this experiment. In spite of the lack of correlation between first metaphase and pollen observations, abnormally large pollen grains were observed in collections from several of the trees, and these were considered to contain the diploid or unreduced chromosome complement. The tendency for the poplars to produce unreduced pollen grains probably accounts for the number of triploid trees discovered in Canada and Sweden.

ISSN:1923-4287    

DOI:10.1139/cjr38c-041

出版商:NRC Research Press    

年代:1938

数据来源: NRC

摘要:

Investigations made with samples representing 12 varieties of barley, grown at 12 experimental stations in Canada, show that fairly close intra-varietal correlations exist between the total nitrogen of barley and the saccharifying activities of the barley and of the malt made from it; and that these correlations are closer than the corresponding correlations with nitrogen fractions. No inter-varietal correlation exists between saccharifying activities on the one hand, and total nitrogen, alcohol-soluble nitrogen, or insoluble nitrogen, on the other, but inter-varietal correlations appear to exist between saccharifying activities and the more soluble nitrogen fractions.The correlations between the nitrogen, or nitrogen fractions, and total barley saccharifying activity (papain method), and between the nitrogen, or nitrogen fractions, and free malt saccharifying activity (Lintner value), are closer than the corresponding correlations for free and latent barley saccharifying activities. Latent barley saccharifying activity is more closely correlated with total nitrogen than with any of the nitrogen fractions studied.A study of the multiple correlations between malt saccharifying activity, and total nitrogen and 1000-kernel weight of barley, shows that the improvement resulting from the introduction of 1000-kernel weight as a second independent variable is very small.

ISSN:1923-4287    

DOI:10.1139/cjr38c-042

出版商:NRC Research Press    

年代:1938

数据来源: NRC

摘要:

Observations in a micro-freezing apparatus of isolated tissues of the cortex of hardy and non-hardy plants ofCatalpaandCornusspecies, and of the epidermis of red cabbage, reveal that there are two modes of freezing of plant cells, intracellular and extracellular.In intracellular freezing, ice crystals form first in the protoplasm and then in the vacuole. In extracellular freezing, ice forms outside the cells from water in the cells. The resulting dehydration of the cell causes its collapse, the opposite walls coming together and squeezing the contents to the periphery. Intracellular freezing is fatal to all cells by visible mechanical disruption of the protoplasm and vacuole. It is facilitated by rapid freezing and occurs less easily and less frequently in hardy tissues and in trees and shrubs than in non-hardy and herbaceous tissues. Extracellular freezing induced through slow cooling is fatal to all unhardy cells in trees and herbs at all temperatures below the freezing point, and to cells of hardy cabbage only at − 10 °C. to − 15 °C., but not to cells of hardy trees and shrubs.Both types of ice formation have been observed in intact plants of red cabbage frozen in a refrigerator.The behavior of hardened plants shows that intracellular freezing tends to be prevented in them by an increased permeability to water. In regard to extracellular freezing, from the behavior of the cells on freezing and in micrurgy, a mechanical injury hypothesis is presented.

ISSN:1923-4287    

DOI:10.1139/cjr38c-043

出版商:NRC Research Press    

年代:1938

数据来源: NRC