摘要:

The hypocotyls of red clover seedlings, when sprouted on a seed bed enriched with crude Bios 2, grew upwards in a vertical position, while the cotyledons rested on the surface, supporting the inverted plant and possibly absorbing nutrients for its growth. From the tip of the upturned primary root, secondary roots developed about ten days after seeding. These new roots grew downwards, and after approximately one week, they penetrated the substratum in a normal fashion.The concentration of crude Bios 2 necessary to cause maximum hypocotyl bending, was observed to be approximately four times that required to produce optimum stimulation of the nodule bacteria.When plants were allowed to start in an unenriched growing medium superimposed on a layer of agar enriched with crude Bios 2, no upward bending of the roots occurred as they reached the Bios layer.Bios 2(b) alone appears to be the factor responsible for the hypocotyl bending phenomenon. Bios 1, Bios 2(a), pantothenic acid, various amino acids, and miscellaneous compounds were tested and did not appear active in this respect.Though causing a different form of root aversion, hetero-auxin, like Bios 2(b), actually prevents the hypocotyls from entering an enriched medium. While the two substances bring about a certain similarity of physiological effect, they cannot be considered identical, and chemically, they are absolutely distinct.A drop of Bios 2(b) placed on the sensitive parenchymous lining of a bean pod caused rapid cell multiplication, resulting in the production of a wart-like protuberance. Similar, though somewhat less distinct results followed the pricking of such tissue with a pin. These results would appear to strengthen the hypothesis advanced by Went in which Bios was assigned the properties of a "wound hormone".

ISSN:1923-4287    

DOI:10.1139/cjr37c-001

出版商:NRC Research Press    

年代:1937

数据来源: NRC

摘要:

An investigation of the response of the vascular cambium to wounding in leader shoots of the balsam poplar,Populus balsamiferaL., was carried out in the laboratory during the winter months, at which time observations on local wound cambial activity, distinct and apart from normal cambial activity, can be obtained. It was found, in disbudded units, that the greater the amount of living bark distal to a wound, the greater is the development of local cambial activity in relation to the wound. Local wound cambial activity is further promoted by the presence of developing buds and leaves distal to the wound, and the effect can be observed before the basipetal gradient of normal cambial activity emanating from the developing extension growth has reached the wound. Cambial activity in relation to wounding responds to gravity in the same way as normal cambial activity. In horizontally placed leader shoots, cambial activity is greater in relation to a wound on the upper side of the shoot than to a similar wound directly opposite on the lower side. On the basis of these results, it is suggested that a hormone, present in the living bark and also produced by developing buds and leaves, is involved in local wound cambial activity. In all probability this hormone is identical with that which promotes normal cambial activity.It is also suggested that a wound substance, capable of promoting by itself cell division only, is involved in local wound cambial activity. The amount of this wound substance produced is apparently proportional to the extent of dying of the cells of the bark subsequent to wounding. From the lower edge of a complete ring, a very feeble basipetal gradient of cambial activity arises, in which differentiation to form vessels and fibres does not occur, although a few tracheids may be found. This type of behavior has not hitherto been reported, and is interpreted as the result of stimulation of the cambial layers by the wound substance alone. Local cambial activity above a complete ring and in relation to bridged wounds, involves differentiation of more or less typical vessels and fibres, and is interpreted as the result of interaction between the wound substance and the cambial hormone traveling basipetally in the living cells of the bark. The absence or feebler development of cambial activity at certain points in relation to bridged wounds, in contrast to greater development at other points where presumably the concentration of cambial hormone must be less, is interpreted as the result of lack of wound substance or low concentration of it acting as a limiting factor.

ISSN:1923-4287    

DOI:10.1139/cjr37c-002

出版商:NRC Research Press    

年代:1937

数据来源: NRC