The relation of growth and swelling of plants and biocolloids to temperature

Abstract

The varying constitution and resultant water-relations of the plants may be simulated by mixtures consisting of agar and albumen, or albuminous derivatives, or most successfully by proteins extracted from beans or oats.

The swelling of living and dried sections of plants and of dried plates of such biocolloids in various solutions has been found by the author to depend upon the history or previous treatment of the material, the proportions of protein or albuminous derivatives, and pentosans present, concentration of the solutions and the temperature.

According to Taylor heat should diminish imbibition in gels, while cold and pressure will increase it. 1 The velocity and swelling capacity of two biocolloids at temperatures within the range of growth of plants used for comparison are illustrated by the following auxographic measurements expressed in percentages of increase of the original diameter of sections of dried plates:

The sections swelled at temperatures of 15-23° C., were 20 mm., those at higher temperatures, .18 mm. in thickness.

Plates of agar, 90 parts and oat-protein, 10 parts, show the highest hydration capacity of any mixture tested, the measurements obtained being as follows:

The swelling of discs 10-12 mm. in thickness, cut from joints of Opuntia, in water and salt solutions in illustrated by the following measurements:

The swelling of the biocolloids is seen to increase in initial velocity and total amount to a maximum between 39° and 46° C. in the salted mixture, and to 46° C. in the unsalted plates. The sections of plants increase similarly to a point undetermined and the swelling may be much greater in preparations freed from mechanical tissues. These increases are parallel to accelerations and retardations of growth by living plants under the influence of temperature.