Salt Concentration and Reversibility of Ice-Formation as Related to the Hardiness of Winter Wheat

Abstract

Although the conditions of ice-formation in the tissues of plants have been the subject of numerous investigations, in the literature there appears to be no description of detailed quantitative experiments regarding the reversibility of the process of ice-formation. In several papers the reversibility or irreversibility of the process is implied. Thus, showed that the freezing point of tissue was lower on the first freeze than on refreezing, which suggests irreversibility; NEWTON and GORTNER (15) specifically warned against refreezing the sample of expressed sap in determining "bound water." To the contrary, irreversibility might be implied by the technique used by STEINMETZ (20), who froze samples of alfalfa roots at an extremely low temperature, before expressing the sap to be used in "bound water" studies.The question of reversibility of ice-formation in non-living colloidal systems has been repeatedly investigated. (Cf. JONES and GORTNER (11) for recent literature.) Such systems are sometimes indicated as "elastic gels" when reversible, and "non-elastic" gels when irreversible.That the capacity for reversibility might well be significant in a consideration of winter-hardiness is brought out by casual observation of frozen plants as they thaw out. One may observe that, hardy and tender alike, the plants immediately after thawing have a water-soaked appearance; in the case of hardy plants, however, this water is reabsorbed in the course of a relatively short time and the plants regain their former appearance. If a temperature too cold for the survival of the hardy plants is used, this reabsorption does not occur.WAhen plant tissues freeze, the formation of ice removes water from the sap, thereby concentrating the solutes in the unfrozen water until the cryohydric point is reached. A study of the concentration of the minerals under such conditions is of interest, since "salting out" of colloids, often irreversibly, is a matter of common occurrence.Experimental material To examine this problem in an experimental way the following procedure was followed. Field plats of four varieties of winter wheat were seeded

Growth and Development of Hardy and Nonhardy Wheat Varieties (Triticum aestivum L.) at Near‐freezing Temperatures1

“…The major fluctuations in percent dry matter were common to both varieties within each planting and occurred during the same time intervals. This may indicate the physiological hardening of both varieties in response to environmental conditions (6).…”

“…The number of roots growing from the crown region, the number of leaves, and the number of tillers developed were considered as direct evidence for growth at the crown level. Approximate leaf blade area (I) and percent dry matter were correlated with the other data with reference to over-all metabolic activity (6,10).…”

“…Suneson and Peltier (12) noted that wheat seedlings still dependent upon seed endosperm were more cold tolerant than similar seedlings that were nearing endosperm independence. Dexter (6) reported that hardiness was generally associated with a high percentage of dry matter.…”

Research on Quick Freezing Technology of Sword Bean (<i>Canavalia gladiate</i>)

“…[6,7] and chemical changes (protein denaturation, losses of vitamins and amino acids and magnesium removal of chlorophyll etc. [8,9,10] occur during freezing of vegetables, and reversibility of these changes is of great importance for quality maintaining of frozen products [11]. Reversibility of freezing process depends on the number and size of ice crystals formed during freezing.…”