1968 Volume 1968 Issue 29 Pages 1-5
To determine the frost hardiness of the tea plant, evaluations of the frost injury by measuring the electric conductivity of exosmosis of frozen leaves were investigated.
Approximately 3g. of frozen leaves is infused in 150 ml. distilled water at 20°C for 20 hours, after which period the electric conductivity (μÖ/cm2) of the liquid is measured (denote by A), and unfrozen control sample is also measured (B). To determine the amount of electrolytes diffused from the completely killed leaves, sample is infused in boiling water and the electric conductivity of the liquid is measured (C).
With regard to the above values, the following model equations are postulated
A=α(1-β)e+βe
B=βe
C=e
where α is the percentage of the frost injury, showing a reasonable approximation of the percent of tissue destroyed by the freezing treatment, and Q is the percentage of diffused electrolytes of uninjured leaves, and e is the amount of electrolytes which diffused from the completely killed leaves.
Thus the degree of frost injury can be estimated by the equation :
α=A-B/C-B×100
Various clones were tested for frost hardiness in midwinter using this method, consequently it was presented that the value of α was nearly corresponded with the visual observations on the frost injury. The above correspondence, however, was not so consistent, because the visual observations might be fluctuated in cases of too severe or too slight demage to leaves by the artificial freezing treatment, and in cases of using the injured or discoloured samples. The value of (A-B) should be useful for a substitute value of the degree of frost injury.
