Changes in the proportions of two forms of invertase associated with the cold acclimation of wheat

The proportion of two of the forms of invertase in wheat leaves is different when the plants are grown under cold-hardening conditions compared with under nonhardening conditions. Twelve varieties of bread wheat (Triticum aestivum L. emend. Thell. ssp. vulgare) of diverse levels of cold hardiness showed a high rank-order correlation between their level of cold hardiness and the ratio of peak I to peak II invertase in the leaves grown for 7–8 weeks at 6–4 °C. Similar trends were evident among four of these varieties grown for 11–13 or 20–24 weeks at 3 °C. No such correlations were observed in plants grown at 21 °C, i.e., under conditions that induce little or no cold hardening. The single durum wheat (Triticum durum Desf.) tested behaved somewhat differently.When plants of a single variety were grown under different hardening conditions, the cold resistance of the plants and the ratio of peak I to peak II invertase in their leaves were not closely related. However, cold-hardened common winter wheat varieties had much higher ratios of peak I to peak II invertase in their leaves than did similar varieties in the unhardy condition or cold-sensitive varieties.In the bread wheats, the amount of peak I invertase increases in plants grown under conditions causing cold hardening relative to that in plants grown at 21 °C while the amount of peak II invertase decreases. This suggests that one form of invertase replaces another during cold hardening.