Cold Tolerance in in Vitro-Grown Seedlings, Callus Tissue, and Somaclones of Maize

Abstract

Using cold test methods, the germination, emergence, and percentage emergence were studied in cold soil or at room temperature following cold treatment (Kovács 1961; Pesev 1970; Herczegh 1978; Eagles and Hardacre 1979; Szundy and Kovács 1981a,b; Eagles 1982; Stamp 1984; Nagy et al. 1984). The soil usually originated from a field of maize monoculture so that the conditions in the experiment could be close to those in the field. This means that the seeds and embryonic plants were affected simultaneously by cold and by the pathogenic microorganisms of the soil. This explains why the differences between Hybrids were less than within Hybrids (Rush and Neal 1951). In an experiment of this type, one cannot decide the effect of cold only. Dickson (1923) reported that maize seeds and seedlings were destroyed by Gibberella saubinetii (Mont.) Sacc. at 8 °C, but seeds emerged without damage at 24 °C. This condition after treatment at 8 °C resulted in low physiological activity in seeds and embryos; they were also attacked by fungi for a long time. The development of maize seeds after cold treatment was determined by the interaction between pathogen fungi and temperature and not by the maize genotypes. The effects of cold treatment on maize leaves were studied by Baker et al. (1983) and Long et al. (1983). The degree of damage was greater at a lower temperature and after a longer period of cold treatment. After cold treatment, leaves photosynthesized at 20 °C less effectively than the control at 20 °C. Creencia and Bramlage (1971) noted that the growth of cold-treated plant leaves is slower at 21 °C than in the control. The primary roots of maize grown in nutrient solution at 5 °C elongate at about 1% of the rate found at 20 °C but cell proliferation is still possible at 5 °C, and the maximum elongation rate achieved by roots during the recovery period was less than that of roots which had not experienced cooling (Barlow and Adam 1989). Leaves and roots in general show damage after a cold period, but not enough data are available in the literature on embryonic plants.