Morphological and Biochemical Evidence for Cold-Stress-Induced Apoptosis in Meristematic Cells of Maize Roots

Previous study using in vitro system showed that cold stress could induce programmed cell death (Koukalova et al . 1997). In this study, the characteristic morphological and biochemical features of apoptosis induced under cold stress in meristematic cells of maize roots were detected at chromosomal, nuclear and DNA levels simultaneously and the DNA breakage was quantified using DNA laddering and chromosome spreading based TUNEL techniques (Figs.3～6). The statistical result on root growth showed that cold stress could suppress the growth of maize roots (Fig.1) and this suppression could be released under normal temperature (Fig.2). Non random degradation of nuclear DNA (shown as DNA Ladder in electrophoresis pattern) (Fig.3) and characteristic morphological changes (Figs.4,5) and the sequence of the changes of chromosome and nucleus suggested that apoptosis pathway be activated in maize roots in vivo . These results provided valuable insight into the physiological mechanism of cold resistance in plants.