Under the salinity condition, coefficients of variation of a majority of parameters were larger than those under the normal condition (Table 1). Cu plasm type showed significantly lower total path and cytochrome path activities than CS, and C and Sv plasm types showed lower total path activities. It was noted that the alternative path activities of six plasm types were higher than CS under the salinity condition. The alternative path is known to be operative uniquely in plants under the conditions of energy oversupply or limited cytochrome path capacity (Moore and Siedow 1991). The path is resistant to cyanide and the electron flow through this path is considered to be energetically wasteful because of the uncoupling with ATP production. Although physiological significance of this path remains unclear, it has been suggested that the path plays a role in maintaining the homeostasis of plant cells in relation to cellular energy states (Lambers 1982). The observed higher alternative path activity in one half of the alloplasmic hybrids than CS under the salinity condition suggests that the energy overflow through this path is associated with the limited capacity of the cytochrome path in these alloplasmic hybrids. The response of plasm types to NaCl salinity, i.e., increases or decreases in the respiratory path activities relative to those under the normal condition, is shown in Fig. 1. NaCl salinity caused significant increases in the total and cytochrome path activities in CS. The observation is consistent with the report that the cytochrome path activity increases in wheat plants subjected to NaCl salinity, possibly to cope with the increased energy demand under salinity conditions (Zagdanska 1995). similarly, Sl, Mt, Mt2 and Sv plasm types showed increases in both total and cytochrome path activities under the salinity condition. On the other hand, the salinity condition caused significant decreases in the total path activity and/or cytochrome path activity in D, Mh and G plasm types.

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