| Abstract: | Respiration in isolated mung bean shoot mitochondria was notaffected by either of the tomatine treatments (10–3 M,pH 5, and 10–5 M, pH 8) but was reduced in the excisedshoots by both treatments, although only at the higher of thetwo temperatures (5 °C and 25 °C). Inhibition was gradualand took at least 2 h. Tomatine treatment of excised shootsalso resulted in an increased leakage of K+. PS II activityin isolated spinach leaf chloroplasts was reduced only by thehigh pH tomatine treatment at 25 °C. Again, about 2 h treatmentwas required before significant effects were observed but thealkaloid did not cause disintegration of the chloroplast asmeasured by pigment release. Disruption of lysosomes isolatedfrom cauliflower inflorescence tissue and release of acid phosphatasewas enhanced by tomatine. Initially only 10–5 M tomatineat pH 8 was effective but, later, effects could only be obtainedwith 10–3 M alkaloid at pH 5. The differential susceptibilityof these organelles to tomatine is discussed in relation tomembrane structure and to the mode of toxicity of the alkaloid. |
