Plant oxygen consumption

Vincamine (91) is the major alkaloid of V. minor, a plant used against headache and vertigo. It exerts a sedative CNS action and produces a fall in blood pressure. The principal activity is a moderate cerebral vasodilation. Clinical studies have demonstrated that i.v. administration of 91 to humans reduces the arterial blood pressure and increases cerebral blood flow and oxygen consumption. The improved cerebral hemodynamic conditions significantly and positively affect the state of patients with advanced arteriosclerosis with beneficial effects on memory, concentration, and behavior. It has thereafter been introduced under several trade names as a pharmaceutical in many European countries (232). Vobasine (32) has been widely studied it exhibits a weak CNS depressive, analgesic, and antipyretic action (21). 

A colleague who has to survey the water quality in River A tells you that he needs to quantify the oxygen consumption in the river downstream of a sewage discharge. He shows you the following measurements of dissolved oxygen as well as concentration data for tetrachloroethene (PCE) that is introduced into the river with a constant input by the sewage plant. 

Ethylene and carbon dioxide are produced by the plant cells in the culture and their respective headspace concentrations increase in the stoppered flasks. As expected, oxygen consumption by the cells results in reduction of the head-space composition. Specific 02 consumption rate and biomass accumulation curves as a function of time are presented in Fig. 2. The biomass accumulated at a rate of approximately 0.05 gdw 1 1 h the average specific 02 consumption rate calculated as 0.05 mmol gih v h The same data plotted as specific 02 con-... 

A reaction associated with nonphosphorylating oxygenases is shown in Reaction 4, an example of a minor oxygen-consuming reaction in biological systems. The oxygen consumption by cytochrome P-450 occurs in the microsomes of animals and the microbodies of plants. 

Four types of oxygen consumption occur in plants dark respiration, photorespiration, chloroplast respiration, and cyanide-resistant respiration. Other reviews of photorespiration have been published 41, 42) therefore it will not be discussed here. Also, because knowledge of respiratory ETS in plants is based on the higher plants in contrast to the algae, this section will be confined largely to the higher plant literature. 

FIGURE 4.3 Variation of dissolved oxygen content of pond water with aquatic plants as affected by photosynthetic activity accompanying sunshine, and metabolic oxygen consumption during dark hours. Data plotted from Klein [13]. 

The configuration of a 7000 MTPD DME plant is based on the combination of methanol synthesis and methanol dehydration. Attractive features of this process include lesser total investment cost and lesser oxygen consumption when compared with the methanol/DME coproduction route or direct DME synthesis route. Also, carbon dioxide is not produced in the DME synthesis step of this process. As shown in Fig. 6, this process utilizes a steam reformer, TEC s TAF-X reactor, oxygen reformer, TEC s MRF-Z methanol reactor, and TEC s DME reactor. 

Nitralin inhibits the root growth of sensitive plants by disrupting primary cell wall formation during cell division (Centner and Burk, 1968). Like trifluralin, it inhibits oxygen consumption and oxidative phosphorylation in vitro in the isolated mitochondria of maize, millet and soybean (Negi et al., 1968). 

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