Handbook of Plant and Crop Physiology

D. Manganese

Methylcyclopentadienyl manganese tricarbonyl (MMT) is currently added to gasoline to replace
tetraethyl lead as an antiknock fuel additive. Manganese concentrations in roadside soil and plants are in-
creasing and correlated with distance from the roadway, traffic volume, plant type, and microhabitat.
Radish (Raphanus sativusL.) seedlings were treated for 5 to 35 days with different levels of manganous
chloride (0–1000 ppm). Metabolic heat rates and respiration rates, measured calorimetrically, indicated
severe stress at Mn concentrations between 10 and 100 ppm and at temperatures above 20°C [39].

VIII. CONCLUSIONS

Plants acclimate or adapt to survive and grow in the presence of environmental stresses. The degree of
adaptation to a particular stress can be monitored by measuring the rates of metabolic heat loss (q) and
catabolism of photosynthate (RCO2). Because growth and defense against environmental stresses rely on
energy release from metabolic substrates, subtle degrees of adaptation can be determined using
calorimetry. It is now possible to select rapidly populations or cultivars for growth in a particular mi-
croenvironment. The result may be increased food production and more effective environmental
conservation.

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