Root herbivory

LAW 12] Lawrence S.D., Nov.ak N.G., Kayal W.E. et al., Root herbivory molecular analysis of the maize transcriptome upon infestation by southern com rootworm, Diabrotica undecimpunctata howardC, Physiologia Plantarum, vol. 144, pp. 303-319, 2012. 

Herbivory in benthic marine systems is intense. For example, on coral reefs, herbivores can remove almost 100% of the biomass produced daily by marine macroalgae, whereas in the most intensely grazed terrestrial systems — African grasslands — herbivores only consume about 66% of the above-ground plant biomass.9-21-102 While terrestrial plants produce subterranean structures such as roots, bulbs, and tubers that are generally inaccessible to most animals, most marine algae do not... 

Nicotine biosynthesis is localized in the roots of Nicotiana plants, and the alkaloids are transported to the shoots in the xylem stream,70 mainly to young leaves and stems and the reproductive parts of the plant.72 At first glance, the costly transport mechanisms seem to be a disadvantage, as there is a time lag of 10 hr from time of induction until the increase of nicotine production.73 The roots, however, as the site of synthesis are well protected against herbivory and continue the production, even when up to 88% of the total leave area is removed.74 Optimization of the cost-value ratio seems to be the reason for the inducible defense acting as a cost-saving... 

The experiments with extracts from various plant parts showed that the compounds responsible for inhibiting feeding on the plant occur practically in all parts of the plant, although the roots appear to be better protected against herbivory. In the course of this study, two natural products were identified as possible antifeedants in the crude root extracts, one of them being a novel compound, the diterpene gopherene diol. 

Neither translocation to roots nor root exudates explain the loss. A major part of the losses must be due to the shedding of various plant parts (pollen, flowers, leaves), leaching of nitrogen from aging leaves, and to herbivory these losses (except for windborne pollen) are mostly internal redistributions of the nutrient, as the litter, leaching, and herbivory return the nutrient to soils. But most of the nitrogen lost from tops of plants is due to volatilization of NHs. ... 

---