Effects of cages, plant age and mechanical clipping on plantain chemistry.
1994
Stamp N.E. | Bowers M.D.
In plant-insect herbivore field studies, effects of cages, plant age, and mechanical clipping on host plant chemistry are often postulated but not well documented. Effects of cages (for the purpose of restraining insects on experimental plots), plant age over the course of the experiment and mechanical clipping on plantain (Plantago lanceolata) chemistry. Leaf age affected the concentrations of nitrogen and iridoid glycosides (IGs; specifically aucubin and catalpol), with higher levels in newer leaves. Caged plants had higher levels of IGs and lower concentrations of nitrogen than uncaged plants. The IG concentrations were greater in new leaves of caged plants than uncaged plants, whereas the concentrations in mature leaves were unaffected by caging. Plants that were 5 weeks older had higher levels of IGs and lower nitrogen than plants harvested 5 weeks earlier. Comparison of three studies suggested that over the summer IG concentrations increase during dry years but decrease during wet years. Plants with above-ground parts clipped and then allowed to regrow for five weeks had similar concentrations of IGs and nitrogen compared to control plants; but the regrowth plants had a lower catalpol to total IG ratio. Cages and time can have significant positive effects on iridoid glycoside concentrations and significant negative effects on leaf nitrogen concentration. But the results also indicate that the direction and magnitude of the effects of cages, time and mechanical damage are not easily predicted.
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