Factors determining the distribution of the aphid sipha kurdjumovi on grasses
1974
DIXON, A.F.G.
J. W. SHEARER Sipha kurdjumovi Mordwilko prefers to settle on the concave upper surfaces of the leaves of barley seedlings, and inserts its stylets mainly through stomata to gain access to and pierce the phloem elements, Stomata. are absent from the stems of barley seedlings but are present on the leaf, more abundantly on the upper surface. Phloem elements are closer to the lower than to the upper leaf surface. Reversing the curvature of a leaf results in significantly more aphid s settling on the under-surface of the leaf. However, the aphid still does not show a preference for the lower surface even though this is now the concave surface. Offered flattened leaves of barley, the aphid prefers to settle on the upper surface, which is more prominently ridged than the lower surface. However, when allowed to settle on flattened leaves of Poa annua L., where there are no pronounced ridges, S. kurdjumovi settles in equal numbers on both surfaces of the leaf.
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