Effect of leaf age on dsRNA extraction
Tissues extracted with formate buffer and ammonium sulfate
Note preferential extraction of smaller RNAs from lower leaves. This pattern is characteristic of incomplete extraction although it could reflect actual dsRNA concentration. Neither increasing buffer concentration nor formic acid concentration improved extraction of larger RNAs from "old" tissue.
Subsequent findings: RNA pattern from old (bottom) leaves is fairly reproducible. It's independent of grinding time. These factors suggest that the dsRNA pattern of old leaves is intrinsic (rather than an extraction artifact)