Figure 6.
Microscopic observation of internal tissues sampled from different stages of male cones of transgenic PxL pine grafts carrying PrMC2pro-I-GUS or PrMC2pro-I-barnaseH102E. A, Image of tetrads from a GUS male cone at late stage 2.0 or early stage 3.0. The male cones were sampled on February 27, 2006, which is 1 week earlier than in B to D. B, Image of immature pollen grains of a GUS male cone at stage 3.3. C and D, Abnormal pollen development in barnaseH102E male cones at stage 3.3, with C showing enlarged tetrads with disorganized nuclear DNA and D showing degenerated tetrads. The magnification is 200-fold for all images.