Figure 1.

Effects of BFA on pollen germination and pollen tube morphology. A, Healthy P. meyeri pollen tubes cultured in standard medium for 36 h, showing good germination and many long pollen tubes with normal shape. B, P. meyeri pollen tubes cultured in medium containing 5 μg mL⁻¹ BFA for 36 h, showing poor germination and a few short tubes with morphological abnormalities. C, Micrograph of a control P. meyeri pollen tube cultured for 20 h, showing a regularly shaped pollen tube of constant diameter and a clear zone at apical region. D to F, Typical examples of pollen tubes in the presence of BFA for 20 h. D, Pollen tube incubated in 1 μg mL⁻¹ BFA; stars indicate changes in growth direction (wavy pattern). E, Pollen tube incubated in 5 μg mL⁻¹ BFA, showing a swelled tube tip (arrowhead). F, Most of the pollen grains cultured in 8 μg mL⁻¹ BFA, showing aberrant protrusions, which were not regarded as germinated. G, Details of cell wall structure in control pollen tube. The cell wall was uniform, compact, and 0.4 μm thick. H, Details of cell wall structure in BFA-treated pollen tube. The cell wall became more loosely packed, showing the cell wall thickness from 0.35 to 0.6 μm in the presence of BFA. cz, Clear zone; CW, cell wall. Bars in A and B = 100 μm; in C to F = 50 μm; and in G and H = 0.3 μm.