Source ⁄ sink relationships
Cytokinins are important regulators of plant growth and development
(Ma, 2008) and have been shown to control plant
source ⁄ sink relationships (Roitsch and Ehneß, 2000). The effect
of IPT expression and the concomitant CK synthesis (Rivero
et al., 2007) on sink strength was tested by analysing the contents
of mineral-nutrients and the quantification of sucrose and
starch in the grain. Electron microscopy sections of flag leaf
parenchyma cells showed that under WW conditions, the transgenic
plants had a higher number of starch granules than the
WT plants, and this difference was not seen under WS (Figure
6a). The starch content of the flag leaves from the transgenic
plants was significantly higher than that of the WT plants
(58% and 88% for WW and WS treated transgenic plants,
respectively). A similar pattern was seen in the mature grains,