Inflorescence Initiation and Leaf Size in Some Gramineae

The morphology of successive leaves on the flowering shoot was studied in species of Glyceria, Lolium, and Triticum. The blades of successive leaves were progressively longer, eventually reaching a maximum, after which the blades of the last few leaves produced before heading were shorter. When the longest leaf blade was elongating, dissection of the shoot apices showed that inflorescence initiation was taking place. Epidermal cell measurements in Triticum indicate that differences in blade length are due to differences in the amount of cell extension. It appears that a correlated change occurs in blade morphology associated with the onset of the reproductive state of the shoot apex, brought about via changes in the amount of cell extension. A study of the effect of different amounts of low-temperature and different day-lengths on the relation between inflorescence initiation and the production of the longest leaf blade showed that, under some conditions, this relation can be disturbed.