Leaf primordia

Promotion of flowering (by irradiation during the night) in Chenopodium, Hordeum, Hyoscyamus Inhibition of flowering (by irradiation during the night) mLemna,Pharbitis, Xanthium Development of primary leaves and formation of leaf primordia in Sinapis Enzyme induction (phenylalanin-ammonialyase ascorbate oxidase) and repression (lipoxygenase) in Sinapis... 

At times when a plant needs to slow down growth and assume a resting stage (dormant), abscisic acid is produced in the terminal bud, which slows down growth and directs the leaf primordia to develop scales that protect the dormant bud during winter. Since the hormone also inhibits cell division in the vascular cambium, both primary and secondary growth is put on hold during winter. 

Description of type species Stromata 32.2-62.8 mm in length (diameter dependent on diameter of host culm), around culm, enclosing inflorescence primordia, leaf primordia and leaf sheath, cylindrical, first pallid, smooth and moist in appearance, covered with hymenial (conidial) layer, later yellow to orange and vermcose with emergence of perithecia. Hymenial layer composed of hypha-like conidiogenous cells,... 

D.J. Cosgrove. Cell wall loosening by expansins. Plant Physiol, 1998,118, 333-339 A.J. Fleming, S. McQueen-Mason, T. Mandel, C. Kuhlemeier. Induction of leaf primordia by the cell-wall protein expansin. Science, 1997, 276, 1415-1418... 

Fig. 4. Sections of (A) normal and (B) carngrass shoot apices at plastochron 15. The initiation of leaf primordia indicated by periclinal divisions (p.d.) in the first layer takes place at a distance from the level of insertion of the older primordia, indicated by the arrow, which is shorter in comgrass than in normal. The comgrass apex (B) is at its maximum size within the plastochron. X410. Preparations and photos made by Hermilo H. Angeles.

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