Petiole growth

Fertilization generally is used very sparingly in coastal vineyards. No real correlation between fertilization and crop response has been determined. Cook (2) indicated that vine requirements were determined best by leaf petiole analyses. Excessive fertilization resulting in vigorous vine growth must be avoided, however, as this may affect berry set and thus reduce crop. Mountain vineyards often are fertilized to assure a good covercrop for erosion control. 

Plant Growth Regulator absorbed by the leaves which stimulates formation of an abscission layer between the plant stem and leaf petioles, causing dropping of the entire green leaves... 

The axenic plants (shoot culture) of G. thunbergii were obtained by the same method as above (see 2.2.1). The petioles were cut off from the shoot culture and used for the explants for the direct infection with A. rhizogenes A4. The bacteria was applied by a needle to the cut ends of the petioles and, 2-3 weeks after inoculation, several hairy roots appeared at the infected sites. The hairy roots, after elimination of the bacteria on 1/2 MS solid medium containing an antibiotic (Claforan ), were transferred and maintained in hormone-free 1/2 MS and B5 liquid media in the dark at 25"C. Among 20 clones of the hairy roots, one clone which showed the fastest growth was used for the experiment. 

Although roots were generated from the petiole segment after the infection with Agrobacterium rhizogenes ATCC 15834, the growth of the excised bacteria-free roots on HE solid medium was slower compared... 

Fig. 3. Distinguishing characteristics of Toxicodendrons useful for field identification [33]. (1) Buds are not terminal, causing new directions of growth each season. (2) The petiole is enlarged at the point of attachment. (3) U- or V-shaped leaf scars. (4) Flowers, fruit on panicles in axillary position. (3) Trichomes on fruit of poison oak and some ssp. of poison ivy. (6) Exocarp which peels away in the winter. (7) After losing exocarp, fruits are smaller and chalk white with tiny black lines like longitudinal lines on a globe. (8) Empty fruit stalk, (g) Lenticels give a characteristic texture to the wood...

There is evidence that the growth of petioles is dependent on auxin from the blade. Blade removal in Helianthus inhibits petiole elongation about 90%, an effect which is partially overcome if auxin is supplied to the cut surface of the petiole (Palmer 1972). Application of auxin to either the upper or lower surfaces of debladed petioles causes an increase in growth rate. Dayanadan et al. (1976) have found that auxin, but not GA or kinetin, promotes cell elongation in parenchyma, collenchyma and vascular elements of the sheath pulvinus of Avena leaves. 

---