Characteristics of the phloem and the cortex

The tangential arrangement of sieve tube/parenchyma bands is characteristic of all shrub species (Figs. 19-21 and 23). Often they contain a few sclerenchyma fibers (Figs. 20 and 21). One to several bands can be formed in one year. Distinct ray dilatations have been observed only on Berberis empetrifolium di

(Fig. 23). The phloem of the hemicryptophyte Epimedium al-pinum consists of small vascular bundle like groups (Fig. 22). A few Berberis and Mahonia species contain prismatic crystals in the rays.

Fig. 21. Phloem with tangential sieve-tube/ parenchyma layers with a few sclerenchyma fibers in the sieve-cell zone and sclerenchy-ma-cell groups in the rays. The cortex begins with large thin-walled cells. Stem of a 1 m-high shrub, dry rock, arid zone, Moab, Utah, USA. Mahonia fremontii, transverse section.

Fig. 19. Phloem with tangential sieve-tube/ parenchyma layers. Stem of a 1.5 m-high, evergreen shrub, hill zone, Botanical Garden Basel, Switzerland. Mahonia bealei, transverse section.

Fig. 20. Phloem with tangential sieve-tube/ parenchyma layers with a few sclerenchyma fibers in the sieve-cell zone. Phloem cells are mostly collapsed. Stem of a 1.5 m-high evergreen shrub, garden, hill zone, Bir-mensdorf, Switzerland. Berberis julianae, transverse section.

Fig. 21. Phloem with tangential sieve-tube/ parenchyma layers with a few sclerenchyma fibers in the sieve-cell zone and sclerenchy-ma-cell groups in the rays. The cortex begins with large thin-walled cells. Stem of a 1 m-high shrub, dry rock, arid zone, Moab, Utah, USA. Mahonia fremontii, transverse section.

di with, callus

Left Fig. 22. Phloem and cortex. Sieve tubes are collapsed (dark red). Outside the phloem are groups of sclereids. The cortex consists of thin- and thin- to thick-walled parenchyma cells. Rhizome of a hemic-ryptophytic herb, garden, hill zone, Bir-mensdorf, Switzerland. Epimedium alpi-num, transverse section.

Right Fig. 23. Phloem with tangential sieve-tube/parenchyma layers with a few sclerenchyma fibers (red, thick-walled cells) in the sieve-cell zone. Phloem cells are mostly collapsed. Rays are intensively dilated and partially filled with thin-walled callus cells. Stem of a 70 cm-high shrub on volcanic rocks, subalpine zone, Patagonia, Argentina. Berberis empetrifolium, transverse section.

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