Efficient Regeneration of Carrot (Daucus carota L.) plants from cell suspension derived-callus

This study succeeded in establishment carrot cell suspension cultures from stem callus in liquidMS medium containing 1.0 mg L-1of each NAA and BA. Its density approach 3.4 ×105cell ml-1atthe third day of culture. These cells ,continued, when embedded in agar drop using MultipleDrop Array (MDA) technique, in division and forming cellular colonies which producingnumerous callus primordia that developed to callus cultures. When transferred to the soliddifferentiation medium (MS+ 1.0 mg L-1 NAA+ 1.5 mg L-1 BA), two hundreds and seventy-threeshoots produced. They readily rooted in agar-solidified MSO medium after three weeks andadapted in conditions of culture room. They were not transferred to field due to the unfavorableenvironmental conditions at that time. Cell suspension-derived callus tissues contained 82.62 μganthocyanin gm-1 of callus fresh weight, and 0.555 mg beta-carotene 100 gm-1of callus freshweight in the third period of extraction compared with their quantity calculated in stems calluswhich recorded 52.4 μg gm-1and 1.988 mg gm-1respectively.

Orientation of macromolecules in the walls of elongating carrot cells

When round cells from a carrot cell suspension culture are diluted into fresh medium without auxin, the cells elongate to almost 50 times their original diameter within three days. This process of elongation is accompanied by changes in both the composition and the orientation of cell wall polymers. We have obtained information on the orientation of wall polymers in elongating cells by two complementary techniques, one using microscopy and one spectroscopy. Images obtained by the fast-freeze, deep-etch, rotary-shadowed replica technique show that walls of round carrot cells have no net orientation of cellulose microfibrils, and that many thin fibres can be seen cross-linking microfibrils. Walls of elongated carrot cells, in contrast, show a marked net orientation of microfibrils at right angles to the axis of elongation. Fourier Transform Infrared (FTIR) spectra obtained from defined areas of single cell walls show that walls of round carrot cells contain more protein, esters and phenolics in a given area (10 microns × 10 microns) than walls of elongated carrot cells, that contain proportionally more carbohydrate. The orientation of particular functional groups, with respect to the direction of elongation of the cell, can be determined by inserting a polariser into the path of the infrared beam, before it passes through a cell wall sample mounted on the stage of the microscope accessory. In the walls of elongated cells, ester bands, amide bands characteristic of proteins, and stretching frequencies in the carbohydrate region of the spectrum all show a net orientation transverse to the long axis of the cells. In the walls of round carrot cells, however, there is no such net orientation of polymers. Spectra obtained from 25 microns-thick fresh sections of the etiolated stem of a carrot seedling show that different wall components are polarised in different tissue types. These techniques have therefore enabled us to define differences in both the composition and the architecture of walls of elongating cells at the level of a single cell, and to suggest that polymers not previously thought to be ordered, such as pectin and protein, are strictly oriented in some wall types.