Ultrastructural and biochemical development of the photosynthetic apparatus during callus induction in carrot root explants

Abstract

During the first 8-12 days of cultivation in a nutrient solution containing IAA, inositol and kinetin freshly isolated carrot root explants develop into a chlorophyllous and photosynthetically active tissue culture. Electron microscopy, low temperature pigment absorption spectra and fluorescence induction profile recording as well as the determination of the activity of some enzymes (ribulosebisphosphate carboxylase, phosphoenolpyruvate carboxylase) and CO2-fixation experiments were carried out. Based on the results, a sequence of developmental stages of the photosynthetic system will be proposed. During the autotropic period from about the 20th day of culture onward the light reaction system of these tissue cultures is quite comparable to that of carrot leaves; however, some differences in the CO2-fixation mechanism were observed.

Growth regulation, plastid differentiation and the development of a photosynthetic system in cultured carrot root explants as influenced by exogenous sucrose and various phytohormones

“…Sucrose again induced heavy starch accumulation in addition to the formation of thylakoids ( Figure 2D). In these treatments stacking of thylakoids was somewhat more advanced after 12 days, and reached stage 3 to 4 of chloroplast development (see 13). The biophysical parameters also indicate the development of photsynthetic units.…”

“…The most important factors are light, nutritional status and hormonal supply. Although several autotrophic cultures of green cells have been reported (22), a sugar supplement is usually needed in the medium for maximal growth of cells [6,[11][12][13][16][17][18]. However, a sucrose supplement to the nutrient solution usually decreases chlorophyll content and activity in CO2-fixation [16,17].…”

“…For electron microscopic investigations samples were fixed in Os04 followed by Glutaraldehyde both in sodium cacodylate buffer pH 6.8 (for details see ref. 13). For methods to determine fluorescence induction and low temperature spectra see also [13].…”

“…13). For methods to determine fluorescence induction and low temperature spectra see also [13]. Plastid countings were made by changing focus on the cells prepared from the periphery of the explants by gentle smearing, taking precautions to keep the number of damaged cells at a minimum.…”

Aspects of Photosynthetic Plant Tissue Cultures

“…All three systems allow the plastids a relatively slow transition compared to that seen with etiolated whole plant tissue. Before greening the plastids almost ~lways contain a large amount of starch and few if any lamellae (21,25,42,43,44,45). One wonders if the large starch content obscures the lamellae which might exist in two of these reports (44,45).…”