Caulonema differentiation

Table 1. Caulonema differentiation with various auxins...

Fig. 1. Caulonema differentiation and medium pH changes in MMG and buffered MMG. Chloronema cells were cultured at an inoculum density of 0.1 mg ml in liquid medium. lAA was 2 jaM buffers were 15 mM, pH 5 sodium succinate and 25 mM, pH 6 sodium 8-glycerophosphate...

Table 2. Effect of applying lAA on PCIB-prolonged lag in caulonema differentiation ...

Most of the 2° chloronema and caulonema differentiated into rhizoids. 

The above experiment indicates that a limitation of nutrients (e.g. partial starvation) enhances caulonema differentiation in protonema growing on the agar surface. Similar enhancement is also obtained in auxin-free, nitrate-limited liquid medium. Under the latter conditions, in the presence of 0.5 to 2.5 mM nitrate, both caulonema and rhizoids were produced. Their formation is independent of inoculum size between 0.05 and 2.5 mg ml" The cells cultured at a high cell density (0.5 mg ml ) in the low nitrate medium (LNM, nitrate 1.5 mM) responded to 1 juM lAA (Fig. 5), while cells in the medium with adequate nitrate (MMG, nitrate 8.4 mM) responded very slightly to 3 fiM lAA. Upon buffering these media at pH 5, cells responded to lower auxin concentrations and caulonema differentiated at 10-30 nM lAA. The cells grown in LNM or MMG respond to more or less the same... 

Fig. 4. Differentiation of caulonema on solid MMG (nitrate at 8.4 mM) and low-nitrate medium (LNSM. nitrate at 0.5 mM). Protonema were grown on cellophane discs placed on the agar surface. Protonema were allowed to remain on the media (untransferred), or were transferred daily to fresh MMG or LNSM (transferred). Protonema stopped growing on MMG in the transferred set after 6 days (8% caulonema). while the control (untransferred) showed 40% caulonema. On LNSM protonema grow slowly, but caulonema differentiate more rapidly than on MMG...

Fig. 5. Differentiation of caulonema in response to lAA in liquid MMG and low-nitrate medium (LNM, nitrate 1.5 mM). Cells were cultured at an inoculum density of 0.5 mg mb and the media were buffered at pH 5. Caulonema were scored after 3 days. In MMG only caulonema differentiated while in LNM both caulonema and rhizoids were formed...

Fig.2A-C. Cell differentiation in auxin-free, MMG buffered at pH 5. Cells were cultured at an inoculum density of 0.05 mg ml in liquid medium. A Caulonema filaments 8 days after inoculation B conversion of 2 chloronemal apical cells into caulonemal apical cells in some of the filaments 3 days after inoculation C formation of rhizoids 12 days after the transfer of cells. Horizontal bars are lOO jam...

Caulonema and Rhizoid Differentiation in Nitrogen-Limited Medium... 

Fig. 4. Differential absorption spectra of arsenazo III solution surrounding caulon-ema cells incubated in BA minus solution surrounding caulonema cells with no BA added over time. Note decrease in absorption at 600 and 658 nm as compared to the isosbestic point at 572 nm arrows) indicating an uptake of Ca-" by cells incubated in BA that is greatest at 5 h after BA treatment...

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