Nitella

Green, P.B., Erickson, R.O. Buggy, J. (1971). Metabolic and physical control cell elongation rate in vivo studies in Nitella. Plant Physiology, 47, 423-30. 

Such a study has been performed on a model plant system, the Nitella flexilis cell wall [1, 2, 3]. This freshwater alga has giant intemodal cells whose easily isolated cell walls constitute a simplified model of higher plant cell walls it has no lignin and its pectin is not methylesterified. Isolated cell walls are cut in pieces and distributed in different lots over the whole exchange isotherm to reduce variability between experimental points. 

Fig. 1. The proportion of uronates that bind copper in the isolated Nitella cell wall is plotted as a function of the fraction of copper in a mixed solution of copper and calcium.

Since cupric ions are paramagnetic, it is possible by electron paramagnetic resonance (EPR) to obtain information on the status and the environment of the Cu ions adsorbed on uronic acids [4, 5]. Nitella cell walls with uronate charges compensated to 9 or 100% with copper in equilibrium with mixed copper and zinc chloride solutions had their EPR spectra recorded at two different temperatures, 93 and 293 °K (Fig. 3.a, b). 

Fig. 3. EPR spectra of Nitella flexilis cell walls with cupric ions on 9% (a) or 100% (b) of the uronates. The spectra have been recorded at two temperatures (arbitrary intensities). The sharp small peaks indicate g = 2.0028. ...

Mimosa pudica and insectivore type, Drosera rotundifolia, Dionaea muscipula, and the cells of algae Nitella and Char a [62,63],... 

Collander, R. (1954). The permeability of Nitella cells to non-electrolytes, Physiol. Plant., 7, 420-445. 

According to Claude Bernard the action of anesthetics is very general. They react not only with animals but also with plants. Bose has found that plants anesthetized with ether go through a preliminary period of increased irritability or stimulation. A dilute alcohol solution acted as a stimulant, whereas a concentrated alcohol solution acted as a depressant. Nichols applied chloroform to the wall of an intemode of Nitella by means of a capillary pipette. An area of non-motile protoplasm was produced at the point of application of the anesthetic. This area of non-motile protoplasm resumed its movements later, so the process appears to be a reversible one. Nichols considers the effect to be due to gelation, thus providing us with a case of reversible coagulation in plants accompanied by anesthesia of the part affected. 

The movement of glycosides and most of their hydrolytic products across the plasmalemma into the cell generally occurs by means of carriers associated with the plasmalemma. Without such carriers,- the plasmalemma is effectively impermeable to sugars25 but some molecules, such as methanol,250 may enter cells by simple diffusion, as described for the stoneworts (algae) Chara australis and Nitella translu-cens.26... 

An impressive demonstration that myosin heads do move along the actin filaments was provided by Sheetz and Spudich, who found that myosin-coated fluorescent beads 0.7 pm in diameter will move along actin filaments from cells of the alga Nitella in an ATP-dependent fashion at velocities similar to those required in muscle.149 The myosin heads literally glide along the thick cables of parallel actin filaments present in these algae. 

In 1972, Williamson43 used two organisms, Chara corralina and Nitella translucens, to examine the effects of CB on cytoplasmic streaming. Whole cells from rhizoidal and small leaf internode tissue were treated with the metabolite at concentrations of 1-50 pg/mL in dimethylsulfoxide (DMSO). There was a concentration, time dependent result so that 50 pg/mL inhibited streaming in a few minutes, whereas it took 6 h to induce the same effect with 1 pg/mL. Washing the cells with a DMSO solution, used at the same concentration in which the CB had... 

Chen, J. C. W. 1973. Observations of protoplasmic behaviour and motile protoplasmic fibrils in cytochalasin B treated Nitella rhizoid. Protoplasma 77, 427-435... 

Nagai, R. and Rebhun, L. 1966. Cytoplasmic microfilaments in streaming Nitella cells. J. Ultrastruct. Res. 14, 571-589... 

For these experiments, they used a more well-defined method for attaching the myosin to the beads. The beads were clumps of killed bacterial (Staphylococcus aureus) cells. These cells have a protein on their surface that binds to the Fc region of antibody molecules (Fig. 5-2la). The antibodies, in turn, bind to several (unknown) places along the tail of the myosin molecule. When bead-antibody-myosin complexes were prepared with intact myosin molecules, they would move along Nitella actin fibers in the presence of ATP. 

Spudich and colleagues prepared bead-antibody-myosin complexes with varying amounts of myosin, HMM, and SHMM, and measured their speeds along Nitella actin fibers in the presence of ATP. The graph below sketches their results. 

Figure 1-15. Schematic sections of a hypothetical cylindrical cell resembling the intemodal cells of Nitella or Chora, illustrating various dimensions, the hydrostatic pressure, and the stresses existing in the cell wall (a) section perpendicular to cylinder axis, and (b) section through cylinder axis. The colored region indicates an aqueous solution where the hydrostatic pressure P leads to the longitudinal stress trL, which acts in an annulus of area approximately equal to 2nr x f , and the tangential stress crT, which acts along the two sides each of area l x tcw.

To estimate the magnitudes of the stresses and the resulting strains in the cell wall, let us consider a Nitella or Chara cell that is 1 mm in diameter with a cell wall that is 5 pm thick. In this case, rtf91 is... 

A cylindrical Nitella cell is 100 mm long and 1 mm in diameter, a spherical Valonia cell is 10 mm in diameter, and a spherical Chlorella cell is 4 im in diameter. 

C. If it takes 1 s for the internal concentration of ethanol, which is initially absent from the cells, to reach half of the external concentration for Chlorella, how long would it take for Nitella and Valonia Assume that ethanol is the same for all of the cells. 

D. Assume that the cell walls are equal in thickness. For a given internal pressure, which cell would have the highest cell wall stress (consider only the lateral wall for Nitella) ... 

Kamiya, N., Tazawa, M., and Takata, T. 1963. The relation of turgor pressure to cell volume in Nitella with special reference to mechanical properties of the cell wall. Protoplasma 57 ... 

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