Algae Chaetomorpha Research Articles

PHOTOSYNTHETIC CAPACITIES AND BIOLOGICAL STRATEGIES OF GIANT‐CELLED AND SMALL‐CELLED MACRO‐ALGAE

SummaryData are presented which show that the photosynthetic and respiratory characteristics of the giant‐celled alga Chaetomorpha darwinii are those of a shade plant (denned physiologically in terms of rates of photosynthesis at light and inorganic carbon source saturation, and the irradiance required to saturate photosynthesis and to compensate respiration by photosynthesis). This is in agreement with previous suggestions that giant‐celled algae have the characteristics of ‘shade plants’, while small‐celled macroalgae can be either ‘sun plants’ or ‘shade plants’. A comparison of giant‐celled algae with small‐celled macro‐algae in terms of ecological strategies has been made, using previously published data on Enteromorpha intestinalis, Chaetomorpha linum (‘fugitive’small‐celled), Chaetomorpha darwinii, Hydrodictyon africanum (‘stressed’ giant‐celled), Cham corallina (‘canopy‐dominant’/‘stressed’ giant celled) and Laminaria digitata (‘canopy‐dominant’ small celled), as well as new data on net and mass spectrometric measurements of O2 exchange in L. digitata. It is suggested that the ability of giant‐celled algae to compete as ‘canopy dominants’ may be related to cytoplasmic streaming in the ‘absence of many (or any) plasmodesmatal barriers to diffusion providing an efficient means of long‐distance transport in a differentiated plant, as an alternative to phloem‐type translocation in small‐celled ‘canopy dominants’. The significance of the giant‐celled habit in ‘stressed’ macroalgae is not clear, although the absence of giant‐celled algae from the ‘fugitive’ category may be related to their limited capacity for rapid growth relative to small‐celled algae.

Cell turgor and selective ion transport of Chaetomorpha linum

The littoral alga Chaetomorpha linum is especially able to maintain a constant turgor pressure in the cell by regulating the internal osmotic pressure, if the salt content of the sea water changes. Experiments in artificial isotonic sea water with a constant sodium concentration, but variable potassium concentrations (from 1 to 50 mMol/1) prove, that the decrease or increase of the potassium concentration in the medium (CK a) is an essential cause for this regulation of the turgor pressure besides the change of the osmotic pressure of the medium, which was thought to be the predominant cause till now. In the examined concentration range the ratio CK a to CK 1 (potassium concentration in the cell) depends linear on CK a in the steady state. At low values of CK a (< 10 mMol/1) the decrease in CK 1 is compensated by a reversible sodium uptake only in part, and this leads to partly high changes in the cell turgor pressure, although the osmotic pressure of the medium remains constant. The results are discussed on the basis of carrier models.

Effects of potassium concentration and osmotic pressure of sea water on the cell-turgor pressure of Chaetomorpha linum

The unicellular littoral alga Chaetomorpha linum is especially capable of maintaining its cell-turgor constant by regulation of the internal osmotic pressure, when the salinity of the sea water is altered. The decrease or increase of the external potassium concentration is seen to be an important cause of this turgor regulation, as well as the alteration of the external osmotic pressure, which was already known to be an important factor. This has been shown by experiments in artificial sea water with reduced osmolality and variable potassium concentration (1 to 50 mMol/l).

Phenolic Compounds in Wheat Flour and Dough

In the large coenocytic cell of the marine green alga Chaetomorpha darwin ii, the electric potential difference, .pvo, between the vacuole and the outside seawater can have either of two distinct states, a positive, and more usual state, with .pvo = +5 mY, and a negative state with .pvo = - 29 m V. The p.d. across the plasmalemma of the cell was approximately -72 mY, and the difference between the positive and negative states occurred at the tonoplast with .pvc = + 77 m V or + 43 m V respectively. In the change from the positive state to the negative state, the electrical resistance of the plasmalemma increased from 510 to 750 n cm2 , and the resistance of the tonoplast increased from 4900 to 7100 n cm2

Ionic Relations of Marine Algae III. Chaetomorpha: Membrane Electrical Properties and Chloride Fluxes

In the large coenocytic cell of the marine green alga Chaetomorpha darwin ii, the electric potential difference, .pvo, between the vacuole and the outside seawater can have either of two distinct states, a positive, and more usual state, with .pvo = +5 mY, and a negative state with .pvo = - 29 m V. The p.d. across the plasmalemma of the cell was approximately -72 mY, and the difference between the positive and negative states occurred at the tonoplast with .pvc = + 77 m V or + 43 m V respectively. In the change from the positive state to the negative state, the electrical resistance of the plasmalemma increased from 510 to 750 n cm2 , and the resistance of the tonoplast increased from 4900 to 7100 n cm2

Preliminary investigation of algal cellulose I. X-ray intensity data

X-ray intensity data have been collected for the cellulose in the cell wall of the filamentous green alga Chaetomorpha melagonium in order to attempt a closer definition of the structure of this cellulose and to make comparisons with the known data from ramie cellulose. There are significant differences of intensity between these two sets of data indicating structural differences over and above the number of chains within the unit cell. The unit cell parameter of C. melagonium cellulose, deduced with the aid of a computer programme using all the spacings and indices as data, are: a = 16.43 A ̊ b ( fibre axis) = 10.33 A ̊ , c = 15.70 A ̊ , β = 96°58′ . There are no zero layer plane reflections corresponding to this superlattice, indicating that in base plane ( ac) projection each of the Meyer-Misch sub-cells which make up the superlattice are identical. Moreover all the equatorial reflections can be indexed on a one-chain unit cell suggesting that every single chain has the same equatorial projection. On these grounds eight possible eight-chain unit cells are suggested each containing sheets of chains in the same sense alternating with sheets of chains of opposite sense. Calculated intensities match the observed meridional, zero and even-order layer plane reflections but no reasonable fit has been obtained for the first and third layer planes. The unit cells presented assume both that each chain in the unit cell has the same environment and that relative rotation of the chains is excluded. Much richer X-ray diagrams than any so far obtained will be necessary if these restrictions need to be removed.