Oat coleoptile

Other lipophilic weak acids have been shown to alter PD in plant cells. Benzoic and butyric acids (1 PM) rapidly depolarized the PD In oat coleoptile cells at pH 6.0 to about -100 mV (43). Higher concentrations (10 mM) of butyrate produced hyperpolarization. Butyrate also hyperpolarized apical cortical cells of maize roots... 

Fig. 2. Phototropic dosage response curves for oat coleoptiles at three intensities of blue light (440 nm) (7) 1.4 10-11, (2)...

If only the extreme apex of the oat coleoptile is irradiated unilaterally, curvature nevertheless develops normally, migrating down to the light shielded region (first positive curvature). This observation led to the demonstration by Boysen-Jensen in 191018), showing that the principle causing curvature could be transmitted across... 

Other orchid metabolites suchs as batatasin 1, inhibited the growth of liverworts, algae and oat coleoptiles. Batatasin 1 also inhibited the CO2 dependent O2 evolution and the flow of electrons from water to methylvi-ologen in spinach chloroplasts, and it inhibited the succinate-dependent O2 uptake in potato tuber mitochondria. Other phenanthrenes such as orchinol, which has a free hydroxyl at the 7-position, inhibit indole-3-acetic acid (lAA) oxidation catalyzed by horseradish peroxidase. 

Hydrolysis of oat-coleoptile walls yields173 the disaccharide GalA-(l— 2)-Rha, and small proportions of 2-O-methyl-D-xylose and 2-O-methyl-L-fucose, sugars characteristic of the rhamnogalacturonan II of dicots, have also been obtained from this source.62 However, if rhamnogalacturonan II is present in monocot cell-walls, it is present at a concentration of, at most, one-tenth of that in the walls of dicots. 

Cell-wall-bound enzymes in monocots have been less extensively studied than in dicots. Moreover, the majority of studies with this class of plants has been conducted with oat coleoptiles. 

D-galactosidase nor / -D-glucosidase plays an important role in shortterm growth promoted by auxin or acid in oat coleoptiles, Greve and Ordin245 purified, and characterized, the wall-bound a-D-mannosidase of this tissue. 

In contrast to these findings, a glucuronoarabinoxylan isolated from oat coleoptiles did not bind to cellulose in vitro under reaction conditions that allowed other heteroxylans to bind.53 This oat heteroxylan had, however, a high percentage of arabinosyl side chains that would be likely to hinder binding sterically. A similar inability to bind to cellulose is exhibited by an arabinose-rich arabinoxylan isolated from cultured, barley-aleurone cell-walls.61... 

There is much evidence that the hydroxy-L-proline-rich glycoprotein is involved both in the mechanical properties of the wall and in rates of growth. Cleland514 516 showed that, in oat coleoptiles, removal of wall... 

Instances of parallel responses in growth and synthesis have been found,83 38 but other studies have shown no synthesis response.28 33 Indole-3-acetic acid increased the incorporation of acetate-I4C and sucrose-,4C in the concentrated, alkali-soluble portion of oat coleoptiles,87 but this result could not be confirmed with labeled glucose38 or galactose.8 No increased... 

Subsequently, Ordin and Hall (25, 26) found that particulate preparations from oat coleoptiles could use UDP-D-glucose as substrate for polysaccharide formation. Upon degradation of the polysaccharide derived from UDP-D-glucose with impure cellulase, cellobiose, and to a lesser extent a substance identified as a trisaccharide containing mixed / -(1 - 4), / -(1 - 3) glucosyl linkages were obtained. 

Peas are a low-fat plant, and it is likely, therefore, that our results should not be freely extended to all other auxin- and gibberellin-induced systems. In fact, the equally classic oat coleoptile section hormone assay does not seem to respond to the fatty substances. Even the pea section fails to respond, unless the seedling has received some red light during the early part of its development. 

Bomoroni C. 1992. Synergism of action between indoleacetic acid (IAA) and diluted solutions of CaC03 on the growth of oat coleoptiles. Berlin J Res Horn 1 275. 

O Brien, T. P. and Thimann, K. V. 1966. Intracellular fibers in oat coleoptile cells and their possible significance in cytoplasmic streaming. Proc. Nat. Acad. Sci. 56, 888-894... 

The first plant bioassay [Avena sativa L (oat) coleoptile test] was employed by F.W. Went in the 1920 s to demonstrate the existence of and to quantitatively assess the first growth-modifying substance [indole-3-acetic acid (IAA)] isolated from plants.122 Plant bioassays have been extremely useful and intimately linked to the discovery and characterization of the major classes of plant hormones. In fact, many of the bioassays used now were developed for PGRs. Bioassays have been used to screen, evaluate phytotoxicity or plant growth promotion, study mode... 

A pentasaccharide and a trisaccharide have been isolated from an enzymic hydrolyzate of hemicellulosic material from oat coleoptiles.224 Methylation analysis of their structures indicated that these compounds may derive from j8-D-(l — 4)-linked D-glucans having terminal D-xylopyranosyl groups on some 0-6 atoms. Xylo-glucans having these structural features are present in the primary cell-walls of dicotyledons.22411... 

Figure 1. Effects of CaCl2 on bioassays for auxin, gibberellin, and cytokinin. A effects of CaCl2 on elongation of oat coleoptile sections in the presence and absence of indoleactic acid B effects on elongation of lettuce hypocotyls in the presence and absence of gibberellic add and C effects on enlargement of Xanthium cotyledon pieces in the presence and absence of benzyladenine (13).

PG has been found in seedlings of various plants including beans, corn, oats, and peas (Table III). In oat coleoptiles, the activity was highest near the growing tip and it decreased markedly as the distance from the tip increased. Similarly in pea seedlings, PG activity was highest in the plumules and hook, but the activity was quite high in the 1 cm section below the hook and considerably lower in lower sections of the epicotyl (57). However, PG was also found in stem and leaf tissues from these plants. 

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