Cotyledons control

Cucumber cotyledons were inoculated with purified tobacco mosaic virus (TMV) 20 to 24 hours before vacuum infiltration with different concentrations of crude water extracts of plant leaves (4). After 7 days, inoculated leaves were harvested and stored 24 hours in the dark in a moist chamber to remove excess starch. Starch lesions were counted after clearing with alcohol and staining with an iodine-potassium iodide-lactic acid mixture. The inhibitory effects of various extracts were demonstrated by comparing lesion counts of treated cotyledons to counts on control cotyledons. 

Cotton plants were exposed to 1 ppm ozone for one hr and 40 discs were cut from two cotyledons of two plants for uptake of l C-UL-d-glucose (4 hours). Each exposed value represents three determinations and each control value represents six determinations. 

Cellular leakage as determined by changes in conductivity of treatments minus control conductivity changes of cucumber cotyledons as affected by exposure to different DHZ concentrations. Error bars are + 1 SE of the mean of six plates 50 pM acifluorfen used as positive control. Tissues were incubated in solutions in darkness for 18 h and then exposed to light. (From Galindo, J. C. G. etal. 1999, Phytochemistry 52, 805-813. With permission.)... 

Figure 2. Effect of sequential, weekly culture transfer on sicklepod control by Alternaria cassiae grown on V-8 agar (5Z) Spores were harvested from plates in a solution of 0.02% (v/v) Sterox NJ surfactant. Sicklepod plants in the cotyledon to 1-leaf growth stage were inoculated with A. cassiae spores (10 spores/ml), then subjected to a 6-h dew period at 25° C. Sicklepod plants were evaluated 14 days after inoculation.

Modulation of paraquat toxicity with the mixed-valence complex of penicillamine also involves the prevention of lipid peroxidation [637, 638]. Chloro-plast fragments of flax cotyledons had fatty acids that were closer to non-treat-ed control levels than paraquat-treated plants. Decreases in chlorophyll, carotenes and xanthophyll produced by paraquat were also prevented by treatment with the mixed-valence complex. These protective effects of this... 

We have tried to circumvent these problems by isolating a cotyledon of the placenta and perfusing its umbilical circulation in situ with blood of known and accurately controlled flow rates and 02 tensions (47). We have also varied maternal arterial Oo tension by administering various concentrations of inspired 02. 

N. plumbaginifolia cell culture and seedlings [14,72]. These studies indicate some control of the signaling pathway by protein phosphorylation but do not directly demonstrate the involvement of phosphorylation as signaling steps. Cytokinin induction of msrl may be related to the control of cell division either in N. plumbaginifolia cell cultures [72] or in the cotyledons of the cytokinin hypersensitive mutant zeaS.l [14]. 

Figure 8. The chlorophyll content of paraquat-treated flax cotyledons incubated in the presence or absence of copper-penicillamine (PA-Cu) under light of 5.25 Wm. The final concentration of paraquat was 10 M and the PA-Cu represented 50 units of super oxide dismutase. Key control, JH paraquat plus PA-Cu, A ...

In our experiments, limited protection of AFM-induced injury to cucumber cotyledons was obtained with BHA and BHT. These two compounds showed some synergistic characteristics. However, the concentrations necessary for protection were high (400 yM) and caused some injury to the controls. The concentrations of BHA and BHT needed to protect the tissue should be higher than for a-T. BHA and BHT each have an antioxidant stoichiometric factor (n) equal to 1, whereas for a-T, n can be equal to 2 (67). An n of 2 for a-T means this molecule has the ability to quench up to 2 radicals before being destroyed. DPPD has been reported to have antioxidant activity (68). However, in our tests DPPD was toxic at high concentrations (400 yM) and ineffective at lower concentrations (e.g., 50 yM),... 

Figure 4. Efflux of from cucumber cotyledons treated with 1 fxM AFM in the presence of various concentrations (0, 50,100, and 200 /xM) of aAocopherol (3). A t time zero, cotyledons were exposed to herbicide and a-tocopherol in the dark in a nitrogen atmosphere. After 1 h, the atmosphere was changed to air and at 2 h the cotyledons were exposed to light (600 fxE/m s, PAR). Closed circles are effluxes from control tissue treated with 1.0% ethanol or 1.0% ethanol plus 200 fM...

Some laboratories (64 M) have found PChlide to be the primary porphyrin to accumulate in diphenyl ether-treated tissues. In our green cucumber cotyledon disc system, we have found only PPIX levels to be increased by these herbicides (67), however, in intact cucumber seedlings (Fig. 5) and tentoxin-affected cucumber cotyledon discs ( S) we found diphenyl ether-enhanced PChlide levels. PPIX levels accumulate to many (as much as several hundred) times the control levels in herbicide-treated tissues, whereas the maximum PChlide accumulation is only four-fold that of the control. Since the metabolic block is at Protox, there is no inhibition of conversion of PChlide to Chi after exposure to light. Therefore, it seems unlikely that PChlide plays a significant part in the mechanism of action of these herbicides. Indeed, of the Chi precursors assayed, only PPIX significantly correlated with herbicidal damage caused by a several different acifluorfen/DP/ALA treatment combinations ( 7). No significant correlations were found with accumulated PChlide,... 

The erucic acid content is largely controlled by the genotype of the developing seed rather than by the genotype of the maternal plant (Downey and Harvey, 1963 Harvey and Downey, 1964 Stefansson and Hougen, 1964 Kondra and Stefansson, 1965). For this reason, a technique could be developed whereby one cotyledon or a part of one cotyledon could be used as a sample for fatty acid analysis, while the remainder of the seed could be used to produce a plant (Downey and Harvey, 1963). This technique is useful in breeding and can also be used to facilitate genetic studies, since the seeds on an Fi plant represent the F2 population. 

The effect of the Pms elicitor on the activities of phenylalanine ammonia-lyase (PAL) and FS after exposure of wounded soybean cotyledons to the elicitor is shown in Fig. 3 (Ref. 9). The specific activities of PAL and PS showed large increases with mmriitiiim values after about 20 h for PAL and 20-30 h for PS. The decline in specific activity was more rapid for PAL than for FS. Notably, control wounded cotyledons with elicitor omitted produced neither measurable amounts of glyceollin nor significant Increases in the activities of the two enzymes tested. 

Fig. 3. Time course of changes in the elicitor-induced activities of PAL and FS in wounded soybean cotyledons. Sets of cotyledons were incubated at saturating elicitor concentrations (Fig. 2) and the enzyme activities measured at various intervals after elicitor application ( fA) (Ref. 9). Open symbols (o,a) represent control wounded cotyledons with elicitor omitted.

FIGURE 2 A-C. In-vitro translation of compartment-specific phosphorylase forms. A In-vitro translation of mRNA isolated from cotyledons of germinating seeds. Immunoprecipitation was performed using anti-cytosolic (lane a) or anti-plastidic (lane b) phosphorylase-IgG. Lane c preimmune control. The position of the mature cytosolic (CP) and plastidic (PP) enzyme form is marked. B Immunoprecipitation in the presence of an excess of purified cytosolic (lane b) or plastidic (lane c) phosphorylase. Lane a no addition. Immunoprecipitation was performed using anti-cyto-solic phosphorylase IgG. Details as in 2 A lane a. C Processing of the precursor of the plastidic phosphorylase form by a stromal fraction of isolated chloroplasts. For details see text. pPP Precursor of the plastidic enzyme CP cytosolic enzyme form... 

Fig.3 Photoconversion of gathered cotyledons ( ) and intact plants ( 0 ) esterification of gathered cotyledons ( 0 ) and intact plants ( ) percentages are related to H2O dark control 7.4 nmol/g fw pchl(ide)...

Fig.4 Total pigment content after flash irradiation of gathered cotyledons related to corresponding dark control (pchl(ide) in nmol/g fw) H2O 7.4 2 2 12.8 8H 9.9 ...

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