Seedling growth inhibition

Our research focused on some possible modes of action of hydroxamic acids. Thus, experiments were performed in plants and seedlings of L. sativa and membrane permeability correlated with an inhibition in mature plant growth or in cell cycle progression related to a seedling growth inhibition. 

DIBOA was quantified and purified. Phytotoxicity was compared in bioassays for germination and seedling growth inhibition against weeds and tomato with P-phenyl-lactic acid (PLA) and P-hydroxybutyric acid (HBA), two previously identified and known phytotoxins from rye. Both DIBOA and BOA were consistently more toxic than PLA and HBA (Barnes Putnam 1987). 

Whole plant (or seedlings) Growth inhibition Weight, height, etc. 

Essential oils are known to have detrimental effects on plants. The inhibitory components have not been identified, but both alde-hydic (benzol-, citrol-, cinnamal-aldehyde) and phenolic (thymol, carvacol, apiol, safrol) constituents are suspected. Muller et al. (104) demonstrated that volatile toxic materials localized in the leaves of Salvia leucophylla, Salvia apiana, and Arthemisia californica inhibited the root growth of cucumber and oat seedlings. They speculated that in the field, toxic substances from the leaves of these plants might be deposited in dew droplets on adjacent annual plants. In a subsequent paper, Muller and Muller (105) reported that the leaves of S. leucophylla contained several volatile terpenes, and growth inhibition was attributed to camphor and cineole. 

Miscellaneous Identified Inhibitors. 3-Acetyl-6-methoxy-benzaldehyde is present in the leaves of the desert shrub Encelia farinosa. It is apparently leached from the leaves and washed into the soil by rain. Concentrations of approximately 0.5 mg. per gram of dried leaf material have been measured. In sand culture studies, growth of tomato seedlings was inhibited by 50 p.p.m. while 115 p.p.m. reduced growth by 50% (53). A concentration of 250 p.p.m. killed the test plants within one day. The structure was confirmed by synthesis, and the synthetic material was shown to be as active as the natural product (54). Derivatives were also prepared in which a cyano, nitro, or amino group was substituted for the aldehyde moiety. The amino derivative was reported to be the most highly toxic. 

Psilotin (R 0-D-glucose) Psilotinin (R=H) o o / o Psilotun nudum and IVesiperis tannensis Inhibits seed germination and seedling growth... 

Sick soil" toxicants Accumulation of toxicants from previous inhabitants evidently results in growth inhibition of roots and interfere with seedling establishment (46). 

Figure 1. Linear regression plot of tomato and radish seedling root growth inhibition with varying concentrations of phenyl aliphatic acids. Benzoic acid (V) phenylacetic acid (X) 3-phenyIpiropanoic acid (A) 4-phenylbutanoic acid ( ) trans-cinnamic acid (----) (1).

Figure 2. Linear regression plot of root growth inhibition of tomato and radish seedlings by o and -hydroxyphenyl) acids. o-Hydroxycinnamic acid, (o-hydroxyphenyl) acetic acid ( ) melilotic acid, 2-(o-hydroxyphenyl) butanoic acid ( ) o-hydroxy-benzoic acid, ( -hydroxypheny 1 )acetic acid (0) -hydroxycinnamic acid, =hydroxybenzoic acid, 3-( -hydroxyphenyl) propanoic acid (X) o-coumaryl glucoside, water control (----) (1 ). ...

Abdul-Wahab and Rice (9) found that boiling water extracts of johnsongrass leaves inhibited germination and seedling growth of several bioassay species at concentrations 80 times that used in this present study. 

Figure 3. Histograms showing growth response of cress, barnyard grass, and cucumber to 347 microbial isolates bioassayed on solid medium. Growth response 1) seedling growth minimal or germination nil, 2) pronounced inhibition, 3) slight inhibition, 4) growth comparable to controls, 5) stimulation over controls.

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