Germination of seeds

Unidentified Stimulators. Growth-inhibitory materials in, or secreted by, plants have for the most part been emphasized in this paper. However, root secretions of many plants also contain constituents required for the germination of seeds of angiospermous root parasites (Striga, Orobanche, Alectra, and Sopubia genera). This phenomenon has been reviewed by Brown (17). Striga asiatica was identified for the first time in the western hemisphere in 1956 in two... 

Experiment II. Volatile compounds from leaves and bulbs Volatiles (terpenoids, ethylene and other compounds) can be released from the leaves and other plant parts and consequently can affect the germination of seeds, growth and development of neighbouring plants in ecosystems. 

Adverse effects of paraquat in sensitive species of terrestrial plants and soil microflora have been documented at application rates of 0.28 to 0.6 kg/ha (death, inhibited germination of seeds, reduced growth), at soil concentrations of 10 to 25 mg/kg (growth inhibition), and at soil-water concentrations as low as 1.6 mg/L (reduced growth, inhibited synthesis of protein and RNA). Among terrestrial invertebrates, certain species of mites were sensitive to paraquat at recommended rates of application, and the sensitive honey bee died when its diet contained 100 mg/kg. However, paraquat in soils was not accumulated by earthworms and other species of soil invertebrates after applications up to 112 kg/ha. These points, and others listed in this section, are discussed in greater detail later. 

The effects of sulfur dioxide on cone production have been described by Scheffer and Hedgcock and Pelz. Generally, the decrease in tree vigor caused by the pollutant may eliminate or lower the frequency of cone production and diminish the size, weight, and germination of seed. The effects of chronic ozone injury on conifer seed production may be similar, in that tree vigor is drastically reduced. The effects of chronic ozone injury on ponderosa and Jeffrey pine seed production are under investigation by Luck (in Kickert et al,... 

Scandium sulfate [Scj(SO )j] 2Sc + 3SO —> Sc lSO l This compound is used in the germination of seeds for agricultural plants. 

Agami, M. and Waisel, Y. (1988). The role of fish in distribution and germination of seeds of the submerged macrophytes Najas marina and Ruppia maritima. Oecologia 76,83-88. 

Swank, W. (1944). Germination of seeds after ingestion by ring-necked pheasants. Jottmfll of Wildlife Management 8,223-231. 

The second example described here is dormant seeds from Rosa canina. Extracts of these seeds also inhibit germination of seeds of several plants (10). In Figure 5 a scheme is given for extraction and separation oF"three different inhibitor compounds. All these are present in the acid fraction. The first essential step is chromatography on Sephadex LH-20, which separates inhibitor I from inhibitor II and III. Inhibitor I was identified as abscisic acid. The other two inhibitors were separated by methylation with diazomethane, fractional distillation, and column chromatography. The second inhibitor is the a-pyrone 1 . Reaction with diazomethane transforms it into the bi-cyclic compound 19. This bicyclic compound is even more active than the parent a-pyrone 1 . Since we sought structural requirements for bioactivity here also,we tested several synthetic a-pyrones ( 0 - 22) for bioactivity. These compounds had no inhibitory activity. We alio tested the cyclopropane derivatives 23 and 24 In Table II, the bioactivity of the bicyclic compound T9 and two such derivatives is compared. The presence of several carboxylic acid groups seems to be essential (or at least helpful) for bioactivity in this case also. 

The level of the raffinose family of oligosaccharides has been shown to decrease during the germination of seeds of various species (see also, Ref. 12), notably, barley,618 broad bean,22 coffee,630 com,631 cotton,20,8318 lupin,632 pea,833,834 Pinus sp.,635,638 rice,637 runner bean,822 soy-... 

Tests on the germination of seeds in the presence of increasing metal concentrations do not appear to differentiate between tolerant and non-tolerant populations (Verkleij, 1993). 

Fig. 4.—Disappearance of Galactomannan from the Endosperm, and Appearance of Starch in the Cotyledon, During Germination of Seeds olTriganella foenum-graecum that had Already Been Soaked for 24 Hours at 24-26°. (Adapted from Figs. 5 and 6 of Ref. 199.)...

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