Dormant seeds

On a no-dig plot, weeds are drastically reduced as dormant seeds are not brought to the surface by the soil s being turned over. A mulch further reduces weed numbers, but is not essential. Light hoeing is effective on bare soil and gradually depletes the reserve of weed seeds. Loosen any perennial weeds with a fork and lift them out, disturbing the soil as little as possible. 

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. 

In addition to the reproduction of desirable species, dormant seed of pin cherry (Prunus pensylvanlca) are typically stored in the litter of Northern hardwood stands and germinate after cutting or disturbance. Storage of pin cherry seed in the litter for periods in excess of 50 years is well known (11, 12). Many of these stored pin cherry seeds germinated on fencedTweeded plots. At the peak,... 

The soil contains millions of seeds per hectare in the seed bank and these individuals are easily overlooked as members of the plant community. The dormant seeds can survive for decades in the soil hence, a population of annual plants does not have to be successful at reproducing every year in order to be sustainable. In contrast, a specialist insect herbivore of that annual species can rarely be sustained in a locaUty without a reUable source of food annually. 

Apparendy all forms of life, both plant and animal, with the possible exception of simple forms, such as bacteria that have not been studied dioroughly. either synthesize the vitamin from other nutrients or require it as a nutrient Dormant seeds contain no measurable quantity of the vitamin, but after a few hours of soaking in water, die vitamin is formed. 

Harada, W.S., The effects of Ethephon on dormant seeds of cultivated sunflower (Helianthus annum L.), in Proceedings of the 10th International Sunflower Conference, Toowoomba, Australia, 1982, pp. 1-8. 

There are two important classes of allelochemicals synthesized by oxidative cleavages of tetraterpene carotenoids. One is the plant hormone abscisic acid (ABA, 31) that plays important roles in growth and development of plants, especially in seed development and dormancy.17 Dry dormant seeds contain relatively large amounts of ABA, particularly in the seed coats. ABA and phenolic allelochemicals in the seed coats are easily released into the environment when the seeds are imbibed, resulting in inhibition of seed germination and seedling growth of plants in the vicinity. Both ABA and the phenolic compounds are rapidly broken down in the soil, and therefore the inhibition is short-lived. 

Fourth paper towel was placed on top of them. Paper towel were rolled gently to form a tube. Rolled papers were placed in suitable container in upright position covered with polyethylene bags and kept in germinating chamber on recommended temperature 20-25°C (Jennifer and James, 1997). Germination was not observed in any of the species. These dormant seeds were subjected to different dormancy breaking treatments. 

Frankland B, Wareing PF (1962) Changes in endogenous gibberellins in relation to chilling of dormant seeds. Nature 194 313-314... 

Many seeds placed in distilled water in Petri dishes under optimum conditions for germination show a triphasic pattern of water uptake as shown in Figure 4.6. Initial uptake of water in Phase I (i.e. imbibition) is a consequence of the matric forces (i/cell walls and cell contents of the seed, and this uptake occurs irrespective of whether a seed is dormant or non-dormant, viable or non-viable. Phase II is the lag period of water uptake, when the matric potential is high (less negative), as is the solute or osmotic potential Dead and dormant seeds maintain this level of hydration typical of Phase II, but unlike germinating seeds they do not enter Phase III, which is associated with visible germination. 

Ellis, R.H., Hong, T.D., Roberts, E.H., 1983. A note on the development of a practical procednre for promoting the germination of dormant seed of grape (Vitis spp.). Vitis 22, 211-219. 

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