Dry-stored Seeds Research Articles

Primary dormancy and annual dormancy cycles in seeds of six temperate wetland sedges

The effects of dry after-ripening and burial in the soil on seed germination of six temperate wetland Carex spp. were investigated. Freshly matured seeds, seeds stored dry for 4 or 8 weeks, and seeds buried at 7-cm depth in a small woodlot, and exhumed at approximately bimonthly intervals over a 2-year period, were tested under a fluctuating (22°/10°C) and a constant temperature regime (15°C) in light and darkness, respectively. Fresh and dry-stored seeds of all species were conditionally dormant at 22°/10° in the light, dormant at 15° in light and darkness and at 22°/10°C in darkness. Dry after-ripening increased significantly germination percentages in three species. Buried seeds of all six species exhibited annual dormancy cycles at 22°/10°C in darkness and 15°C in the light, whereas, no germination occurred at 15°C in darkness. Seeds came out of dormancy in late autumn or winter and entered dormancy in late spring or early summer. Germinability did not show any cyclicity at 22°/10°C in the light in four species and showed weak cyclicity in two species. Seed mortality was low, and no germination occurred during burial. This implies that the six species can accumulate a persistent seed bank.

Evidence that Heavy Grazing May Promote the Germination of Lolium multiflorum Seeds via Phytochrome-Mediated Perception of High Red/Far-Red Ratios

1. Field and laboratory experiments were conducted to test the hypothesis that heavy grazing promotes Lolium multiflorum seed germination at least partially via phytochrome perception of red (R)/far-red (FR) ratios. 2. The crucial experiments were conducted with «field seeds», in contrast to most of the previous work in this area which used only dry-stored seeds. 3. Germination was promoted by severe canopy defoliation even in the absence of animal treading, by preventing canopy-filtered light from reaching seeds exposed to a R light pulse and subsequently placed at the bottom of a natural sward and (in laboratory experiments) by R light pulses perceived by phytochrome

Effects of light and temperature on germination of heteromorphic achenes of Bidens odorata (Asteraceae)

Bidens odorata Cav. (Asteraceae) is an annual weed with heteromorphic achenes that differ in size, weight, and shape within each capitulum. To investigate if the variability of the achene size was correlated with differences in the germination response, achenes were classified in three categories based on size (4, 5–6, and 7 mm), and laboratory experiments were conducted with freshly harvested and dry-stored seeds under several light and temperature conditions. For all conditions tested with fresh seeds, 7-mm achenes germinated faster and with a higher final germination percentage than 4-mm achenes. Germination was inhibited by darkness and far-red light conditions. Experiments conducted with different times of exposure to white light (1 min, 10 min, and 12 h) showed that 4-mm achenes required longer time of exposure to light to maximize their percent germination. However, 7-mm achenes reached similar total percent germination without regard to the period of illumination. Dry storage increased the percent germination significantly in the shorter achenes and altered the light requirement for germination differentially among the morphs. The results suggest a physiological basis of achene heteromorphism that might be related to colonization of different microenvironments. Key words: Bidens odorata, germination, heteromorphism, light, temperature.

Dormancy patterns in buried seeds of Datura ferox and D. stramonium

Seasonal changes in seed dormancy of Datura ferox L. and D. stramonium L. were studied during 2 years in seeds buried in the field and compared with changes in dormancy of dry-stored seeds. Dormancy levels were evaluated by measuring the germination of exhumed and dry-stored seeds under 32:27 °C (nondormant seeds) or 32:12 °C (relatively dormant seeds). Levels of relative or full dormancy did not change during 2 years of dry storage in either species. Seed burial at 20 cm accelerated after-ripening, and primary dormancy disappeared earlier than at 5 cm. However, burial depths greater than 10 cm prevented germination in situ. This inhibition was not due to smaller daily fluctuations of soil temperature with increasing depth, since seeds buried at 20 cm and kept at 32:12 °C also failed to germinate. Transferring seeds to shallower soil layers allowed their germination. Cyclic seasonal changes in dormancy were found in buried seeds of D. ferox but not in D. stramonium. In D. ferox, dormancy was alleviated during the winter and germinability was maximal in early spring; the increase in dormancy was preceded by high late spring – summer temperatures. In D. stramonium most seeds near the soil surface germinated in the field in a brief flush in early winter, at temperatures under which D. ferox did not germinate. Key words: Datura, germination, dormancy, buried seeds, temperature.

Influência de processos de escarificação na germinação e crescimento inicial de Leucaena leucocephala (Lam.) De Wit

Leucaena leucocephala is a species with high economical value and has been subjected to numerous kinds of investigations. This work was designed to develop methods for breaking seed dormancy and induce healthy seedling growth. Dry stored seeds of 1985 crop and fresh seeds of 1986 crop were used. Four treatments of two hundred seeds each were carried out: mechanical scarification; immersion in hot water for 10 minutes; immersion in concentrated sulfuric acid for 10 minutes and untreated. Seeds were incubated in Gerbox boxes, with 20 seeds per box, on filter paper which was moistened with distilled water. The boxes were maintained at a constant temperature of 25 ± 2C and at a photoperiod of 10 hours light and 14 hours darkness. The results indicated that all seed treatments were effective in breaking seed dormancy. The sulfuric acid treatment resulted in the best early seedling growth for the dry stored seeds, while the hot water immersion led to the best growth for the fresh seeds. Significant differences (by t-test, simple and interaction ANOVA, SNK) were obtained among treatments for both seed germination and early seedling growth.

ポリエチレングリコールによる野菜種子の発芽促進 (第1報)

Effects of invigoration with polyethylene glycol 6000 (PEG) on the germination of seeds of eggplant, Cryptotaenia japonica and carrot were investigated. Each seeds were invigorated on blotting paper moistened with PEG solution of -7.5, -10.0, -11.8 and -17.7 bars. Treatment temperatures were 15°, 20° and 25°C. Treatment periods were 7 days and 14 days.1. Germination of seeds of eggplant, Cryptotaenia japonica and carrot were all accelerated by PEG invigoration. Especially, germination of eggplant seeds was much improved at low temperature of 15°C in both germination percentage and germination speed.2. Treatment temperature of 25°C was most effective for eggplant seeds among three temperatures tested. For Cryptotaenia japonica and carrot seeds, no difference was shown among three treatment temperatures.3. Fourteen day treatment period was more effective than 7 day period in eggplant and Cryptotaenia japonica seeds. In carrot seeds, it was oobserved only small difference between 7 day and 14 day treatment periods.4. Addition of 50ppm or 100ppm of gibberellin to the PEG solution much increased the effectiveness of invigoration in eggplant seeds.5. Dry stored seeds after invigoration showed no decrease of effectiveness after 7 days or 14 days of storage in eggplant and Cryptotaenia japonica when germinated on blotting paper. In carrot seeds, a little decrease was found in effectiveness after dry storage.6. In eggplant seeds, effect of invigoration was shown a little smaller in the sand test than in the blotting paper test, especially after dry storage, though effect of invigoration was significant.7. In eggplant, there was found as same the difference of growing days yet at the stage of four leaves as at the germination stage.

GERMINATION, SEEDLING EMERGENCE AND ESTABLISHMENT OF SOME PLANTAGO SPECIES UNDER LABORATORY AND FIELD CONDITIONS*

SUMMARY (a) The germination of Plantago lanceolata L., P. coronopus L., P. major L. ssp.major, P. major L. ssp. pleiosperma Pilger, P. media L., and P. maritima L. in relation to the age of dry-stored seeds was investigated under laboratory conditions. In general, higher percentages of radicle emergence were found with two- to five-year-old seed than with fresh seed. Only P. lanceolata and P. media seeds germinated in complete darkness. A feature of interest was the high germination of both subspecies of P. major in so-called green safelight. (b) The germination and early establishment were tested on various microsites, obtained with glass beads of various sizes. At increasing particle size, an increase in radicle emergence was found for large seeds (P. lanceolata and P. media). Root penetration of the surface occurred sooner on substrates of large particles than on those of small ones. The effects of size of the glass beads on germination and penetration were less in species with small seeds than in species with large seeds. (c) Sowing tests in the field resulted in relatively high numbers of established P. lanceolata and P. coronopus seedlings in open and dry habitats. P. lanceolata seedlings were able to establish themselves in tall dense vegetation layers. P. major ssp. major occurred most frequently on moist and open sites with a compact soil. On trodden paths P. major and P. coronopus seedlings showed opposite mortality curves.

Seed Germination of Hieracium pratense, a Successional Perennial

Hieracium pratense (hawkweed) becomes established from seeds the second spring after disturbance during old-field succession. Hawkweed is a perennial, and its seeds mature and are dispersed in June. Germination of buried and dry-stored seeds of hawkweed was investigated over a 1-yr period. Freshly harvested seeds showed some innate dormancy which was broken by a short period of afterripening Germination of dry-stored seeds in light remained high throughout the testing period except at low temperatures (5-15 C). Germination of seeds buried at 2, 5, and 15 cm was similar to that of the dry-stored seeds, but germination at low temperatures in light increased during the winter months. Laboratory stratification also resulted in increased germination at low temperatures. Germination of dry-stored and buried seed in the light was greater than in the dark The burial experiments indicated short-term viability of hawkweed seeds in the soil. High-temperature drying had no harmful effect on germination, but solutions...

Seed Aging: Chromosome Stability and Extended Viability of Seeds Stored Fully Imbided

Increase in moisture content of seeds of Lactuca sativa L. and Fraxinus americana L. in air-dry storage caused a rapid decline in longevity and an increase in the rate of accumulation of chromosome aberrations. Storage of seeds fully imbibed but unable to germinate allowed a high germination capacity to be maintained for long periods, together with a very low incidence of chromosome aberrations. Seedlings grown from dry-stored seeds showed an increase in morphological abnormalities with length of storage, whereas seedlings from imbibed-stored seeds appeared normal. It is suggested that in dry tissues, enzyme-controlled turnover and repair may be temporarily suspended, and that this may be an important factor in the loss of seed viability in storage. The effect of increasing seed longevity by lowering the moisture content of dry-stored seeds is discussed in relation to this hypothesis. The relevance of the proposal is also discussed in relation to ecological studies.

Delayed Germination and Catalase Activity in Xanthium

1. The upper seeds of Xanthium show constantly less catalase activity per unit of dry substance than the lower seeds. 2. Catalase activity is relatively stable in dry stored seeds, for several months. 3. Stored in imbibed condition in germinators below the temperature for germination, the catalase activity of both uppers and lowers increases immediately following exposure in the germinators. 4. In the field during the germination season, lower seeds increase in catalase activity, while the uppers lag behind them, showing practically no increase. 5. In the laboratory, soaking seeds on ice seems to depress activity slightly, but during subsequent germination, catalase activity increases pari passu with the germination. Upper seeds show much less increase than lowers, except when they actually germinate. 6. Long delay of germination while in the germinators leads first to increased catalase activity of uppers, followed by a decline, which at the end of several months leaves the seeds with no more activity than air dry seeds. The decreased catalase activity accompanies a decreased vigor of germination. 7. The catalase differences in Xanthium seeds are in harmony with other physiological differences, which cooperate to bring about delayed germination of upper seeds with intact coats.