J.A Magembe, 'Effect of physical scarification and Gibberellic acid treatments in germination Trichilia emetica seed', vol. 5, pp.163-177, 1988 | Seeds of Trichilia emetica were subjected to 3 types of physical seed coat scarification, i.e. unscarified, partial removal of seed coat at radicle end, and complete removal of seed coat. These treatments were combined in a factorial arrangement with gibberellic acid at 5 concentrations: 0, 250, 500, 750 and 1,000 ppm, and replicated 4 times. Unscarified seeds without and with gibberellic acid attained cumulative germination of up to 40%. Partial and complete removal of seed coat resulted in over 90% germination. Application of gibberellic acid to both unscarified and scarified seeds produced marginal but significant effects on cumulative germination, germination value and germination energy. Application of gibberellic acid to seeds whose seed coat had been completely removed resulted in complete emergence of all seeds sown. Observations indicate that the poor germination associated with T. emetica seeds is due mainly to the impermeability of the seed coat and aril to fluids (water and gases). It is recommended that the seed coat of T. emetica seeds be partly or completely removed before sowing

The embryo length, moisture content and some other physical features of the nuts of both Cola acuminata (P. Beauv) Schott and Endlicher and Cola nitida (Vent.) Schott and Endlicher were examined. Fresh and dry weights, nut length and width, embryo and embryo-groove lengths increased with nut size in both species. Nut moisture content decrease with increase in nut size in both species, especially in C. acuminata than in C. nitida. Embryo length relative to nut width was much higher in C. acuminata than in C. nitida. Correlations between these morpho-physical factors and rates of germination in both species showed that germination response in C. nitida was mainly determined by nut size-related factors such as class midpoints, nut fresh and dry weights and nut length and width. Embryo length and embryo-groove length were critical for germination of both species but they were much more so for germination of C. nitida than of C. acuminata. Germination in C. acuminata was negatively correlated with nut moisture content compared with C. nitida where there was no significant relationship. On nut cotyledon basis, both cotyledon number and embryo length positively influenced germination in C. acuminata. These relationships showed that embryo and embryo-groove lengths, nut moisture content and nut cotyledon number are both jointly and severally responsible for the differential rates of germination in the two kola species.

Germination of a perennial alyceclover [Alysicarpus vaginalis (L.) DC.] accession, which has potential value as a grazing-tolerant pasture legume for peninsular Florida and some tropical locations, was evaluated for response to seed storage and scarification treatments. Both practical means of enhancing germination and characteristics of germination limitations were considered. A series of experiments evaluated responses to storage time, storage temperature, physical seed coat disruption with sandpaper, and exposure to steam, hot water, and dry heat. Freshly harvested seed failed to germinate regardless of seed treatment. Seed that had been stored for 3 to 8 yr produced rapid, essentially complete germination when scarified with sandpaper. A storage period of approximately 16 wk was sufficient for rapid germination regardless of storage temperature. At 4 wk of storage, a storage temperature of 7°C resulted in higher germination than storage at 24°C. Steam exposure times of from 40 min to 2 h or exposure to 80°C water for 5 to 10 min produced slow germination rates but greater than 60% germination after 56 d. Exposure to dry heat for 6 or 12 h produced poorer results (48% germination at 56 d) than steam or hot water. These heat treatments could have value either where mechanical scarification is not available or in situations where sporadic, early season rainfall creates high pasture establishment risks for seed lots that have been scarified to provide rapid, complete germination. Failure of scarified, imbibed, fresh seed to germinate indicates a physiological limitation to germination. Rapid, essentially complete germination of these seed lots after storage periods of from 16 wk to a number of years indicates that an afterripening period overcomes this limitation. Physical seed coat impermeability or hardseededness is demonstrated by the need for scarification even in seed that has been stored long enough to meet the after-ripening requirement. Contribution of the Florida Agric. Exp. Stn., Journal Series no. 8276.

The influence of temperature and various scarification treatments on the physical changes of the lemma and germination of bahiagrass (Paspalum notatum Flugge) were studied. Mechanically scarified seeds readily germinated on an agar medium. Acid-scarified seeds germinated better than untreated seeds, but not as readily as mechanically scarified seeds. All caryopses excised from nongerminated acid-scarified seeds readily germinated on an agar medium after 17 days. Excised caryopses were placed on a temperature gradient bar corresponding to positions at 15.5 degrees, 21 degrees, 26.5 degrees, 32 degrees, and 37.5 degrees C. All caryopses germinated at 21 degrees to 37.5 degrees, but germination and seedling growth were best at 32 degrees to 37.5 degrees. Lipase and acid scarification improved germination when seeds were held at 24 degrees, but did not enhance germination when seeds were held at 32 degrees. Scanning electron microscopy revealed that acid scarification removed the cuticular substances of the lemma and the substances in the fissure of the germinating lid, probably facilitating entrance of the water and earlier emergence of the coleorhiza. The data suggest that the lemma and palea are physical barriers in bahiagrass.

Our results concerning in vitro culture study showed a linear relationship between germination percentages and temperature degrees tested. Since seeds germinated under 30 C gave a percentage about 10 times that recorded with 10 C. An apposite relationship was noticed between number of days until the beginning of seed germination and temperature degrees. The least number of days was with 30 C, whereas the greatest interval was with 10 C. On the other hand, insignificant differences between treatments exposed to light or to dark were detected.

The Sahellan zone Is characterized by harsh conditions for crop growth: chemically and physically poor soils, low and uncertain rainfall, and high temperatures. Crops are particularly sensitive to the physical environment during the germination and seedling stages of crop establishment. Appropriate soli management techniques reduce the risk for crop failure and help to ensure good crop stands.

Diclofop {(±)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid} controls downy brome (Bromus tectorum L.) when mechanically incorporated after application, but preemergence surface applications result in erratic control of downy brome. To determine the physical factors that enhance diclofop bioactivity, laboratory and greenhouse studies were conducted with two soils: sand (Ustic Torripsamment) and sandy clay loam (Aridic Paleustoll). An oat (Avena saliva) root bioassay was used to measure bioactivity of diclofop. Movement of diclofop downward by simulated rainfall was affected by soil type and time of rainfall event. Oat root growth of seed planted 25 mm deep was reduced by >80% in the sand when 25 mm of rain was applied, but less than 30% in the sandy clay loam. Diclofop movement was reduced if the rainfall event was delayed by 4 d after application to the sand soil, indicating the need for precipitation within a few days after diclofop application. Surface straw interception and retention reduced diclofop activity by 20 to 30%, but simulated rainfall reduced this retention. Diclofop bioactivity was greatest when applied before oat seed germination. Diclofop applied to the soil surface after oat seedlings had emerged reduced plant growth 20 to 30%, while diclofop applied before oat germination reduced plant growth 75 to 85%. Preemergence surface applications of diclofop to the sand soil would be suitable for irrigated wheat (Triticum aestivum L.) production on the sand, provided that diclofop was applied before weed germination and an irrigation of 25 mm occurred within 2 to 4 d after application. Contribution from the USDA-ARS, Northern Plains Area.

Bean seeds var. Calima were stored in airtight containers during 32 wk., at 30 degrees Celsius and 7 moisture levels between 10.3 and 14.2 percent (humid basis). Every 2 wk., the physical, physiological, and sanitary quality of the seeds was evaluated by doing individual lot samplings of each moisture level. With the exptl. data on germination, emergence, and vigor, mathematical models with regression coefficients (r(2)) of 0.85, 0.93, and 0.77 resp., were obtained. Bean seeds with high initial quality and a max. MC of 12 percent (humid basis) do not undergo significant loss of their physiological quality when airtight stored for up to 8 mo. at 30 degrees Celsius. (AS-CIAT)

Article concernant l'action in vitro de cinq fongicides et quelques facteurs physico-chimiques sur la germination conidienne et la croissance mycelienne d'Ascochyta rabiei (PASS) LAB., agent de l'anthracnose du pois chiche en Tunisie. L'etude montre que les sucres notamm. le lactose, le glucose et le saccharose favorisent la germination du pathogene et induisent sa croissance. L'acide malique reduit la germination des spores. Les basses temperatures ne sont pas lethales pour le parasite. Les essais des fongicides, montrent que le manebe est tres efficace contre la germination et la croissance du pathogene

The mayor objectives of this study were to determine the effects of nitrogen (N), phosphorous (P), potasium (K) and plant population (PP) on seed yield and quality of three sunflower (Helianthus annuus L.) varieties, as well as to study the relationships between physical and biological seed characteristics. Yield of different seed sizes varied with PP but not with fertilization. Total seed yield showed a positive response to N and PP. The three varieties showed similar responses to N, P, K and PP. Three was no effect of fertilization factor and PP on biological quality of seed of intermediate size, as measured by per cent germination and seeding vigor. Seed size was a determinant factor for seedling vigor measured as postgermination dry weight production.