The study of seed germination of medicinal plant species has received special attention from the scientific community due to the increased demand for these plants in the pharmacological industry, coupled with the need to make rational crops for the
Seed germination of four Litchi chinensis Sonn. cultivars (`Deshi', `Kasba', `Purbi', and `Early Bedana') was studied under various conditions, viz. in soil beds exposed to sunlight or in shade, in sand beds exposed to sunlight or in shade, and on moist filter paper. Among all, shaded, humid sand at 35 ± 2C gave the highest germination. Delaying sowing seeds after removal from the fruit significantly reduced germination. Litchi seeds held in polyethylene bags up to 4 days at 37 ± 2C at 90% relative humidity delayed loss of seed viability. Germination was improved by ethephon in `Deshi' and `Early Bedana', by IBA in `Deshi' and `Purbi', and by 100 mm GA3 in all litchi cultivars. Cultivars responded differently to growth regulators, with `Deshi' responding significantly better than `Purbi', `Kasba', or `Early Bedana'. These studies point to the recalcitrant nature of litchi seeds. Chemical names used: gibberellic acid (GA3); indole butyric acid (IBA); 2-chloroethylphosphonic acid (ethephon).
Sharma, 1987 ). Xia et al. (1990) found that litchi seeds germinated fully when harvested at 10 d before fruit maturity or at fruit ripening time, but entirely lost seed viability after 6 d of natural drying. Ray and Sharma (1987) pointed out that
, 1977 ). There is a considerable variety of methods that can be used for dormancy-breaking and seed germination among different Prunus species ( Ellis et al., 1985 ; Finch-Savage et al., 2002 ; Grisez, 1974 ; Suszka, 1962 ). Cherries generally have
Priming or presoaking seed of common carpetgrass (Axonopus affinis Chase) and centipedegrass [Eremochloa ophiuroides Munro. (Kunz)] increased germination percentage and decreased mean time of germination (MTG) at 20, 25, and 30 °C. The effect of presoaking and priming was dependent on grass species and temperature. The optimum seed germination temperature for both of these warm-season species was 30 °C. Maximum effect on common carpetgrass or centipedegrass seeds was achieved by priming in 2% KNO3; higher concentrations did not improve germination percentage or MTG, and 4% was in some cases detrimental. Germination was higher and MTG lower at 20 and 30 °C than at 15 °C. Presoaking common carpetgrass and centipedegrass seeds was the most efficient seed enhancement treatment for germination at 30 °C.
Factors contributing to genetic differences in low temperature seed germination of tomato (Lycopersicon esculentum Mill.) were examined by comparing the cold germinating (CG) accession PI 341985 the non-cold germinating (NCG) ‘Centennial’ and random F4 lines with varying low temperature germinating abilities. Rate of radicle elongation at 10°C was similar for both parental genotypes indicating that differences in emergence at 10° are not due to growth rates, but rather to more rapid initiation of germination activities in CG. Preincubation of seeds in hypertonic salt solutions enhanced rate of germination at 10°C equally in both lines, but did not substitute for the genetically based cold germinating ability. Low temperature germinating ability is associated with sprouting at high osmotic concentrations, and with a several fold higher rate of increase in peroxidase activity during the first 10 days of incubation at 10°. Germination at 10° of the NCG lines is improved by activated carbon in the germination media whereas no enhancement occurred in CG lines. Inhibition and/or delay in germination at 10° in NCG lines is due, in part, to low temperature induced formation of activated carbon adsorbable inhibitors of seed germination.
High summer temperatures may reduce plant stands of direct-seeded fall broccoli (Brassica oleracea var. italica Plenck). The influence of constant and diurnally alternating temperatures in the range of 5 to 42C on germination and emergence of `Packman' broccoli was evaluated. Germination was defined as protrusion of the radicle from the seedcoat, and emergence as 10 mm elongation of the radicle. The range of constant temperatures from 10 to 30C for 14 days was satisfactory for 90% germination and 75% emergence. However, alternating temperatures extended the acceptable emergence range to 5/17 through 20/32C. Since soil temperatures in warm climates often exceed 20/32C during the summer, high-temperature inhibition of seed germination and seedling emergence is a potentially important factor limiting direct-seeded broccoli stands.
Cold tolerance (CT) of 31 tomato accessions (cultivars, breeding lines, and plant introductions) representing six Lycopersicon L. sp. was evaluated during seed germination and vegetative growth. Seed germination was evaluated under temperature regimes of 11 ± 0.5 °C (cold stress) and 20 ± 0.5 °C (control) in petri plates containing 0.8% agar medium and maintained in darkness. Cold tolerance during seed germination was defined as the inverse of the ratio of germination time under cold stress to germination time under control conditions and referred to as germination tolerance index (TIG). Across accessions, TIG ranged from 0.15 to 0.48 indicating the presence of genotypic variation for CT during germination. Vegetative growth was evaluated in growth chambers with 12 h days/12 h nights of 12/5 °C (cold stress) and 25/18 °C (control) with a 12 h photoperiod of 350 mmol.m-2.s-1 (photosynthetic photon flux). Cold tolerance during vegetative growth was defined as the ratio of shoot dry weight (DW) under cold stress (DWS) to shoot DW under control (DWC) conditions and referred to as vegetative growth tolerance index (TIVG). Across accessions, TIVG ranged from 0.12 to 0.39 indicating the presence of genotypic variation for CT during vegetative growth. Cold tolerance during vegetative growth was independent of plant vigor, as judged by the absence of a significant correlation (r = 0.14, P > 0.05) between TIVG and DWC. Furthermore, CT during vegetative growth was independent of CT during seed germination, as judged by the absence of a significant rank correlation (rR = 0.14, P > 0.05) between TIVG and TIG. A few accessions, however, were identified with CT during both seed germination and vegetative growth. Results indicate that for CT breeding in tomato, each stage of plant development may have to be evaluated and selected for separately.
pretest has been successful in other crops, such as sorghum ( Tiryaki and Andrews, 2001 ), and would allow quicker and more efficient selections to be made. The objectives of this study are to determine how temperature affects spinach seed germination and
-containing compounds ( Bethke et al., 2007 ) are used to overcome seed dormancy and improve seed germination. This investigation explored options to accelerate black cumin seed germination using presowing seed treatments to enhance the uniformity of emergence in field