Role In Germination Research Articles

Germination Response in a Large-Seeded Neotropical Tree Species, Gustavia superba (Lecythidaceae)

This six-month study examined percent germination, days until germination, and early seedling survival of Gustavia superba (Lecythidaceae) through field experiments in a tropical moist forest in Panama. The study had three goals: (1) to examine whether germination is a factor determining density of seedlings at three forest sites with different ages; (2) to test whether burial of seeds affects germination; and (3) to test if microsite conditions associated with light gap, gap-edge, or forest understory influence germination. The experiment, which was designed to fit a three-way ANOVA model, used three study sites, three microsites, two burial treatments, four replicates and 25 seeds in each replicate (1800 seeds total). Although seedling densities of G. superba at the forest sites varied inversely with age of forest, there was no evidence that germination success contributes to this pattern. Results indicated that this species germinates readily under most conditions: the overall mean was 85.4 percent and only six of 72 plots had less than 70 percent germination. Germination percent was reduced and mean number of days until germination was increased in the largest light gap. However, percent germination and days until germination did not differ among sites when only seeds in the understory microsite were compared. Burial of seeds and microsite conditions had minor effects on germination. Seedling mortality occurring soon after germination was not large (5.7%). It is concluded that G. superba is not a tropical species whose seeds germinate in response to a light gap but its seeds do germinate successfully under a range of microsite conditions. ALTHOUGH PLANT POPULATION SIZES can be affected by mortality at many stages, the seed to seedling transition generally is considered to be one of the most vulnerable. Mortality agents include pathogens, insect and vertebrate predators of seeds, as well as abiotic factors affecting germination levels. All these factors are intertwined in affecting seedling establishment. As a result, controlled experiments are required to identify the separate contribution of each factor. The focus of this paper will be to discuss the role of germination per se in seedling establishment of Gustavia superba (Kunth) Berg (Lecythidaceae), a

Mobilisation of storage reserves during fern spore germination

SynopsisWe have studied morphological and biochemical aspects of storage reserves and their degradation in fern spores during the germination process. The results presented here are concerned with the fate of lipid, protein and phytic acid. Depletion of lipid reserves and breakdown of lipid bodies was directly correlated with increased activity of glyoxylate cycle enzymes during early stages of germination. Degradation of protein reserves coincided with the depletion of salt soluble proteins (globulins) from the spores and was related to the time when high activity of aminopeptidase and carboxypeptidase was observed. Lipid and protein appeared to play an important role in germination. Phytic acid reserves were present in the spore and were hydrolysed by phytase after germination occurred. This storage material was implicated in growth of the prothallus.

Interaction between a Bacillus cereus spore hexosaminidase and specific germinants.

A purified coat-associated hexosaminidase from spores of Bacillus cereus was studied to determine whether it could promote germination of dormant spores. Spores of a coat-deficient mutant as well as chemically extracted spores were used as substrate. Both of these spore preparations responded poorly to most germinants. However, absorbance loss was accelerated when the hexosaminidase was added in the presence of L-alanine. Enzyme alone was not effective. The addition of D-alanine inhibited completely the absorbance loss caused by hexosaminidase and L-alanine. Calcium dipicolinate and L-alpha-aminobutyric acid activated the hexosaminidase to some extent, but these chemicals were much less effective than L-alanine. In addition to the absorbance loss, the spores treated with enzyme and germinants released hexosamine and lost heat resistance and phase whiteness. The results suggest that this particular enzyme might have a role in germination.

<i>In vitro</i> propagation of pointed gourd (<i>Trichosanthes dioica</i> Roxb.) through encapsulated shoot tips

Plants were regenerated from encapsulated shoot tips of pointed gourd. Shoot tips isolated from multiple shoot cultures of AM-8 and AM-15 cultivars of pointed gourd were encapsulated in sodium alginate beads. For germination and shoot proliferation, encapsulated shoot tips (artificial seed) were cultured in MS basal medium containing different concentrations and combinations of BAP and NAA. Use of MS medium resulted in 90% conversion of encapsulated shoot tips into plantlets. The results exhibited that BAP and combinations of BAP and NAA play an important role in germination of artificial seed being encapsulated by sodium alginate beads. The plantlets were successfully established in earthen pot. Under the present study, limited experimental efforts have been made to establish the protocol for encapsulating the shoot tips for the production of artificial seed and their subsequent regeneration. It is the first report in Bangladesh in developing artificial seed production technique using vegetative tissue of pointed gourd. Key Words: In vitro propagation; pointed gourd; shoot tips. DOI: 10.3329/bjar.v34i4.5832Bangladesh J. Agril. Res. 34(4) : 555-563, December 2009

Abscisic Acid Levels and Seed Dormancy

Dormant seeds from Fraxinus species require cold-temperature after-ripening prior to germination. Earlier, we found that abscisic acid (ABA) will inhibit germination of excised nondormant embryos and that this can be reversed with a combination of gibberellic acid and kinetin. Using Milborrow's quantitative "racemate dilution" method the ABA concentration in 3 types of Fraxinus seed and pericarp were determined. While ABA was present in all tissues, the highest concentration was found in the seed and pericarp of dormant F. americana. During the chilling treatment of F. americana the ABA levels decreased 37% in the pericarp and 68% in the seed. The ABA concentration of the seed of the nondormant species, F. ornus, is as low as that found in F. americana seeds after cold treatment. Experiments with exogenously added ABA solutions indicate that it is unlikely that the ABA in the pericarp functions in the regulation of seed dormancy. However, the ABA in the seed does seem to have a regulatory role in germination.

The β-glucosidase and β-galactosidase components of Medicago sativa L.

The β-galactosidase (EC.3.2.1.23) of alfalfa seed is not readily separated from the β-glucosidase (EC.3.2.1.21) activity. Heat denaturation studies and reactions to specific inhibitors indicate the separate identity of the two enzymes. The β-glucosidase may be fractionated into several active components. A role in germination is suggested.