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Seedlings of dicotyledons show a great diversity of form and function. At least five seedling types based on position, exposition and texture of cotyledons and 3 cotyledon types based on function are known. Understanding the relationship between the morphology and function of seedlings can provide an insight into the regenerative strategies of species indifferent vegetation types and assist in constructing appropriate models for biodiversity management. [ABSTRACT FROM AUTHOR]

The article focuses on Calotropis Procera as a subject in food chain studies. It says that this plant is ideal in such inquiries because it is commonly found in waste lands in India and is a good resource provider to various organisms. A photograph illustrating an example of a food chain linked to Calotropis Procera is presented which shows a honeybee on the plant's flower in the hold of a female spider.

• Background and Aims The envelope surrounding the embryo in cucurbit seed, which consists of a single layer of live endosperm cells covered by lipid- and callose-rich layers, is reported to show semi-permeability and also to act as the primary barrier to radicle emergence. Structure, development and permeability of the envelope and activity of cell wall hydrolases during germination of cucumber and muskmelon seeds were investigated.• Methods Sections of seeds were stained with aniline blue and Sudan III. Proton diffusion and endo-β-mannanase activity were detected by tissue printing. A gel-diffusion assay was performed to quantify endo-β-mannanase activity, while the activity of β-glucanase was determined with laminarin as the substrate and glucose formation measured using the GOD-POD method.• Key Results The lipid layer differentiated during seed development in cucumber in the epidermis of a multilayered nucellus, whereas the callose layer appeared to develop outside the endosperm cell layer. Accordingly, the envelope has been called the perisperm-endosperm (PE) envelope. Chloroform treatment of seeds, which resulted in a substantial reduction in Sudan staining of the lipid layer, also enhanced the permeability of the PE envelope to 2,3,5-triphenyltetrazolium chloride. Proton diffusion occurred when the PE envelopes from seeds had their inner surface in contact with bromocresol purple-containing agarose gels, but not when their outer surface was in contact. Substantial endo-β-mannanase activity was present in the caps of the PE envelopes, whereas a marked increase in β-glucanase activity was observed in radicles prior to germination.• Conclusions The lipid layer seems to contribute to the semi-permeability of the PE envelope. The diffusion of protons might create an acidic environment conducive to the activity of cell wall hydrolases, namely endo-β-mannanase (EC 3.2.1.78) and β-glucanase [β(1→3)glucanohydrolase; EC 3.2.1.6], which, in turn, may play a role in the weakening of the PE envelope necessary for the protrusion of the radicle in cucumber and muskmelon seeds. [ABSTRACT FROM AUTHOR]

Seeds of Ocimum americanum L. display an absolute light requirement for germination. The minimal length of the daily photoperiod required to induce a high germination decreased with increasing seed age, but the length of the photoperiod under potential control of terminal far-red light inhibition remained unchanged. There was a gradual escape from the far-red inhibition with increase in the length of the photoperiod. Seeds developed flash photosensitivity after the first 13 h photoperiod. Scarification treatment did not allow the seeds to bypass the light requirement, but it enhanced the germination considerably. Under conditions of natural day length in the field, weakening of the testa by sand may abolish the need for a second exposure to light for most of the seed population, thus rendering them non-photoperiodic. [ABSTRACT FROM AUTHOR]

Seeds of Caesulia axillaris Roxb. displayed an absolute light requirement for germination throughout the period of dry storage at 28°C. The seeds were found to show a gradual increase in percent germination with storage time - reaching a maximum value between 8-14 months and then a sharp decline. Percent water uptake and photosensitivity were at maximum after a 5-day imbibition period in the dark in both seedlots studied. Seedlot I, which was only marginally responsive to far-red light, showed a nearly complete red-far-red reversal effect in contrast to seedlot II. The latter also displayed a considerable promotion of germination in far-red light. Interestingly, a noticeable degree of heterogeneity, besides the one observed in both seedlots with reference to red light, was found to exist in seedlot II for far-red light. Exogenous application of nitrate and .ammonium, at the levels occurring in soil during seed germination/seedling emergence phase of the plant in nature, promoted a considerable proportion of high Ø-requiring seeds. to geminate under irradiation conditions establishing low Ø-value. The probable ecological implication of this response has been discussed.. Little correlation was found: between the requirement for an exogenous supply of nitrate and the endogenous nitrate level in the seeds in their response to far-red light. [ABSTRACT FROM AUTHOR]

Seed germination in Hygrophila auriculata (Schumach.) Haines was found to be under phytochrome control. Exogenous indole-3-acetic acid (IAA) application at concentrations greater than 1×10 M inhibited germination in the dark, as well as in the light. Red light-induced radicle growth, prior to radicle protrusion through seed coverings and measured as an angle formed by the radicle with the seed axis, was found to be inhibited by IAA. Delay in application of IAA to red light-irradiated seeds resulted in a gradual increase in percent germination, which probably corresponded to the time-course of Pfr action. It is suggested that exogenously applied IAA probably reimposes dormancy in red light-induced seeds of Hygrophila auriculata. [ABSTRACT FROM AUTHOR]