Dicotyledon seed

A good example of a dicotyledon seed is the field bean. If its pod is opened when nearly ripe it will be seen that each seed is attached to the inside of the pod by a short... 

Especially in dicotyledonous plant species such as tomato, chickpea, and white lupin (82,111), with a high cation/anion uptake ratio, PEPC-mediated biosynthesis of carboxylates may also be linked to excessive net uptake of cations due to inhibition of uptake and assimilation of nitrate under P-deficient conditions (Fig. 5) (17,111,115). Excess uptake of cations is balanced by enhanced net re-lea,se of protons (82,111,116), provided by increased bio.synthesis of organic acids via PEPC as a constituent of the intracellular pH-stat mechanism (117). In these plants, P deficiency-mediated proton extrusion leads to rhizosphere acidification, which can contribute to the. solubilization of acid soluble Ca phosphates in calcareous soils (Fig. 5) (34,118,119). In some species (e.g., chickpea, white lupin, oil-seed rape, buckwheat), the enhanced net release of protons is associated with increased exudation of carboxylates, whereas in tomato, carboxylate exudation was negligible despite intense proton extrusion (82,120). 

The mature fruit consists of a pod usually 6 tolO in. long containing 20 to 40 seeds or beans covered by a white, mucilaginous pulp. The beans are dicotyledonous, oval-shaped, and about 1 to 1 1/2 in. long with colors varying from white to shades of purple. 

I The distinction between mono-and dicotyledonous plants is quite simple monocotyledons are flowering plants which have only one seed leaf, and usually have parallel-veined leaves, flower parts in multiples of three, and no secondary growth in stems and roots, whereas dicotyledons are flowering plants with two seed leaves (cotyledons), net-veined leaves, flower parts in fours and fives, and in woody plants have cambium, a layer of formative cells between the wood and the bark the cells increase by division and differentiate to form new wood and bark. 

The seeds of dicotyledonous plants have two cotyledons, or seed leaves, which are part of the embryo. The cotyledons usually are the main storage tissue, although in some plants (such as castor bean) the endosperm also has a storage function. During development in the field, seeds gradually accumulate storage oils, proteins and carbohydrates (Table 3.1). In the seed, the cotyledon structure is relatively simple. The remainder of the embryo, the embryonic axis, consists mostly of undifferentiated cells, but provascular tissue can be detected that develops into vascular tissue in the seedling. 

In the quest to find other plants that are suitable as bioreactors, various monocoty-ledonous and dicotyledonous species have been tested. These include corn [16], rice and wheat [17], alfalfa [18], potato [19, 20], oilseed rape [21], pea [22], tomato [23] and soybean [24]. The major advantage of cereal crops is that recombinant proteins can be directed to accumulate in seeds, which are evolutionar specialized for storage and thus protect proteins from proteolytic degradation. Recombinant proteins are reported to remain stable in seeds for up to five months at room temperature [17] and for at least three years at refrigerator temperature without significant loss of activity [25]. In addition, the seed proteome is less complex than the leaf proteome, which makes purification quicker and more economical [26]. 

Potato type II (Potll) inhibitors are disulfide-rich peptides of approximately 50 amino acids in size. They were first discovered in leaves, seeds, and other organs of Solanaceae and are a source of much interest as plant defense proteins. Recently, Barta et analyzed expressed sequence tag (EST) and genomic data and discovered 11 genes that code for Potll inhibitors in various monocotyledonous and dicotyledonous plants. Potll inhibitors are expressed as large precursor proteins that contain up to eight sequence repeats of the inhibitor precursor. In one particularly fascinating case from the ornamental tobacco (N. data), the precursor adopts a circular permuted structure.Barta et al. observed that genes outside the Solanaceae family seem... 

Steiner U et al., Molecular characterization of a seed transmitted clavicipitaceous fungus occurring on dicotyledoneous plants (Convolvulaceae), Planta 224 533— 544, 2006. 

The biosynthesis pathway of GAs in plants has long been studied since their discovery as endogenous growth regulators. There have been two key approaches to unravel the biosynthetic routes and identify the genes encoding the biosynthetic enzymes. First, a cell-free system prepared from immature seeds of dicotyledonous species such as Marah macrocarpus and Cucurbita maxima allowed researchers to purify and characterize the GA... 

Steiner, U., Ahimsa-Muller, M. A., Markert, A., Kucht, S., Gross, ]., Kauf, N., Kuzma, M., Zych, M., Lamshoft, M., Furmanowa, M., Knoop, V., Drewke, C. and Leistner, E. (2006) Molecular characterization of a seed transmitted clavicipitaceous fungus occurring on dicotyledoneous plants (Gonvolvulaceae). Planta, 224, 533-44. 

Steiner U, Ahimsa-Muller MA, Markert A, Kucht S, Gross J, Kauf N, Kuzma M, Zych M, Lamshoft M, Fttrmanowa M, Knoop V, Drewke C, Leistner E. Molecular characterization of a seed transmitted clavicipitaceous fungus occitrring on dicotyledoneous plants (Convolvulaceae). Planta. 2006 224 533-544. 

Pig. 172.—Morphology of a typical dicotyledonous plant. A, leaf, pinnately-netted veined B, portion of stem, showing concentric layers of wood C. ground-plan of flower (the parts in 5 s) D, perspective of flower E, longitudinal section of seed, showing dicotyledonous embryo. Gager,)... 

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