(a) Write the botanical name, family, morphology of useful parts and uses of the following plants: (i) Safflower (ii)…

(a) Botanical Name, Family, Useful Parts and Uses

(i) Safflower: Carthamus tinctorius, family Asteraceae. The useful parts are the fruits and the florets. The fruit is a white, four-angled, smooth cypsela (achene), commonly called the seed, with a hard hull and an oily kernel (about 30–40% oil). The florets are tubular, orange-red to yellow, borne in a capitulum surrounded by spiny involucral bracts. Uses: the seed oil is rich in linoleic acid (high-oleic types also exist) and is used as a cooking oil and in paints and varnishes; the florets yield the red dye carthamin and a yellow dye, and are used as a food colour and cheap substitute for saffron; the oilcake is cattle feed. India grows it mainly in Maharashtra and Karnataka.

(ii) Fennel: Foeniculum vulgare, family Apiaceae. The useful part is the fruit, a greenish-brown, oblong cremocarp that splits into two mericarps, each with five prominent ridges and oil canals (vittae) between them; it is borne in compound umbels of small yellow flowers. Uses: the fruits (saunf) are a spice and mouth freshener; their volatile oil, rich in anethole, is carminative and used in gripe water, digestive preparations, liqueurs and perfumery; the feathery leaves and the swollen leaf bases of Florence fennel are eaten as a vegetable. Gujarat and Rajasthan are the main producers.

(iii) Chicory: Cichorium intybus, family Asteraceae. The useful parts are the taproot and leaves. The root is a long, fleshy, tapering taproot with a milky latex, storing the fructan inulin instead of starch; the leaves form a basal rosette, and the plant bears blue ligulate florets. Uses: the dried, roasted and ground root is blended with coffee (common in South Indian filter coffee) as a substitute or extender; the root is a commercial source of inulin, a prebiotic dietary fibre; the leaves and etiolated shoots (witloof) are salad vegetables, and forage chicory is fodder.

(iv) Tapioca (cassava): Manihot esculenta, family Euphorbiaceae. The useful part is the tuberous adventitious root: cylindrical to spindle-shaped, with a thin brown outer skin, a pinkish or white cortex (rind) and a white, starchy flesh with a central fibre strand. The roots contain the cyanogenic glucoside linamarin, so they must be peeled, soaked or cooked before eating. Uses: a staple carbohydrate food in Kerala and much of the tropics; starch for sago (sabudana), noodles and papads; industrial starch for textiles, paper, adhesives and ethanol; dried chips as animal feed. Tamil Nadu and Kerala are the main producers.

(v) Teak: Tectona grandis, family Lamiaceae (formerly Verbenaceae). The useful part is the heartwood of this large deciduous tree. The wood is ring-porous to semi-ring-porous, golden brown darkening with age, moderately heavy, straight-grained and oily (containing tectoquinone), with silica in the cells. Uses: it resists termites, fungi and decay and is dimensionally stable, so it is prized for furniture, doors and windows, ship and boat decks, railway carriages, bridges and plywood veneers. Madhya Pradesh, Maharashtra and Kerala (Nilambur) are major teak areas.

(b) Protoplast Culture, Its Limitations and Somatic Hybridization

Steps in protoplast culture:

1. Source tissue: young, fully expanded leaves (mesophyll) or cell suspensions are surface-sterilised; the lower epidermis may be peeled off.
2. Isolation: the tissue is incubated in cellulase, macerozyme (pectinase) and hemicellulase in a medium containing an osmoticum (mannitol or sorbitol) that keeps the naked protoplasts from bursting (the enzymatic method of Cocking, 1960).
3. Purification: the mixture is filtered through a nylon mesh and the protoplasts are separated from debris by low-speed centrifugation and flotation on a sucrose or Percoll gradient.
4. Viability testing: fluorescein diacetate (FDA) staining, cyclosis and exclusion of Evans blue.
5. Culture: protoplasts are plated at an optimum density in liquid, agarose-bead or hanging-drop culture, sometimes with a feeder layer, on a medium such as Kao and Michayluk's or modified MS, with auxin, cytokinin and a gradually reduced osmoticum.
6. Wall regeneration and division: a new cell wall forms within 2–4 days, the cells divide into microcolonies and then callus.
7. Plant regeneration: callus is transferred to a regeneration medium to form shoots and roots (organogenesis) or somatic embryos, and plantlets are hardened. The first plants from protoplasts were obtained in tobacco (Takebe and colleagues, 1971).

Limitations:

1. Many species, especially cereals, grain legumes and woody plants, are recalcitrant and regenerate poorly or not at all.
2. The procedure is technically demanding and costly: enzyme quality, osmotic conditions and plating density must be optimised for each genotype.
3. Somaclonal variation, aneuploidy and loss of regeneration ability in long-term cultures.
4. Low plating efficiency, and survival depends strongly on the donor plant's physiological state.

Role of somatic hybridization in crop improvement: protoplasts of two species are fused with polyethylene glycol (PEG) or by electrofusion, and hybrids are selected using markers such as complementation, fluorescent labels or herbicide and antibiotic resistance.

1. It overcomes sexual incompatibility and combines genomes of species that cannot be crossed, for example transferring late-blight resistance from Solanum bulbocastanum and virus resistance from S. brevidens into potato.
2. It produces cybrids, combining the nucleus of one parent with the cytoplasm of another, to transfer cytoplasmic male sterility; for example, Ogura CMS from radish was transferred to Brassica rapeseed through protoplast fusion, and triazine-resistant chloroplasts were transferred as well.
3. It creates asymmetric hybrids that transfer a few chromosomes or traits from a wild donor.
4. It produces novel amphiploids such as the pomato (potato + tomato; Melchers, 1978) and has been used in Citrus breeding for rootstocks and seedless triploids. Its limits are sterility and genetic instability of many hybrids.

(c) Axial Parenchyma and Ray Parenchyma in Dicot Wood

Types of axial parenchyma, classified by their relation to vessels as seen in transverse section:

Apotracheal (not associated with vessels):

1. Diffuse: single strands scattered among fibres (e.g., Pyrus).
2. Diffuse-in-aggregates: short tangential lines between rays (e.g., Alnus).
3. Banded: tangential bands independent of vessels (e.g., Ficus, Diospyros), including marginal (initial or terminal) bands at the limit of a growth ring (e.g., Magnolia, Juglans, teak).

Paratracheal (associated with vessels):

1. Scanty: a few cells around the vessels, forming an incomplete sheath (e.g., Eucalyptus).
2. Vasicentric: a complete sheath around a vessel (e.g., Dalbergia).
3. Aliform: a sheath with wing-like lateral extensions, which may be lozenge- or wing-shaped (e.g., Albizia, Terminalia).
4. Confluent: aliform parenchyma of neighbouring vessels joined into irregular tangential or oblique bands (e.g., Acacia, Pterocarpus).
5. Unilateral: confined to one side of the vessel.
6. Paratracheal banded: bands that include the vessels (e.g., Artocarpus).

Phylogenetic significance: following Kribs (1937), the least specialised woods, which are associated with scalariform perforation plates and long tracheary elements, have diffuse apotracheal parenchyma, or very little of it. Evolution proceeded along two lines: from diffuse to diffuse-in-aggregates to banded apotracheal; and from scanty to vasicentric, aliform and confluent paratracheal. Paratracheal and banded types are advanced and occur with simple perforation plates and short vessel elements. The pattern therefore correlates with other xylem trends and helps judge the relative level of specialisation of a taxon and identify timbers. There are exceptions, since parenchyma also responds to ecology and function (storage and vessel refilling).

Ray parenchyma:

Primitive features:

1. Heterocellular rays made of both upright (square) and procumbent cells (Kribs' heterogeneous type I).
2. Tall rays of two sizes: both uniseriate and multiseriate rays are present, the multiseriate rays having long uniseriate wings or margins.

Advanced features:

1. Homocellular rays of procumbent cells only (homogeneous rays).
2. Storied rays in horizontal tiers (e.g., Pterocarpus, Dalbergia), or reduction of rays to short uniseriate rays only, or to multiseriate rays only.