The Fruit The fruit is the mature gynoecium along with accessory tissues.

2. The Fruit The fruit is the mature gynoecium along with accessory tissues. As the fertilised egg develops, the gynoecium becomes the sole or main component of the flower. Perianth and stamens usually whither and fall. The style dries up, except in those species in which it functions in fruit dispersal. The ovary enlarges, but may be associated with noncarpellary tissue (accessory tissue) which dominates in the mature fruit. Parthenocarpy: fruits develop without fertilisation: may occur in citrus, pepper, pumpkin, tomato and produces seedless fruits. Seedless fruit may develop from aborted embryos, e.g. in cherry, grape, peach. Extracarpellary tissues: receptacle in strawberry, bracts in pineapple, calyx in the mulberry, and floral tube or receptacle in fruits derived from epigynous flowers, such as the apple and pumpkin. Simple fruit: formed from a single pistil (one carpel or two or more united carpels as in the bean pod, tomato, plum. Aggregate fruit: formed from an apocarpous gynoecium with each carpel maintaining its separate identity, e.g. raspberry, strawberry. Multiple fruit: derived from an inflorescence (combined gynoecia of many flowers) e.g. mulberry, pineapple. Accessory fruits (false or spurious fruits): any of the above fruit types which contains extracarpellary tissue, e.g. the apple is a simple accessory fruit; strawberry an aggregate accessory fruit; mulberry a multiple accessory fruit. If the fruit is defined to include any associated extracarpellary tissue then four fruit types encompass all fruit: 1. Aggregate fruit: carpels not united. 2. Unit fruit: carpels united. 3. Free fruit: formed from a superior ovary. 4. Cup fruit: formed from an inferior ovary embedded in a cup of noncarpellary tissue or from a superior ovary enclosed in a hypanthium. Combining these classifications: 1. Aggregate free fruit: derived from an apocarpous hypogynous flower. 2. Unit free fruit: from a syncarpous hypogynous flower. 3. Aggregate cup fruit: from an apocarpous perigynous flower. 4. Unit cup fruit: from a syncarpous epigynous flower. Fruitlet: an individual carpel in an aggregate fruit.

3. The Fruit Wall The pericarp is the mature ovary wall, the whole fruit wall is the pericarp plus accessory tissue. The pericarp may consist of three distinct layers (exocarp or epicarp, mesocarp and endocarp). Fruit Types Dry Fruit Dehiscent Fruit Dehiscent fruit commonly contain several seeds and may develop from a single carpel (follicle, legume) or from more than one carpel (capsule, silique). In monocarpellary dehiscent fruit, the break may occur longitudinally through the suture joining carpel margins, the back of the carpel or both simultaneously. In syncarpous fruits with parietal placentation, dehiscence may occur through the suture between two carpels or through the backs of carpels. In syncarpous fruits with axile placentation, the separation along the lines of union (septae) of joining carpels (septicidal dehiscence) may be combined with a breaking away from the central column. Dehiscence through the backs of carpels opens the locules (loculicidal dehiscence). Longitudinal breaks may occur in other places. Some fruits undergo longitudinal circular dehiscence involving all carpels (circumscissile dehiscence) or through pores (poricidal dehiscence). Many dehiscent fruit are called pods. Legumes (many Fabaceae) – derived from a superior ovary formed from a single carpel. Dehisces along the carpel margins and the median vein. In Glycine (soybean) pods, the exocarp is the outer epidermis and hypodermis, both with thickened walls; the mesocarp is parenchyma and the endocarp includes several layers of sclerenchyma and the inner epidermis. The cells in the hypodermis have their long axes perpendicular to those of the sclerenchyma. Thus, when the fruit dries, the outer and inner pericarp layers shrink in different directions, setting up stresses which open the fruit. This may be enhanced by the differing orientation of cellulose microfibrils in different layers of sclerenchyma. The valves may separate explosively and become twisted. In Phaseolus (bean) pod, the parenchyma beneath the hypodermis contains chloroplasts with starch granules and encloses a network of small vascular bundles near the sclerenchyma interconnecting the median and lateral bundles and makes some beans ‘stringy’. The inner epidermis of Phaseolus divides to form an inner layer of non-photosynthetic parenchyma, making the green pod a useful vegetable. In some legumes (Pisum, Vicia faba) the inner parenchyma produces multicellular hairs that extend into the locules and are thought to maintain optimum humidity inside the locules. Capsule (silique) – many Brassicaceae – consists of two carpels (bicarpellary) joined margin to margin and a false partition (derived from the marginal placentae) which divides the locule in two. The exocarp and mesocarp are thin-walled and the endocarp is sclerenchymatic. A rib develops around the partition, along the juncture of the carpels. The carpels separate along the suture, leaving the seeds attached to the ribbed edge or frame (replum) of the partition. E.g. shepherd’s purse (Capsella).

4. Follicle: a dry monocarpellary, superior, one-chambered fruit that dehisces by one suture only. E.g. the simple follicle of madar (Calotropis). Most often follicles are aggregates. Diagrams of cross sections of dry dehiscent fruits illustrating three types of fruits, still unopened (A, D, G), and examples of dehiscence of such fruits (B-C, E-F, H-I). A, single carpel. D, three carpels, parietal placentation. G, three carpels, axial placentation. The median and two lateral bundles are indicated in each carpel. The median bundles are shown split in two in C, F, I.

6. Indehiscent Fruit Usually derived from an ovary in which only one seed develops, even if more than one locule is present. The pericarp resembles a seed coat in structure and may largely replace the seed coat (achene of Asteraceaea) or fuse with the seed coat (caryopsis of Poaceae). Achene (Asteraceae): develops from an inferior ovary (a cypsella). One-chambered, one-seeded fruit developing from a superior or inferior monocarpellary ovary and with a pericarp free from the seed coat. The floral tube forms extracarpellary tissue (indistinct from the pericarp). The seed coat (derived from one integument) has a thick-walled outer epidermis and the fruit wall is reduced to an outer sclerified tissue and some parenchyma. E.g. the simple achenes of hogweed (Boerhaavia); most are aggregate. Caryopsis (grasses, monocarpellary, superior, pericarp fused with seed coat). The pericarp and remains of the seed coat from the outer layers of the wheat caryopsis. The layers are: outer epidermis (covered by cuticle), one or more layers of parenchyma, partly resorbed parenchyma, cross cells (elongated transverse to the grain long axis and having thick lignified walls) and remains of an inner epidermis (lignified cells elongated parallel with the grain long axis – tube cells). The outer integument disintegrates and the inner becomes altered and compressed – it is covered by cuticle on both sides and contains a fatty pigment. The endosperm forms 83% of the fruit and contains starch and protein. The outermost endosperm layer is the aleurone layer which contains lipids and proteins. Wheat bran: 14% of the grain, includes the pericarp, remnants of the nucellus and integuments, and the aleurone layer. Wheat germ: the oily wheat embryo. Glutens: wheat proteins that affect bread making along with glycolipids which interact with the glutens. Zea (including maize): the outer pericarp consists of cells with thick pitted walls and is compressed. The central pericarp disintegrates. The inner pericarp remains thin-walled and is compressed, stretched or torn. The integuments disintegrate completely A cuticle occurs between the thick-walled nucellar epidermis and the pericarp. Cuticular layers in the seed coat are derived from the nucellar epidermis and the integuments and are fused into one layer. In wheat, a strand of pigmented tissue interrupts this layer and this may allow water to enter the seed (?). Millet (Echinochloa utilis): a small gap in the cutinised seed coat occurs at the base of the caryopsis and contains two cell types – nucellar cells and cells similar to those in the wheat pigment strand. The aleurone cells opposite these nucellar cells are transfer cells with wall ingrowths. Similar aleurone transfer cells occur in Zea. Cypsela: a dry, one-chambered and one-seeded fruit developing from an inferior, bicarpellary ovary with free pericarp and seed coat, e.g. Compositae: sunflower, marigold. Samara. A dry, indehiscent, one or two seeded fruit developing from a superior bi- or tricarpellary ovary, with one or more flattened, wing-like outgrowths, e.g. ash. The wings develop from the pericarp and the fruit splits into fruitlets, each enclosing a seed. Samaroids: winged fruit, but with the wings derived from dry, persistent sepals, e.g. wood-oil tree (Dipterocarpus), sal tree (Shorea) and Hopea.

7. Caryopsis (A) of wheat (Triticum) and parts of its pericarp in longitudinal section (B) and surface views (C, D).

8. Samaras of elm, maple and sycamore.

9. Nut. A dry, one-chambered and one-seeded fruit, developing from a superior, bi- or polycarpellary ovary, with a hard and woody pericarp. E.g. chest-nut (Castanea), oak, beech. Schizocarp (Schizocarpic fruit) Lomentum. A dry indehiscent legume with partitions between the seeds and one seed per compartment. The fruit splits transversely into one-seeded fruitlets, e.g. gum tree (Acacia), sensitive plant, Indian telegraph plant (Desmo-dium gyrans). Cremocarp. A dry, indehiscent, two-chambered fruit developing from an inferior, bicarpellary ovary. The fruit splits into indehiscent one-seeded fruitlets, called mericarps. The mericarps remain attached to the prolonged end (carpophore) of the axis. E.g. Umbelliferae: coriander (Coriandrum), cumin (Cuminum), anise or fennel (Foeniculum), carrot (Daucus). E.g. the cremocarp of Carum (Apiaceae) – derived from an inferior ovary. Pericarp and accessory tissue can not be distinguished. The mericarps separate such that the united lateral bundles and associated tissue form a column, forked at the top. Double Samara. Maple (Acer) – develops from a superior, bicarpellary ovary. Splits into two samaras when mature, each with one wing and one seed. Regma. A dry, indehiscent fruit developing from a syncarpous pistil. It splits away from the central axis into cocci, each coccus containing one carpel and one or two seeds. The dry pericarp decays to liberate the seeds, e.g. caster (Ricinus), Geranium. Carcerule. A small, dry, indehiscent, four-chambered fruit developing from a superior, bicarpellary pistil and is enclosed by a persistent calyx and splits into four nutlets, each enclosing a single seed. E.g. Labiatae.

10. Fleshy Fruits Drupe (stone-fruit). A fleshy fruit with one or more chambers and one or more seeds developing from a monocarpellary or syncarpous pistil. The pericarp consists of epicarp (skin), mesocarp (often fleshy) and the endocarp (hard and stony). E.g. mango (Mangifera), plum and peach (Prunus), coconut-palm (Cocos). The fruit of Prunus originates from a single carpel in a perigynous flower. The ventral suture between the carpel margins is often visible as an indentation in plums, peaches and nectarines. The thin exocarp consists of epidermis and subepidermal collenchyma, the mesocarp is fleshy and the sclerenchymatous endocarp is stony. Bacca (Berry). A many-seeded fleshy or pulpy fruit developing from a single carpel or a syncarpous pistil, e.g. tomato, gooseberry, grapes, banana. The seeds separate from the placentae in the ripe fruit and remain free in the pulp. Date palm is a one-seeded berry. The banana (Musa acuminata) fruit arises from an inferior tricarpellary ovary with axile placentation. In seedless parthenocarpic bananas the ovules degenerate and the locules are filled with starch-rich pulp originating from the pericarp and dividing walls. Very little pulp is produced in seeded varieties as the mature seeds fill the locules. The parenchyma of banana fruit walls contains numerous vertical vascular bundles and laticifers. Inside this zone occurs aerenchyma, and then a zone with horizontal vascular bundles that connect with the pericarp vertical bundles and the central carpellary bundles. In the tomato (Lycopersicon esculentum) the berry has no rind. Wild types and cherry tomatoes have two carpels, but other cultivated forms have a variable larger number of carpels. The fleshy tissue includes the pericarp, the partitions and the placentae (which are axile, but fill most of the locular space). Placental tissue that invades spaces among the ovules becomes gelatinous when the fruit is mature. Absorption of red light by phytochrome and ethylene synthesis cause the green chloroplasts to change in to red chromoplasts. Pepo. A fleshy, pulpy many-seeded fruit which develops from an inferior, unilocular or trilocular syncarpous pistil with parietal placentation. E.g. Cucurbitaceae (cucurbits): cucumber, melon, squash, etc. The seeds lie in the pulp, but remain attached to the placentae. The boundary between carpellary and extracarepellary tissues is not discernible. A single-layered epidermis is covered with cuticle and has stomata. The subepidermal consists of parenchyma or collenchyma. The subepidermal parenchyma give the fruit its colour and may have green chloroplasts or yellow chromoplasts. Fibers and phloem strands may be present and in some there is a layer of sclereids. Beneath this sclerenchyma is parenchyma which extends to the centre of the fruit at maturity (cucumber, water melon) or id torn and replaced by a central cavity (Cucurbita maxima, muskmelon). The inner epidermis of the endocarp may cover the seeds in a membranous layer. In water melon the red colour results from pigment crystals inside chromoplasts. Pome. An inferior bilocular or multilocular, fleshy, syncarpous fruit surrounded by the thalamus. The thalamus constitutes the fleshy, edible part. E.g. apple, pear.

11. The fruit of Pyrus (P. malus, apple; P. communis, pear), the pome, arises from an inferior ovary and the bulk of the flesh is extracarpellary. This extracarpellary tissue is interpreted as either part of the floral tube or hypanthium or as derived from the receptacle. The ovary consists of five carpels united to form axile placentation. The outer epidermis is covered with a thick cuticle of overlapping platelets of wax. Stomata and trichomes occur in young fruit. The stomata are later replaced by lenticels. In “russeting” apples patches of cork develop in the outer layers of the apple. The subepidermal tissue is compact and has thickened walls. The skin is made up of the epidermis and subepidermis. The skin of red varieties contains anthocyanins and carotenoid-rich chromoplasts also contribute to the red colour. The flesh is mostly parenchyma with large air spaces and contains the main bundles which give off anastomosing branches throughout the flesh. The core consists of parenchyma enclosing the median and lateral carpellary bundles and an endodermis of sclereids lining the locules. Each locule has two or more seeds. Clusters of sclereids in the flesh of the pear.

13. Transactions of fruits of Musca acuminata (banana, A, B) and Lycopersicon esculentum (C). A, parthenogenesis carpic fruit with ovarian cavities occluded by pulp derived from pericarp and partitions. B, seeded fruit with ovarian cavities occupied by seeds and small amount of pulp. C, the placentae have occluded the locules and have embedded the ovules. The tissue among the ovules of gelatinous in mature fruit. Solid black lines indicate lacunar spaces. Hesperidium. A superior, multilocular, fleshy fruit developing from a syncarpous pistil with axile placentation. The endocarp (and mesocarp) projects inwards to form distinct chambers and the fused epicarp and mesocarp form the rind, e.g. Citrus with about ten carpels. In lemon the exocarp (flavedo, the yellow tissue) consists of cuticle-covered outer epidermis and compact subepidermal parenchyma with oil glands and crystal-containing cells. The mescocarp of lemon (albedo or white tissue) consists of parenchyma with large intercellular spaces and aerenchyma and contains a vascular network. The endocarp consists of inner epidermis and a few layers of compact parenchyma. (Peel: exocarp and all but innermost layer of mesocarp). The endocarp produces the juice sacs (multicellular club-shaped structures with long stalks) that fill the locules. In a mature juice sac a cuticularised epidermis encloses large vacuolated cells containing juice. Photosynthetic parenmchyma gives the exocarp of unripe fruit its green colour. These chloroplasts become chromoplasts in the ripe fruit (the Valencia orange is orange in winter and turns green again in spring). Balausta. Inferior, many-chambered and many-seeded fruit developing from a syncarpous pistil with usually two whorls of basal carpels within the receptacle, forming two layers of chambers. The pericarp is tough and leathery and the chambers are made of thin-walled carpels, e.g. pomegranate (Punica granatum).

14. A, transection of ovary of Citrullus vulgaris (watermelon). The dashed lines indicate regions of union of carpels, solid lines delimit margins of carpels within each carpel and the placentae from the fruit wall. The lateral bundles of contiguous carpels are united. B, transection of one carpel with one placenta freed from the surrounding tissue. C, a diagram interpreting the arrangement of carpels in a cucurbitaceous ovary.

15. Fruit of Prunus domestica (prune). A, longitudinal and B, transverse sections of the ovary. Ovarian cavity in solid black. C, D, outer part of pericarp 6 weeks after full bloom (C) and 2 weeks after abscission. Disorganised protoplasts and partly collapsed cell walls in D. E, F, inner part of endocarp. E, 6 weeks after full bloom, at completion of cell division. F, 8 weeks after full bloom, at beginning of lignification. C-F from transverse sections.

16. Citrus fruit. A, B, young ovary from flower of Citrus aurantifolia (lime) in longitudinal (A) and transverse (B) sections. C, part of transection of young fruit of Citrus sinensis (orange) including one carpel. Juice sacs in early stage of growth. D, diagram of orange fruit including two carpels and part of a third. Juice sacs fill the locules.

17. Aggregate Fruits An aggregate of simple fruits borne on a single flower is called an etaerio. Etaerio of follicles, with two or more follicles, e.g. madar (Calotropis) and periwinkle (Vinca). Etaerio of achenes. E.g. Clematis, Rannunculus, strawberry, rose, lotus. Etaerio of drupes. E.g. raspberry (Rubus) with small drupes (drupels or drupelets) aggregated together in a fleshy thalamus. Each drupelet has a stony endocarp of various layers of differently oriented elongated sclereids and the succulent pulp is the parenchymatous mesocarp. The exocarp bears epidermal hairs that hold the drupelets together at maturity. Etaerio of berries. Berries embedded in the fleshy thalamus, e.g. custard-apple (Annona squamosa) or with distinct and separate berries, e.g. Polyatlhia, Artabotrys. Multiple or Composite Fruits (infructescence) A composite fruit develops from an inflorescence. Sorosis. A multiple fruit developing from a spike or spadix. The flowers fuse together by their succulent sepals and the axis grows fleshy or woody and the whole inflorescence forms into a compact mass, e.g. pineapple. Mulberry is a sorosis with the fleshy part made of loosely attached sepals. Syconus. Develops from a hollow, pear-shaped, fleshy receptacle which encloses a number of minute male and female flowers. The fleshy receptacle encloses a number of achenes, e.g. Ficus (e.g. fig, banyan). Longitudinal section of the flower of Rosa.

18. Blackberry (Rubus); a, the polycarpellate gynoecium; b, carpel; c, median section of the aggregate fruit; d, young drupelet; e, mature drupelet; h, hypanthium; s, sepals; st, stamens.

20. Dispersal of seeds and Fruit Seeds and Fruits Dispersed by Wind Wings. E.g. maple and sycamore (Acer), elm and birch. Parachute mechanism. In many Compositae, the calyx forms a pappus of hairs. The pappus opens out in an umbrella-like manner when the fruit detaches from the parent plant. E.g. cotton. Censer mechanism. The seeds are discharged from a dehisced fruit when the fruit is shaken by the wind. E.g. poppy (Papaver), loofah (Luffa). Hairs. The seeds of madar (Caloptropis), milkweed (Asclepias) and cotton have hairs either in one or two tufts or all over the seed. Persistent styles. In Clematis the styles persist and are very feathery. Light seeds and fruits. Orchids have the smallest seeds. Millions of dust-like seeds are produced in a capsule. The fruits of some grasses are also very light. Seeds and Fruits Dispersed by Water The fibrous coat of the coconut is a flotation device that carries the coconuts across the sea. In the double coconut (coc de mer, Lodoicea maldivica) the fruit weighs 18 kg and may be up to a metre in length and takes 6-10 years to ripen. In lotus, the spongy thalamus, bearing fruits and its hemispheric top, floats in water. The seeds of water lily are small and light and also have an aril enclosing air and so they can float on water. Seeds Dispersed by Explosive Fruits Scatter seeds a few yards from the parent plant, e.g. balsam (Impatiens), wood-sorrel (Oxalis). Some seeds of the explosive fruits of Acanthaceaea are provided with jaculators (curved hooks) that suddenly straighten and help seed ejection. The fruits may burst open in either dry or wet conditions, depending on species. Camel’s foot climber (Bauhinia vahlii) has long explosive pods sometimes exceeding 30 cm in length. Seeds and Fruits Dispersed by Animals Hooked fruits. Hooks, bristles, spines, barbs, stiff hairs etc. allow the fruit to adhere to fur and clothes. Sticky fruits. These have sticky glands, e.g. Plumbago, mistletoe (Viscum). Fleshy fruits and edible fruits. Animals eat the fruit and seeds pass out with their faeces, e.g. guava, grape, fig, dates, plums. Squirrels may disperse acorns and hazelnuts when they bury them for a winter store which they later forget about or do not need.