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Inflorescences, Fruits and Seeds. So many, many terms… So little time…. Inflorescence. An inflorescence can be defined as the shoot system which serves for the formation of flowers and which is modified accordingly.
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Inflorescences, Fruits and Seeds So many, many terms… So little time…
Inflorescence • An inflorescence can be defined as the shoot system which serves for the formation of flowers and which is modified accordingly. • The inflorescence form and position is important in routine identification as well as in the determination of phylogenetic relationships.
Inflorescence Types • Two quite different inflorescence types occur in angiosperms. These are: • Determinate (monotelic) inflorescences • Indeterminate (polytelic) inflorescences
Determinate Inflorescence • The main axis of the inflorescence ends in a flower. • The flowering sequence of a determinate inflorescence usually begins with the terminal flower at the top of the cluster. • Determinate inflorescences are generally ancestral to indeterminate ones.
Indeterminate Florescence • The growing point produces only lateral flowers or partial inflorescences (groups of flowers). • The flowering sequence usually starts at the base (or outside) of the cluster.
Determinate Inflorescenses • The circles represent flowers and their sequence of opening (from large to small).
Determinate Inflorescences • Cymes are one of the most common types of determinate inflorescences. • The lateral branches of cymes are composed of usually numerous, three-flowered units usually showing opposite branching.
Some Common Kinds of Indeterminate Inflorescences • The circles indicate flowers; their size indicates the sequence of opening (from large to small).
Racemes and SpikesIndeterminate Inflorescence • A raceme is an inflorescence with a single axis bearing flowers with pedicels. • A spike is similar to a raceme but the flowers are sessile (lacking a pedicel or stalk).
Corymbs and PaniclesIndeterminate Inflorescence • A corymb is a raceme with the pedicels of the lowermost flowers elongated, bringing all of the flowers to the approximate same level • A panicle is merely a compound raceme, that has two or more orders of branches, with each axis bearing flowers or higher-order axes.
Head or capitulum • A head (or capitulum) is a dense terminal cluster of sessile flowers. • In a determinate head, the central flowers open first. • In an indeterminate head, the peripheral (outermost) flowers open first.
Umbel • An umbel is an inflorescence in which all of the flowers often have pedicels of approximately equal length that arise from a single region at the apex of the inflorescence axis. • Umbels are determinate if the flowers open from the center first and then proceed to the periphery. • Umbels are indeterminate if the flowers open from the periphery first and then proceed to the center.
More on inflorescences • Simple inflorescences have only a single axis (one order of branching). • Compound inflorescences have two or more orders of branching.
Catkin or Ament • Any elongated inflorescence composed of numerous inconspicuous, usually wind pollinated flowers. Willows have catkins.
Epiphyllous Flowers • Some flowers are borne on leaves.
Cauliflorous Flowers • Some flowers are borne on older stems or trunks.
Tendrils • Inflorescences are sometimes modified for climbing by becoming elongated and twining or developing adhesive pads, thus forming tendrils.
Fruit • A fruit is a matured ovary along with fused accessory structures (hypanthium or perianth parts). • There is great diversity of size, form, texture, means of opening, and anatomy among fruits. • Many structures that a botanist considers to be fruits are neither sweet nor good to eat! • Seed dispersal is the primary function of fruits.
Pericarpaka ovary wall • In some fruits, the pericarp becomes very juicy as it matures. Often, such a fruit has a high sugar content and is readily consumed by animals. • The pericarp in many other plants dries as it matures.
Pericarp • Often, the pericarp is dehiscent, splitting open and releasing the seeds that it contains. • In other plants, the fruit is indehiscent; the seeds remain enclosed within pericarp tissue.
Pericarp • The pericarp is often differentiated into layers, particularly in fleshy fruits. • The exocarp is the outer skinlike layer. • The mesocarp is the middle layer that often becomes soft and fleshy. • Only certain kinds of fruit have a third layer, the endocarp. This innermost layer closely surrounds the seed or seeds. (ie hard pit of olive or papery apple core). • A tomato is a fleshy fruit that does not have endocarp.
Simple Fruits • Simple fruits result from a single flower. • Simple fruits are divided into 2 categories. • 1) Those formed from a single carpel or several fused carpels. • 2) Those formed from several separate carpels of a single gynoecium (aggregate fruits).
Common Types of Simple Fruit • Fruit fleshy at maturity: • Berry – entire pericarp soft; generally with two or more seeds. Derived from either superior or inferior ovaries. Examples: tomato, banana, and grape. Includes the pome, the pepo, and the hesperidium.
Fruit Types associated with Berries • Pome – Derived from an inferior ovary and surrounded by a fleshy hypanthium. Restricted to the Rosaceae subfamily Maloideae. Examples: pear, apple, and quince. • Pepo – Derived from an inferior ovary with a leathery rind. Generally restricted to Cucurbiaceae family (watermelon, pumpkin, cucumber). • Hesperidium – Derived from a superior ovary with a leather pericarp having oil glands. The carpels are easily separated as segments that are lined with fleshy hairs. Restricted to Citrus and its close relatives (Rutaceae). Oranges, lemons, grapefruit.
Common Types of Simple Fruit • Fruits fleshy at maturity. • Drupe – Pericarp distinguishable as three layers: exocarp, mesocarp, and endocarp. The endocarp is a ‘stone’ that encloses the seed. Examples: peach, plum, cherry, coconut, olive.
Common Types of Simple Fruit • Fruit dry, one-seeded, not breaking apart at maturity. • Achene – Extremely variable in form. Seed and pericarp attached only by the funiculus (ovule stalk). Examples: buttercup, buckwheat. Includes also samara, cysella, and utricle.
Samara – A winged achene. Examples are elm, ash, and birch. • Cypsella – An achene with adnate calyx (pappus) Examples: members of the Asteraceae family such as the dandelion. • Utricle – A bladdery achene with the wall loosely surrounding the seed. Example: pigweed.
Common Types of Simple Fruit • Fruit dry, one-seeded, not breaking apart at maturity. • Caryopsis – Seed coat and pericarp completely adnate. Restricted to Poaceae family. Examples: maize, wheat, rye, barely, sorghum.
Common Types of Simple Fruit • Fruit dry, one-seeded, not breaking apart at maturity. • Nut - Exocarp hard; the fruit often subtended by an involucre (whorl of bracts). Derived from a syncarpous synoecium, but one-seeded by abortion of ovules. Examples: acorn, filbert.
Common Types of Simple Fruit • Fruit fleshy or dry, at maturity breaking into one- or a few-seeded segments, the seeds remain completely surrounded by the pericarp. • Schizocarp – Fruit breaking into one-carpellate segments (mericarps). Examples: members of the Apiaceae such as fennel and dill, and others such as hollyhock. Schizocarps may be winged (samaroid schizocarps) as in maple or fleshy as in madder.
Common Types of Simple Fruit • Fruit fleshy or dry, at maturity breaking into one- or a few-seeded segments, the seeds remain completely surrounded by the pericarp. • Nutlet – Friut deeply four-lobed, breaking into one-seeded half-carpellate segments; used especially for fruits of borage, vervain, and mint families. Examples: sage, borage.
Common Types of Simple Fruit • Fruit dry at maturity dehiscing either lengthwise, or by pores, teeth or a lid and exposing the seeds. • Capsule – Syncarpous and typically several- to many-seeded. Perhaps the most common and certainly the most variable of dehiscent fruits.
Septicidal capsule – Opens lengthwise along the septa. Example: zigadene. • Loculicidal capsule – Opens lengthwise between the septa and directly into the locule (evening primrose and iris). • Poricidal capsule – Opens by pores near the top (poppy)
Schizocarpic capsule – Breaks completely apart at the septa into one-seeded segments (castor bean). • Denticidal capsule – Opens apically by a ring of teeth (Eucalyptus, chickweed) • Circumscissile capsule – Opens horizontally in a ring so that a lid is formed (purslane, plantain, portulaca)
Common Types of Simple Fruit • Fruit dry at maturity dehiscing either lengthwise, or by pores, teeth or a lid and exposing the seeds. • Silique – A long, narrow (more than twice as long as broad) 2-carpellate fruit whose outer walls break away from a central papery partition. Restricted to Brassicaceae. Examples mustard, kale.
Common Types of Simple Fruit • Fruit dry at maturity dehiscing either lengthwise, or by pores, teeth or a lid and exposing the seeds. • Follicle – Unicarpellate, dehiscing along one suture (Examples: milkweed, larkspur).
