Plant Life Cycle, Fruits and Seeds Fruits All flowering plants form some type of fruit Botanically, a fruit is the modified, ripened ovary of an angiosperm, together with any accessory structures that may be present Fruits are distinctive, unique to angiosperms Following fertilization, seed begins to mature Endosperm cells divide Ovary enlarges, swells, elongates as seeds mature Integuments surrounding ovule become seed coat Pericarp tissues surrounding ovule differentiate three layers: exocarp, mesocarp, endocarp fleshy or tough, depending on plant species Pericarp tissue has evolved to form diversity of fruit types Fruits may develp without fertilization (parthenocarpic) and are usually seedless
Plant Life Cycle, Fruits and Seeds Fruits have specialized structures adapted for different types of dispersal Functions of fruits protect seeds seed dispersal wind dispersal light weight, winged seeds water dispersal buoyant, waterproof animal dispersal barbs, hooks, sticky substances fleshy, edible fruits have small seeds that survive animal gut have large or medium size seeds with hard outer layer Fruits used by humans for food are derived from wild, animal dispersed fruits Multiple cycles of breeding and selection for desirable traits
Variations of fruits
Types of Fruits Simple fruits develop from the ripening of an ovary of a single carpel In some plants fused carpels have evolved from ancestor plants that had multiple carpels, these also are considered to have simple fruits
Compound Fruits include: Aggregate fruits develop from the ripening of multiple separate carpels of a single flower Multiple fruits develop from multiple separate flowers of a single inflorescence. The individual fruits grow together and fuse during development.
Simple Fruits Berry: is a simple fruit with a fleshy mesocarp and an endocarp enclosing one or more seeds Note: raspberries and strawberries are not (botanically) berries. tomatoes are berries, melons are a type of berry, as are cucumbers, oranges and limes.
carpel
A pepo is a berry with a tough exocarp. Cucumbers, squash, pumpkins, melons, gourds are pepos. The exocarp includes some tissue derived from the flower receptacle. A hesperidium is another type of berry that has a leathery outer rind. Oranges, lemons, limes carpel are types of hesperidia. The individual sections are the carpels. The fluid filled vesicles are actually modified gland cells. vesicles
Simple Fruits A drupe is the type of fruit of cherries, plums and peaches. The seed is encased in a hard, stony endocarp. A pome is the type of fruit of apples and pears. The fleshy part of the fruit does not develop from the pericarp tissue, it develops from the perianth (calyx and corolla of the flower). Pomes are accessory fruits because tissues other than the pericarp are part of the mature fruit.
Aggregate Fruits Aggregate fruits develop from a single flower that has multiple carpels. Raspberries and blackberries are aggregate fruits with a thin exocarp, fleshy mesocarp, and a seed enclosed in the endocarp. Individual raspberry fruits are drupelets. Strawberries are aggregate accessory fruits. The fleshy part of the fruit develops from receptacle tissue (flower). The “true� fruits of a strawberry are the individual achenes on the outside.
Multiple Fruits Multiple fruits develop from the fusion of multple flowers in a single infloresence. Figs, pineapples, jackfruit and breadfruit are examples of multiple fruits.
Dry Fruits Dehiscent dry fruits At maturity the fruit tissue derived from pericarp is dry, tough Dehiscent fruits split open to release the seeds Various types of dehiscent dry fruits are distinguished botanically Capsules open by small pores or slits Follicles split along one edge Legumes split along two edges Siliques develop from two fused carpels and split open along the septum seeds are attached to the septum Carpels evolutionarily derived from leaves, some resemble a folded fused leaf or group of fused leaves
a capsule (poppy)
a follicle (larkspur)
a legume (pea)
a silique (mustard)
Dry Fruits Indehiscent dry fruits The tissues derived from the pericarp that surround a seed do not open Various botanical types Achenes have a single seed separate from surrounding pericarp, a dry berry Samaras are achenes with part of the pericarp elongated to form a wing Nuts have a single seed with a hard, stony pericarp Grain or caryopsis is the type of fruit produced by cereals in which the pericarp is fused to the seed coat
Achene Samaras
Nuts
Caryopsis
Carpels enclosing seeds evolved from more primitive leaflike reproductive structures
Cross section of a pepper fruit, a type of berry
seed structure of a monocot
Most of seed is occupied by endosperm, nourishes seedling during germination Seed coat is fused to pericarp--compare to an achene in which the seed is separate Single cotyledon (scutellum) Epicotyl and radicle have covering tissues, coleoptile and coleorhiza
seed structure of a dicot
Nutrient reserves are stored in cotyledons rather than endosperm Most of seed volume is occupied by the two cotyledons Seed coat is not fused to wall periderm, the ovary tissues that form the fruit No coleoptile or coleorhiza
Fruits of Temperate Regions Rosaceae - apples, pears, plums, cherries, peaches, strawberries, blackberries, raspberries Different fruit types: pome, drupe, aggregate Apples & pears subfamily Maloideae Apples, pears, quinces Apples are a major world crop, account for about 60% of temperate tree fruit production Originated in Asia, spread to North America prior to human arrival Many varieties are known and have been selected since early humans Romans had >20 named varieties Apple varieties selected for various charaters taste and texture early vs late ripening storage survival production Propagated by grafting shoots of select trees on rootstock