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

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

Plant Life Cycle, Fruits and Seeds

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. 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 are types of hesperidia. The individual sections are the carpels. The fluid filled vesicles are actually modified gland cells.

vesicles

carpel

carpel

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 silique (mustard)

a legume (pea) a follicle

(larkspur) a capsule (poppy)

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

Samaras

Achene

Nuts Caryopsis

Carpels enclosing seeds evolved from more primitive leaf-like 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