Seeds and Fruits Types & Dispersal

Seeds and Fruit Fruits are formed by seed plants to aid in dispersing seeds A seed contains the developing plant embryo in a protective coat (testa) Seeds form from ovules fertilized in the ovary Ovaries with seeds ripen into dry or fleshy fruits

Parts of a Seed External seed coat or testa Developing plant embryo Stored food called endosperm Seeds may be in one part (monocot) or two parts (dicots) DICOT MONOCOT

Parts of a Seed

Gymnosperm Seed A single fertilization produces the diploid (2n) embryo The food source is the haploid megagametophyte

Dicot vs. monocot seed Dicot has two cotyledons (like bean) Monocot has one cotyledon which absorbs the endosperm tissue during germination (corn)

Fruit In flowering plants – Fruit is a mature, ripened ovary that contains the seeds Pericarp – the ovary wall ovary Fruit types A. Simple B. Aggregate C. Multiple

A. Simple fruit A. Simple fruit – develops from a ripened ovary of a single flower. Simple fruits can be either fleshy or dry when mature

Simple fleshy fruit 1. Berry – entire fruit wall is soft and fleshy at maturity. Inside is slimy. For example, grapes, tomato, etc.

Simple dry fruit: capsule Simple dry fruits are dry (not fleshy) at maturity. Simple dry fruits that open at maturity include: capsules and legumes Capsule – fruit is dry at maturity and splits open along several seams Example: Cotton

Simple dry fruit: Legumes Legumes are dry at maturity and split open Examples: pea pods, bean pods, peanut

Simple dry fruits Simple dry fruits that do NOT open at maturity include Caryopsis: seed coat is fused to the ovary wall (cereal grains like wheat) Nuts: single-ovary wall and seed coat remain separate, ovary wall is very hard (acorns)

C. Multiple fruit Multiple fruit develops from ovaries of several flowers borne/fused together on the same stalk For example: Pineapple

What is the purpose of the fruit? The main function of the fruit is to disperse the seeds Dispersal is important because 1. It spreads the progeny in order to colonize new environments 2. Reduces competition for resources with parents 3. Reduces the chances of predators destroying all of the plant’s yearly seed production Four types of seed dispersal: A. Self dispersal B. Wind dispersal C. Water dispersal D. Animal dispersal

A. Self dispersal Plants disperse their seeds by forceful ejection – explosive fruits! Witch hazel, squirting cucumber (jet propulsion)

Self dispersal The peanut plant sows (buries) its own seeds! Geocarpic: carpel grows inside the earth (soil)

B. Wind dispersal Fruit and seeds may have special devices for wind dispersal Plumes catch wind currents: Dandelion Trees take advantage of their great heights for wind dispersal. Fruits with wings are used to slow the descent to land: maple, ash fruit

C. Water Dispersal Fruits and/or seeds use flotation devices to travel by water (in rivers, oceans, etc.) Fruit may have air spaces and corky floats: for example coconuts.

D. Animal dispersal Many plants depend on animals for seed dispersal; they may offer a nutritional reward Animals learn to recognize ripened fruit colors Fleshy fruits eaten and dispersed with feces

Animal dispersal Some dry fruit attach and cling to animals (they hitchhike on the animals) Some have Velcro-like hooks that cling to animal fur (burdock, cockleburs) Others have sticky substances that stick to host (mistletoe)

A few plant images you should know!