Lecture 14 Seeds and Fruit Seeds Fruits Fruit types Seed dispersal Video seed dispersal Real fruit samples What is a seed A matured ovule containing 1 a plant 2 a food supply 3 covered by a Embryo The seed contains a well formed multicellular young plant embryo germ Embryo is 2n It will become a whole plant Nutritive tissue Seed contains a food supply Stored food contains enough energy for the embryo to grow through the soil when seedling is unable to photosynthesize Food source can be the which is n as a result of double fertilization Seed coat A thick protective coat outer layer of the seed Formed from the Seed coat Gymnosperm seed Single fertilization produces the diploid embryo 2n Food source is the haploid megagametophyte Flowering plant seed In angiosperms flowering plants there is DOUBLE Which produces a diploid 2n and A triploid 3n Endosperm is the food source Dicot vs monocot seed Dicot has two cotyledons like bean Endosperm food is kept in the Monocot has one which absorbs the endosperm tissue during germination corn Fruit In flowering plants Fruit is a mature ripened o that contains the seeds Pericarp the ovary wall Fruit types A Simple B Aggregate C Multiple ovary A Simple fruit A Simple fruit develops from a ovary of a single flower Simple fruits can be either fleshy or dry when mature Simple fleshy fruit 1 2 Hesperidium 3 4 Pepo 5 Simple fleshy fruit 1 Berry entire fruit wall is soft and fleshy at maturity Inside is slimy For example grapes tomato etc 2 is a berry with tough leathery rind peel Examples oranges lemons other citrus Simple fleshy fruit drupe 3 type outer part of fruit wall is soft and fleshy inner part is hard and stony For example Simple fleshy fruit pepo 4 also a fleshy fruit with a tougher outer rind All member of the squash family pumpkin melons cucumbers Simple fleshy fruit pome 5 Pomes most of the fleshy part of pomes develops from the enlarged base of the perianth corolla and calyx that has fused with the ovary wall Pomes include 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 along seams 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 Nuts single ovary wall and seed coat remain separate ovary wall is very hard acorns B fruit develops from one flower with many separate pistils carpels all ripening simultaneously Examples strawberry raspberries blackberries C Multiple fruit Multiple fruit develops from ovaries of several flowers borne fused together on the same stalk For example 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 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 dispersal C Water dispersal D 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 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 D Animal dispersal Plants have with animals to accomplish seed 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 Video on seed dispersal Watch the video take notes answer these questions What carries the dandelion seeds for miles What feature of trees gives them a particular advantage when dispersing seeds by air How does the squirting cucumber disperse its seeds Although plants use wind and water what do most plants use as carriers for their seeds Blackberries on a tree do not ripen simultaneously why What plant do elephants help to disperse How do they do it What percentage of these seeds germinate in elephant dung Why
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