Plant Physiology and Development - Fruits and Seeds PDF

PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT E. FRUITS AND SEEDS I. Description, Functions, and Parts of fruits and seeds II. Forms and modifications of fruits and seeds III. Economic, environmental, and medicinal uses of fruits and seeds FRUIT - th...

PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT E. FRUITS AND SEEDS I. Description, Functions, and Parts of fruits and seeds II. Forms and modifications of fruits and seeds III. Economic, environmental, and medicinal uses of fruits and seeds FRUIT - the swollen, fertilized and ripened ovary of the flower, the last step in the process of sexual reproduction of flowering plants. Pollination → seed formation / Fertilization → tissue formation → Fruit Fruits help the plant to disperse the seeds, through different mechanisms that depend on the type of fruit. Animals who eat fruits will often disperse the seeds to other areas. Some dry fruits can attach themselves to the feathers and fur of animals and “catch a ride” to another area where they can grow without competition. Other fruits resemble wings and will fly with the wind. I. PARTS OF A FRUIT A fruit is composed of both pericarp (fruit wall) and seed. 1. SEED/S - the seeds are protected inside fruit. - But in some fruits, seeds are not found (like in grapes, banana and such type of fruits are seedless fruit.) ** Parthenocarpic fruit - a fruit formed without fertilization of the ovule. - Since there is no fertilization, such fruits are seedless. - Banana is an example of parthenocarpic fruit. 2. PERICARP - After ripening, the ovary wall changes into pericarp. - This pericarp may be thick and fleshy or thick and hard or thin and soft. The pericarp is differentiated in 3 layers: 1. Epicarp/Exocarp: It is the outermost layer, which is also called “rind”. 2. Mesocarp: It is the middle layer. 3. Endocarp: It forms the innermost layer. * True Fruit: When the fruit is developed only from the ovary, the fruit is called as true fruit. * False Fruit or Pseudocarp: In some fruits, in place of ovary, some other parts of flower like thalamus, inflorescence, calyx are modified to form a part of fruit. - Cashew-nut, which develops from the peduncle. - Apple, pear, and cucumber, which develop from the thalamus. - Jackfruit and pineapple, which develop from the entire inflorescence. The way most people use the word fruit and the way that botanists use the word fruit can be quite different. In nonscientific terms, people tend to think of fruits as sweet. But to a botanist, any ripened ovary is a fruit. So, while it’s true that apples, oranges, and grapes are fruits, so are tomatoes, nuts, cucumbers, string beans, maple “helicopters,” grains of grass, and acorns. Botanically, the term vegetable pertains specifically to plant parts that are edible such as leaves, roots, stems, flowers, etc. Plant parts such as edible fruits and seeds are not considered as vegetables. Rather, they are referred to as their name implies. JSBW’23 1  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT II. CLASSIFICATION OF FRUITS A. SIMPLE FRUIT: - These fruits develop from monocarpellary ovary or multicarpellary syncarpous ovary. - Only one fruit is formed by the gynoecium. Simple fruits are of two types – Fleshy fruit or Dry fruit 1. Fleshy fruits - the mesocarp is soft or fleshy when the fruit is ripe. - Simple fleshy fruits form from flowers that have one pistil with either a simple or compound ovary. a. Drupes - are fleshy fruits with a single seed protected by a hard, stony endocarp called a pit. - Coconuts are an unusual example of a drupe — the husk that many people never see is the exocarp and mesocarp of the fruit. The coconuts sold in stores are just the pit of the coconut fruit with the hard endocarp and seed within. b. Berries - usually develop from compound ovaries and contain multiple seeds. - endocarp of berries is fleshy like the rest of the pericarp, so it’s difficult to tell this layer from the rest. - True berries have a thin skin and are soft when ripe. → tomatoes, grapes, and peppers, - Pepos are berries with a thick skin, or rind, → pumpkins and other squash. - Hesperidium are a type of berry that has a leathery, oily skin. → Oranges, lemons, and other citrus fruits c. Pomes - form when the fruit receptacle enlarges and grows up around the ovary, becoming part of the fruit. - endocarp of pomes forms a papery or leathery layer around the seeds. - In apples, the ovary itself becomes the core of the apple, while the rest of the apple develops from the receptacle. ** Botanists also call fruits like apples accessory fruits because part of the fruit develops from a part of the flower other than the ovary itself. 2. Dry fruits - have a dry mesocarp when the fruit is mature. - Some dry fruits, called dehiscent fruits, split open when they’re ripe, releasing the seeds. - Other dry fruits, called indehiscent fruits, stay intact. Simple dry fruits can be divided into following three groups: a. Indehiscent fruits - simple dry fruits are generally of small size and single seeded pericarp does not rupture even after maturity. JSBW’23 2  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT a1. Achenes - have seeds that are attached to the pericarp only at the base. - Sunflowers produce achenes. Because the seeds are attached to the husk at only one point, it’s relatively easy to pry the seeds out and eat them. a2. Nuts - have one seed, but they are larger than achenes, and they have a thick, hard pericarp. - True nuts, such as acorns or filberts, have a cup or cluster of bracts at their base. **Many foods that people commonly call nuts, aren’t really nuts — botanically speaking. Peanuts are legumes; almonds, cashews, pistachios, and macadamia nuts come from drupes; and Brazil nuts are seeds from a capsule. a3. Grains or caryopses - have seeds that are tightly joined to the pericarp so that they can’t be separated from each other. - All members of the grass family, including wheat, corn, barley, rice, and oats, make grains. a4. In samaras, - the pericarp forms wings that extend out from the seeds. - The winged fruits of maple trees are a common example of samaras. b. Dehiscent fruits: - After ripening pericarp are ruptured and seeds are dispersed outside. b1. Legumes - split open along two sides. → Beans, peas, carob, and mesquite all produce legumes. b2. Siliques - also split open along two sides, but the seeds initially stay attached to a central partition inside the fruit. - Siliques tend to be long and thin. - Fruits that open the same way as siliques, but are shorter and wider, are called silicles. → mustard family, such as broccoli, radishes, and cabbage. b3. Capsules - can split open in a number of different ways. - Some capsules, like those of iris plants, split open along the partitions between the chambers of the ovary. - Others form a cap at one end that may pop off to release the seeds. - The capsule of poppy flowers develops holes in the cap through which the seeds can be shaken out. c. Schizocarpic fruit: - It is a multiseeded fruit. - Schizocarps split into two halves when they are mature, but the seeds remain inside the fruit. → Carrots, dill, and caraway all make schizocarps. JSBW’23 3  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT II. AGGREGATE FRUIT: - Aggregate fruits form from single flowers that have multiple pistils. - Each pistil develops into a fruitlet, and all the fruitlets are clustered together on a single receptacle. - Raspberries, blackberries, and strawberries are all aggregate fruits (and not really berries at all). - The part of the strawberry that gets red and juicy is actually swollen receptacle, and the little hard seed-like things on the outside little fruitlets called achenes. Because the receptacle forms part of the fruit, botanists call it accessory tissue. III. MULTIPLE FRUIT: - Multiple fruits develop from multiple flowers in a single inflorescence. - The ovaries of the individual flowers develop into fruitlets that grow together to form one, larger fruit. - Pineapples are an example of a multiple fruit — each little diamond-shaped section that you see on the outside of a pineapple represents one of the original flowers in the inflorescence. All the fruitlets fused together to form the larger pineapple. SEEDS I. DESCRIPTION - Seeds are mature ovules found inside the mature ovary of a plant. - They are efficient structure for reproduction and multiplication because seeds have protective coverings and food reserves, helping them to survive away from the parent plant. - Seeds can remain dormant for hundreds, or even thousands of years, before they begin to grow. - Seeds germinate, or begin to grow, when conditions are right for the new plant. The amount of time seeds remain dormant depends upon a combination of internal signals, such as hormones and external signals from the environment, such the temperature and the availability of light and water. - Some seeds germinate within weeks of being released from the parent plant, while others may remain dormant for months to years. Over time, seeds will begin to die if they don’t encounter the right conditions for growth. JSBW’23 4  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT Two groups of plants have the ability to make seeds, these are gymnosperms and angiosperms. 1. Gymnosperms are plants that make seeds, but don’t make flowers and fruits. Gymnosperms often package their seeds in cones. Gymnosperms include pine trees, Ginkgo trees, and cycads. 2. Angiosperms are plants that make seeds, flowers, and fruits. In other words, angiosperms are the familiar flowering plants. Two groups of plants — monocots and dicots — within the angiosperms have distinct structural differences, both in their vegetative and reproductive structures. Botanists define these two groups of angiosperms based on the number of seed leaves, or cotyledons, that are attached to the plant embryo within the seed: a. Monocots have one cotyledon. An example is corn. b. Dicots have two cotyledons. Examples are bean and peanut II. SEED STRUCTURE 1. Seed coat – develops from the integuments of the ovule; tough and partly impervious to water - other visible structures: a. Hilum – scar left by breaking the seed from the stalk b. Micropyle – small pore near the hilum c. Raphe – ridge on the seed caused by the bending of seed against the seed stalk 2. Embryo – develops from a fertilized egg (zygote), miniature plant of the seed, consist of: a. cotyledon - seed leaves; they store, digest and absorb food from the endosperm b. epicotyl - part of embryo axis above the point of attachment of cotyledons; contain the meristematic cells which grow into the shoot when the seed spouts (germinates); c. plumule (leaves) - first leaves to develop d. hypocotyl - part of the embryo axis which is below the point of attachment of the cotyledons; the meristematic cells of the hypocotyl develop into the primary root when the seed sprouts; this develops into the stem; the growing tip of the hypocotyl is the radicle e. radicle (root) - lower part of the seed axis which becomes the primary root 3. Endosperm – food-storage tissue that develops from the endosperm nucleus of the embryo sac in the form of starch, protein & oil JSBW’23 5  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT III. SEED GROWTH AND DEVELOPMENT A. Monocot seeds To study the parts of a monocot seed, you can take a close look at a corn kernel. The outermost layer of a corn kernel is the pericarp. If you remove the pericarp, the next layer you’ll find is the endosperm that supplies the embryo with food. Like dicots, monocot embryos have a plumule and a radicle. In monocots, however, the plumule is enclosed in a tubular structure called the coleoptile, and the radicle is enclosed in the coleorrhiza. Monocot embryos have only one thin, leaflike cotyledon. A corn kernel is actually a type of dry fruit called a caryopsis, or grain, that contains a single seed. However, the wall of the fruit, called the pericarp, is fused to the seed coat, so everything inside the kernel is part of the seed. The endosperm provides the growing monocot embryo with energy and building material for growth. Steps of early monocot development: 1. The radicle grows first, piercing the kernel and growing downward into the soil to form the primary root. 2. The primary leaf of the shoot grows upward, pushing its way out of the kernel and the soil. As the leaf grows, it’s protected by the tube-like coleoptile. 3. Once the primary leaf reaches the light, it pushes through the coleoptile and begins to expand. 4. Under the soil, lateral roots begin to develop from the primary root. 5. In corn and some other monocots, adventitious roots called prop roots also develop from the stem and push their way into the soil. B. Dicot seeds Dicot seeds from peas and beans are a little bit different from other dicots because they belong to the group of dicots that uses the cotyledons as food for the embryo. As a result, the cotyledons in these seeds are very large. Most other dicots use endosperm as food for the embryo. In these seeds, the cotyledons are much smaller and look like tiny leaves at the top of the embryo. The bulk of the tissue surrounding the embryo is endosperm. As dicot seeds germinate, the food stored in the cotyledons or endosperm provide the growing embryo with energy and building material for growth. Steps of early dicot development: 1. The radicle begins to grow and emerges from the seed to form the first root, called the primary root. 2. The hypocotyl elongates, pushing its way out of the seed and above the soil. As the hypocotyl emerges from the soil, it’s bent into a curved shape called the hypocotyl arch. The cotyledons protect the upper part of the embryo, called the epicotyl, as it emerges from the soil. 3. Below the soil, secondary roots begin to branch off of the primary root. 4. When the hypocotyl emerges into the light, it straightens out and the epicotyl becomes visible, revealing a pair of true leaves and the apical meristem of the plant. 5. The leaves expand and begin to do photosynthesis In many dicots, including some beans, the cotyledons turn green and also do photosynthesis until they wither and drop off the plant. 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