Crop Science Notes PDF

CROP SCIENCE RUSSEL VAN R. ROA MSc Horticulture (candidate), UP Los Baños BSA Horticulture, Central Mindanao University Nature and Composition of Plants CONTENTS: 1. Overview of Plant Structure 2. Plant Cells 3. Plant Tissue and Tissue Systems 4. Major Plant Organs Nature and Composition of...

CROP SCIENCE RUSSEL VAN R. ROA MSc Horticulture (candidate), UP Los Baños BSA Horticulture, Central Mindanao University Nature and Composition of Plants CONTENTS: 1. Overview of Plant Structure 2. Plant Cells 3. Plant Tissue and Tissue Systems 4. Major Plant Organs Nature and Composition of Plants General Overview of Plant Structure All plants have similar body plan despite immense diversity Composed of 3 major organs: a. Stem – supports the aboveground parts b. Roots – anchorage; for water and nutrient absorption c. Leaves – gas exchange; transpiration and photosynthesis Roots and shoots grow vertically; leaves grow laterally. Leaves’ lateral exposure captures light. Stem elongate upward to elevate the leaves to capture sunlight. Roots elongate downwards to search for nutrients and water. Nature and Composition of Plants THE PLANT CELLS Consists of the: a. Apoplast – the cell wall b. Protoplast – “living component”” of the cell that includes the plasma membrane and the organelles Nature and Composition of Plants Cell Walls Imparts stability and rigidity to Heldt, H.W. et al. 2010. Plant Biochemistry. Academic Press. Elsevier. Cellulose the cells Made up of cellulose, hemicellulose, pectins & expansins Cell walls are cemented together Hemicellulose by middle lamella There are two types of cell walls: Primary walls – thin; growing cells. Secondary walls – thick due to lignin Pectins Nature and Composition of Plants Plasmodesmata Enables exchange of developmental signals through proteins, nucleic acids and other macromolecules. Intercellular transport through plasmodesmata is called symplastic transport. Transport through the wall spaces or apoplast is called apoplastic transport. Heldt, H.W. et al. 2010. Plant Biochemistry. Academic Press. Elsevier. Nature and Composition of Plants Plasma membrane Outer fluid boundary of the living cytoplasm Selective barrier that allows the entry of oxygen, nutrients and waste to service the entire cells. Consists of phospholipid bilayer. Taiz, L. et al. 2015. Plant Physiology and Development 6th Ed. Sinauer Associates, Inc. USA. Nature and Composition of Plants Cytoplasm A term describing the organelles suspended in the cytosol. Cytosol – semi-fluid substance filling the interior of the cell and embedding the other organelles and subcellular compartments Heldt, H.W. et al. 2010. Plant Biochemistry. Academic Press. Elsevier. Nature and Composition of Plants Endoplasmic Reticulum Major source of membrane phospholipids, membrane proteins and act as protein cargo. Smooth ER – performs lipid synthesis (oil, steroids and new membrane phospholipids); for drug and poison detoxification; stores calcium ions. Rough ER – has ribosomes which perform protein synthesis; membrane factory by incorporating membrane proteins and lipids on its own membrane. https://microbenotes.com/rough-vs-smooth-endoplasmic-reticulum/ Nature and Composition of Plants Ribosomes Protein factories that consist rRNA and proteins. Free ribosomes – suspended in the cytosol. Bound ribosomes – attached to the ER or on the nuclear envelope. Taiz, L. et al. 2015. Plant Physiology and Development 6th Ed. Sinauer Associates, Inc. USA. Nature and Composition of Plants Vacuoles Occupies 95% of the cell volume surrounded by a membrane (tonoplast). Increase in volume of cells is primarily due to enlargement of vacuole. Maintain cell turgor by accumulation of salts from organic and inorganic acids Lytic vacuoles – degrades macromolecules into simpler forms to be used by the cells. Taiz, L. et al. 2015. Plant Physiology and Development 6th Ed. Sinauer Associates, Inc. USA. Nature and Composition of Plants Mitochondria Site of cellular respiration that uses oxygen to produce ATP from sugars, fats, and other fuel sources. “Powerhouse of the cells” Taiz, L. et al. 2015. Plant Physiology and Development 6th Ed. Sinauer Associates, Inc. USA. Nature and Composition of Plants Plastids Cell organelles which only occur in plant cells. Descended from proplastids in the egg cells which becomes: Chloroplast – contains chlorophyll and appears green; site of photosynthesis. Chromoplast – high in carotenoid pigments which appears red, orange and yellow. Leucoplast ✓ Amyloplast - stores starch in non-green tissues such as roots, tubers and seeds ✓ Elaioplast – storage of fatty acids, terpenes and other lipids. ✓ Proteinoplast – contains crystalline bodies of proteins Taiz, L. et al. 2015. Plant Physiology and Development 6th Ed. Sinauer Associates, Inc. USA. Nature and Composition of Plants Plastids Cell organelles which only occur in plant cells. Descended from proplastids in the egg cells which becomes: Chloroplast – contains chlorophyll and appears green; site of photosynthesis. Chromoplast – high in carotenoid pigments which appears red, orange and yellow. Leucoplast – non-pigmented ✓ Amyloplast - stores starch in non-green tissues such as roots, tubers and seeds ✓ Elaioplast – storage of fatty acids, terpenes and other lipids. ✓ Proteinoplast – contains crystalline bodies of proteins https://en.wikipedia.org/wiki/Plastid Nature and Composition of Plants Golgi Apparatus It is where the proteins are processed and sorted out for transport to other organelles. Modification and packaging of the proteins produced by ribosomes. Heldt, H.W. et al. 2010. Plant Biochemistry. Academic Press. Elsevier. Nature and Composition of Plants Nucleus Contains the genetic material which codes for proteins for cellular metabolism, growth and differentiation. Enclosed in a nuclear envelope. Nucleolus – site of ribosomal RNA (rRNA) synthesis out from the genes in the DNA. Nature and Composition of Plants PLANT TISSUE AND TISSUE SYSTEMS 1. Meristematic Tissues 2. Dermal Tissues 3. Ground Tissues 4. Vascular Tissues Nature and Composition of Plants Meristematic Tissues Areas where cells are actively dividing or where nuclear division Apical Meristem – primary growth (mitosis) and cell division (cytokinesis) is highly concentrated. Intercalary Meristem Nature and Composition of Plants Meristematic Tissues Lateral Meristem – secondary growth Nature and Composition of Plants Dermal Tissue Outer protective layer of the plant composed of: Epidermis – mechanical protection; reduce water loss due to cuticle; aerates internal tissues via stomata. Periderm – protective tissues in the roots and stems in the absence of epidermis; aerates internal tissues via lenticels. Nature and Composition of Plants Ground Tissues Fills out the three-dimensional bulk of the plant. Parenchyma – have thin and flexible primary walls; storage site for starches, proteins, oils, etc. Collenchyma – elongated cells with thick walls; provide support to elongated stems. Sclerenchyma – have thickened lignified walls; provides permanent support; aids in conduction of water as in the xylem. Sclerenchyma cells Nature and Composition of Plants Vascular Tissues Xylem – delivers water and nutrient Phloem – translocates photosynthetic upward from the roots into the products from the leaves to the storage shoots. organs and actively dividing cells Nature and Composition of Plants Plant Organs: 1. Roots 2. Stems 3. Leaves 4. Flowers 5. Seeds Nature and Composition of Plants Roots Anchors plants into the soil; absorbs water and soil minerals Stores carbohydrates and other food reserves (root crops). Primary root – first to emerge after germination (radicle). Secondary root – arise from primary root which increases water and nutrient acquisition. Taproot system – has one main vertical root which enhance plant anchorage; makes the plants grow taller. Fibrous system – found among monocots; has a thick mat of slender roots; Nature and Composition of Plants Stems Bears the leaves and buds derive from epicotyl of seedlings. Consists of alternating nodes where the lateral shoots arise. Raises the leaves and flowers to enhance sunlight exposure and facilitate pollination, respectively.  Nature and Composition of Plants Stems Modifications Rhizomes Suckers Tubers Stolons/runners Bulb corm Nature and Composition of Plants Leaves Consist of a flattened blade (lamina) and petiole --- attaches itself to the nodes. Site of photosynthesis, gas exchange, and transpiration (for heat dissipation). Some leaves have important physical and chemical attributes to prevent herbivory by animals. Stomatal opening and closing Nature and Composition of Plants Economically useful parts Leaf sheath in Abaca Spathe Terminal buds Spathe Spadix Leafy vegetables Bracts  Flowers Nature and Organ for reproduction in most angiosperms Composition of Accessory parts: ▪ Petals (corolla) – highly colored used to Plants attract pollinators ▪ Sepals (calyx) – green leaf structure which encloses the bud at early stage. ▪ Receptacle – enlarged base of a flower where floral organs are arranged. Essential parts ▪ Pistil (gynoecium) – female ❑ Ovary – contains ovules > seeds ❑ Stigma – pollen landing site ❑ Style – connects the ovary and stigma ▪ Stamen (androecium) – male ❑ Anther – contains the pollen ❑ Filament – stalk of the anther Nature and Composition of Plants Classification of Flowers Complete – have all the parts Monoecious – both male and female parts are Incomplete – lacks one of the parts found in one plant Dioecious – male and female parts are found in different plants of the same species Perfect – has pistil and stamen Imperfect – either pistil or stamen is present Dioecious Staminate – stamen only Pistillate – pistil only Female papaya Male papaya Nature and Composition of Plants Fruits Mature, ripened ovary resulting from fertilization of the egg cell. Parthenocarpy – fruit development without fertilization like banana, pineapple, and seedless grapes. Consists of three layers: Exocarp – outer covering which is colored, thick and has oil glands beneath the surface. Mesocarp – middle part that is often fleshy (mangoes) or fibrous (coconut). Endocarp – boundary around the seed and maybe hard and stony or papery. Nature and Composition of Plants Parthenocarpy in Fruits Parthenocarpy – fruit development without fertilization like in banana, pineapple, and seedless grapes. Application of hormones like auxin, gibberellins and cytokinin induces parthenocarpy. Parthenocarpy is important in citrus for fresh consumption. Parthenocarpy happens naturally through: Lack of pollination Pollination but with no fertilization After fertilization, the embryo is aborted. Nature and Composition of Plants General Classification of Fruits Nature and Composition of Plants Classification Fruits 1. Simple Fruits – formed from single pistil Dry Fruits a. Dehiscent Fleshy Fruits i. Legume a. Drupe ii. Follicle iii. Capsule b. Berry b. Indehiscent i. Pepo i. Achene ii. Hesperidium ii. Nut c. Pome iii. Grain/caryopsis iv. Samara v. Schizocarp Nature and Composition of Plants Fleshy Fruits ▪ One seeded fruit arising from superior ovary Drupe ▪ Exocarp is relatively thin ▪ Mesocarp is either fleshy or fibrous ▪ Endocarp is stony or hard Berry ▪ Exocarp is thin and distinct ▪ Mesocarp and endocarp are fused, enlarged and juicy Hesperidium ▪ Exocarp or rind is leathery ▪ Fruit is divided by septa which indicates the number of carpels the fruits have Nature and Composition of Plants Fleshy Fruits ▪ Exocarp or rind is thick and hard at maturity Pepo ▪ Has fused endocarp and mesocarp not divided by septa. Pome ▪ Accessory fleshy fruit formed by a group of carpels firmly united with each other and surrounded by and united to the floral tube or receptacle. Nature and Composition of Plants Dry Fruits - Dehiscent ▪ Developed from 1 carpel which splits along Legume both the ventral and dorsal sutures at maturity Follicle ▪ Developed from 1 carpel which splits along only 1 suture Capsule ▪ Developed from several carpels ▪ It has many types such as: loculicidal, septicidal, silique, silicle, pyxis, poricidal Nature and Composition of Plants Dry Fruits – Indehiscent ▪ One seed is attached to the fruit wall at a single point (sunflower) Achene ▪ Similar to achene but with the fruit wall greatly hardened and thickened Nut ▪ Similar to achene although the fruit wall and Grain/caryopsis the seed coat are fused Nature and Composition of Plants Dry Fruits – Indehiscent Achene Nature and Composition of Plants Dry Fruits – Indehiscent ▪ One- to two-seeded fruit in which part of the Samara fruit wall grows out into a wing ▪ Fruits formed from several carpels and each carpel of the pistil encloses a single ovule at maturity Schizocarp ▪ The carpels separate as separate indehiscent fruits Nature and Composition of Plants Fruits 2. Aggregate Fruits – fruit formed by the 3. Multiple Fruits – derived from many flowers development of a number of pistil from which are usually clustered such as in the same flower such as in strawberry pineapple, rimas, jackfruit Nature and Composition of Plants Seeds ▪ Ripened ovule consisting of embryo and stored food supply enclosed in a seed coat ▪ Dicotyledon – embryo lies within the axis of 2 cotyledons ▪ Monocotyledon – consist of seed coat, endosperm and emryo Nature and Composition of Plants Part of the Seed ▪ Embryo – rudimentary plant inside the seed ▪ Seed coat – outer protective layer ▪ Endosperm – food reserves ▪ Hilum – scar on the seed coat where it was attached to the ovary wall. ▪ Micropyle – seed pores ▪ Radicle – future root system ▪ Plumule – future shoot system ▪ Hypocotyl – part just above the roots and below the cotyledonary stalk Hilum? Nature and Composition of Plants Types of Seeds ▪ Dries out naturally in the plant at (