Plant Morphology - Stems - Lecture Notes PDF

Module 6: Plant Morphology STEMS Ainsley C. Medina, RPh, PharmD  STEMS Considered as an aerial part of the plant; The axis of the shoot system which provides mechanical support to the plant; The site where leaves and reproductive shoots get attach...

Module 6: Plant Morphology STEMS Ainsley C. Medina, RPh, PharmD  STEMS Considered as an aerial part of the plant; The axis of the shoot system which provides mechanical support to the plant; The site where leaves and reproductive shoots get attached; Exposes the leaves for ___________ and positions the reproductive shoots for optimal access to pollinators and dispersal agents.  STEMS Main functions in plants: 1 Support 3 Growth 2 Conduction Xylem & Phloem 4 Storage Succulents  Stems may either be: Herbaceous consisting of thin, soft, nonwoody tissues with extensive hard Woody tissues of wood and bark; taller, thicker  Bud scale Terminal bud Tip of a stem Outer protective layer which covers the terminal bud Terminal bud scale Marks leaves on stem scars serving as external Node measure of annual Segment of stem growth where leaves & lateral buds are attached Axillary bud/ Leaf scar Occurs in the leaf axis Internode on the side of a stem Section of a stem between two nodes Lenticels Pores that allow gas exchange Bundle scars Used for identifying woody plants; mark left in the leaf scar External parts from vascular tissue attachment  Dicot stem Monocot stem Epidermis Trichomes Present Absent Cuticle Present Present Hypodermis Made up of Made up of Internal collenchyma sclerenchyma parts Vascular bundle Arranged in one/ Scattered across arrangement two broken rings the stem with any with a definite definite shape arrangement Bundle sheath Absent Present Cortex & Stele Present Absent Internal parts Composed of dividing cells responsible for the initiation of new leaves and buds and for making the three primary meristems – protoderm, procambium, and ground meristem. shoot apical meristem (SAM) Protected by bud scales of the bud by leaf primordia – tiny embryonic leaves that will develop into mature leaves after the bud scales drop off and growth begins shoot apical meristem (SAM)  Growth 1.1 1 Protoderm Epidermis 2.1 2 Procambium Primary Xylem & Phloem 3.1 3 Ground meristem Pith & Cortex  Growth Primary vs Secondary  Growth Primary result of increase in rapidly- stem dividing cells thickness in the apical meristems at the shoot tip vs due to the activity of the lateral and root tip; subsequent Secondary meristems which lacks elongation in __________  Vascular cambium Its cells divide and produce two complex tissues: secondary xylem (_________)– to replace the primary xylem, and secondary phloem (____________)– to replace the primary phloem. Why the primary ones are replaced by the secondary?  Cork cambium “___________”, divided to produce cork cells, containing a waxy substance known as suberin that can repel water, and cork parenchyma (____________).  Cork cambium The tissues it does produces are called periderm where it functions as a replacement for the epidermis, which splits apart as the stem increases in girth. Remember… Monocot & Dicot stems are usually found in herbaceous stems. Vascular & cork cambiums are developed in woody plants. Vascular cambium First becomes active in spring Spring wood Becomes small, after spring Summer wood Results in alternating concentric rings of light and dark **Annual ring - cells over a one year period of years growth … Results in alternating concentric rings of light and dark cells over a period of years Vascular rays Does consist of parenchyma cells, and is responsible for conducting nutrients and water and storing food. **Any part of a ray within the xylem is called a xylem ray, while its extension through the phloem is called a phloem ray.  STEM MODIFICATIONS Thickened underground Rhizomes stem that has distinct nodes and internodes and scaly leaves Grows parallel to the ground and has a creeping stem with long internodes; Runners develops from the axils of lower leaves of aerial stem  STEM MODIFICATIONS Produced beneath the Stolons surface of the ground (like the runners) and tend to grow in different directions but not horizontally Slender twining strands enabling plant to seek support Stem while climbing other surfaces tendrils  STEM MODIFICATIONS Short, vertical, swollen Corms underground stem serving as a food storage organ enabling plant to survive “Phyllocades”, green, flattened, and cylindrical stem resembling a leaf; capable of Cladophylls performing photosynthesis  STEM MODIFICATIONS Rhizome’s thickened end Tubers that is fleshy and enlarged for food storage Tunicate Modified Does have a papery outer covering underground bud which protects from digging/ drying out attached to a short stem; Bulbs covered by paper- Does not have; Non- susceptible to like bulb scales– damage tunicate modified leaves  Pharmaceutical & Pharmacological Importance Button Snakeroot Camphor Eryngium aquaticum spp Cinnamomum camphora Inserted chewed Oil from leaves & stem in nostrils wood used in cold to arrest epistaxis remedies & liniments  Pharmaceutical & Pharmacological Importance Cascara Cat’s claw Rhamnus purshiana Uncaria tamentosa Used in intestinal Bark extract problems like widely used as diverticulosis & Chron’s laxative disease; lowers BP (thru Hirsutin); inhibits platelet clotting, increases serotonin  Pharmaceutical & Pharmacological Importance Cherry Chinese Magnolia Prunus serotina Magnolia officinalis Used for coughs For nasal stuffiness & & colds discharge; alleviates asthma & sinus headache  Pharmaceutical & Pharmacological Importance Chinese rubber tree Cinquefoil Eucommia ulmoides Potentilla erecta Improves circulation Dried rhizome used to hands & feet; to control diarrhea reduce BP; alleviate frequent urination  Pharmaceutical & Pharmacological Importance Cotton Ephedra Gossypium hirsutum/ E. nevadensis/ E. sinica barbadanse Induces abortion “Ma-huang”; for nasal congestion and BP lowering; contains toxic amounts of cyanide  Pharmaceutical & Pharmacological Importance European birch Fennel Betual pendula Foeniculum vulgare Used for kidney Used as an appetite stones & UTI suppressant and eyewash  Pharmaceutical & Pharmacological Importance Lilly of the valley Cinchona Convallaria majalis Cinchona pubescens Controls irregular Practical source of heart beat; however, Quinine used for is poisonous malaria  End Thank you! 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