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Adaptations 1 Adaptations for Protection Evolutionary Changes Over Time • Ice Ages At least five major ice ages have occurred throughout Earth's history: the earliest was over 2 billion years ago, and the most recent one began approximately 3 million years ago and continues today (yes, we live in an ice age!). Currently, we are in a warm interglacial that began about 11,000 years ago. • Continental drift – Mountains, Deserts, New bodies of water • Catastrophic events – Asteroids, Volcanic eruptions • Geographic isolation - “Speciation”: Galapagos Islands • Mutations – Ultra violet light, Chromosomal rearrangement • Natural Hybridizations Humidity Light Water Temperature Wind Environmental Conditions that affect plants Soil Terms – Adaptations for Protection • • • • • • • • • • • • • Dormancy Avoidance strategy Ephemerals Thorns Spines Marginal Spines Prickles Recurved Pilose Pubescent Stinging hairs Cryptic coloration Symbiosis with ants • • • • • • • Callus Leaf abscission Resins Pitch Latex Tannins Alkaloids Protection From the Environment • Dormancy • Ephemerals • Alpine perennials Dormancy • Dormancy is a plants adaptation mechanism to live through periods of time when climatic conditions are too severe to carryout normal plant functions. Avoidance Strategies • Plants that undergo avoidance strategies spend the most severe times of the year climatically in seed form; the main plant dying back. • The main downside of this strategy is a small time window to grow up from that seed to maturity vegetatively, then flower and produce seed as an annual plant. Ephemerals • Ephemerals are plants that wait until climatic conditions are right then produce a small plant, flower and seed all in many cases in 3-4 months. The dormant seeds produced by ephemerals often have to wait for years and are responsible for tremendous desert blooms Gorman, CA Death Valley, CA Goldfields (Lasthenia gracilis) Ephemerals - Annuals This normally bare desert in Namaqualand, Goegap Nature Reserve in South Africa has a proliferation of flowers and desert ephemerals during the brief spring wet season. Protection from Animals OR = Protection from Animals • Thorns, Spines, Prickles – obvious to us • Camouflage – Rare in plants • Symbiosis for Protection – Using Ants as protectors • Wound Healing - Protection from infection • Chemical protection – Tannins and alkaloids. • Other Methods - accumulation of materials from the soil, manufacturing of internal antagonistic particles Thorns, Spines or Prickles In common language the terms are used more or less interchangeably, but in botanical terms, thorns are derived from shoots (so they can be branched or not, they can have leaves or not, and they arise from a bud) spines are derived from leaves (the entire leaf or some part of the leaf that has vascular bundles inside, like the petiole or a stipule Prickles are derived from the epidermis (so they can be found anywhere on the plant, and do not have vascular bundles inside so they can be removed more easily and cleanly than thorns and spines). Thorns vs. Spines Thorn of Pyracantha. B. Spine of barberry (Berberis). The thorn is technically a modified, sharp-pointed stem. It occurs in the axil of a leaf where a branch would normally develop. The spine is technically a modified, sharp-pointed leaf. Since it has a bud in its axil, the spine occurs in the relative position of a leaf. Plants with Thorns Thorns are modified stems Hawthorn and Blackthorn Trees Prunus spinosa Crataegus spp. Thorns of Fouquieria splendens Thorns on Citrus Pyracantha – “Firethorn” Spines Spines - Pereska grandiflora Spines – Modified leaves The Multiple Roles of Cactus Spines Morning dew may be the only form of rainfall for several months in the desert showing another use for spines collecting and directing dew down to the roots. Cephalocereus senilis – Old Man cactus uses hair as camouflage hiding spines beneath and to protect from hot desert sun Marginal Leaf Spines Prickles - Roses Recurved - facing down the stem in order to fend off animals crawling up the stem Prickles – Ceiba speciosa Pilose hair – Leaves Pilose Hair - Stems Pubescent Hairs on Leaves The thick fuzzy covering of hairs on many plants help the plant to conserve water during transpiration keeping the water around the plant longer before being pulled away by the wind or evaporated off too quickly by the sun Stachys byzantina – Lambs ears Stinging Hairs on Stinging Nettle The miserable sting felt from the many hollow stinging hairs called trichomes on the leaves and stems, which act like hypodermic needles, injecting histamine and other chemicals that produce a stinging sensation when contacted by humans and other animals Stinging nettles are also attributed with helping with the symptoms of some forms of arthritis, some allergies, urinary tract infections, and hair and skin conditions as well as bring a digestive aid Camouflage – Lythops “Living Stones” Cryptic (hidden from view) Coloration Only the tops of the fleshy leaves of the Lythops protrude above the soil line where it acts like a window focusing the light further down chloroplasts deep below. It is thought to protect the plant from animals seeking succulent leaves for moisture in the rocky deserts of South Africa Symbiosis With Ants https://www.youtube.com/watch?v=IkTs0Q3JUls 2 species of acacia have developed a symbiotic relationship with and colonies offering both a nutrient source and housing in exchange for a rapid response “all hands on deck” defense from browsing herbivores like elephants. Acacia sphaerocephala Bull horn acacia Whistling Thorn Acacia Acacia drepanolobium Another species of acacia tree that provides shelter and food in exchange for immediate defense of the tree Wound Healing • • • • • • • • Tannin Callus Resin Gums Wound wood Latex Branch Collar Branch bark Ridge Callus Callus is a material (polysaccharide molecule) laid down at the wound sites of many plants to resist the invasion of pathogens. It also precedes the process of wound wood production in woody trees. Callus – Wound wood Woundwood is a specialized wood laid down by woody plants and trees to close off and compartmentalize damaged areas of wood tissue and protect it from disease and pathogen. Woody plants don’t “Heal wounds but merely close them off and protect all new wood being formed. A properly healing wound – First immediately covered with Callus to corm a infection barrier and then healing over the wound with wound wood Knots in lumber are areas of old broken or cut branches closed off inside the wood. Woundwood - 3 years Year 1 Year 2 Year 3 Good tree pruning works with the trees natural wound repair system When removing a branch the rule is to make the removal cut just outside the Branch Collar to allow the tree full access to it’s natural repair processes of callus and wound wood Wound wood Leaf Abscission Leaf scar with visible vascular bundles The Development of a Leaf Abscission Layer Resins Plants secrete resins and rosins for their protective benefits. They confound a wide range of herbivores, insects, and pathogens; while the volatile phenolic compounds may attract benefactors such as parasitoids or predators of the herbivores that attack the plant. The resin produced by most plants is a viscous liquid, composed mainly of terpenes, with lesser components of dissolved nonvolatile solids, which make resin thick and sticky. Wikipedia Resin/Pitch Trees often respond to invasion of their bark layer by flooding the hole with pitch pushing out the invader and plugging the hole. The response is normally almost immediate but when the tree is stressed the response time can be delayed allowing more successful invasions Latex - Ficus Most Ficus in the Moraceae family produce a white latex that seals wounds and acts as an antibacterial, fungicidal and even an anti herbivore material. Some people have latex allergies and must avoid exposing their skin to Ficus latex Latex - Euphorbia Euphorbia like the Fig Family Moraceae produces a white latex that protects wounds from infection. The latex from Euphorbia (depending on the species) can be problematic when coming in contact with the skin or especially the eyes of humans. The latex of the poinsettia which is a Euphorbia as well has little to non of this effect Tannins Tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids. The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather; hence the words "tan" and "tanning" for the treatment of leather The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation, and perhaps also as pesticides, and in plant growth regulation. The asstringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine. Likewise, the destruction or modification of tannins with time plays an important role in the ripening of fruit and the aging of wine. Wikipedia Gums Gums are slightly different than resins in their chemical composition, but like resins dry on exposure to air and form a protective barrier to wounded tissues Cherry tree gum The Chicle tree is responsible for chewing gum manufacturing Manilkara chicle Alkaloids Rhubarb leaves contain a high concentration of Oxalic acid which can make you sick if you consume large quanities The prized sugary stem of the rhubarb is the part we often eat Alkaloids • Extracts from plant alkaloids have played a large role in pharmaceuticals: pain relievers, cardiac and repertory stimulates, muscle relaxants, blood vessel constrictors, cures for malaria, and pupal dilators used in eye exams. • Caffeine, nicotine, morphine, extracted from plant products have addictive qualities • Phytotoxins: Hemlock, Castor bean, Solanine Chemical Protection - Secondary Products • There are several chemicals produced by plants that don’t help serve the primary functions of the plant (Growth, Respiration, Reproduction etc.) but fulfill a secondary roll often unknown by us. Some of these chemicals (Secondary Products) we have learned do serve a purpose to the plant and we as humans have also benefitted greatly from some of these organic compounds in our daily lives. Protective Chemical Review • Tannin – astringent taste (unripe fruit) bind with proteins causing cellular death • Resin – non water soluble, conifers, hardens in air • Callus – Parenchyma cell rapid protective layer over wounds • Callous – Not to be confused with Callus this material is used by the plant to plug damaged phloem tubes • Latex – White bleeding, dries to protective coat • Gums – water soluble, dry to a protective coat • Alkaloids – one of the most diverse and heavily studied of plant secondary compounds providing many medicinal uses for us Solanaceae - The Nightshade Family Contains: The Potato S. tuberosum TheTomato S. lycopersicum The Eggplant S. melongena Chile peppers Bell Peppers Fruits/tubers of these plants highly prized but the leaves contain Alkalloids that can be poisonous if consumed