Environmental Adaptations of Plants

1. Environmental Adaptations of Plants Topic 14.5 Biology 1001 November 30, 2005

2. Introduction • Seed & pollen dispersal means that plants occupy numerous environments • Plants have developed evolutionary adaptations to many environments • These include morphological, physiological, anatomical & reproductive modifications • Environmental stressors can be biotic or abiotic, periodic or continuous • Drought, flooding, cold, low light, and poor nutrient availability are abiotic stressors • Herbivores and pathogens are biotic stressors

3. Newfoundland’s Environment • Dwarf black spruce (Picea mariana) or “tuckamore” is an adaptation to a cold, windy coastal environment • Influences the pattern of growth and form or morphology of the plant Lise Sorensen

4. Newfoundland’s Environment • Pitcher plant (Sarraceniapurpurea) • Adapted to low nutrient availability in peatland bogs “Sarracenia purpurea (Botanical Latin, purple, referring to the colour of the mottled pitchers) is the floral emblem of Newfoundland and Labrador. Our pitcher plant is the stout little carnivore of Canada’s peat-quilted swamps and jelly-earthed bogs, where it traps insects in leaves modified to hold water, hence pitcher plant. The slippery sides of each pitcher are lined with downward-pointing hairs that help insects slide into the pitcher but prevent them from escaping. Trapped without mercy, they struggle, fall exhausted back into the water, and drown in the liquid to which the plant has added a flesh-dissolving enzyme. The decomposed bodies of the insects provide essential nutrients for the pitcher plant.”- Bill Casselman, Common Garden Words, Macarthur and Company, 1997

5. PLANT Adaptations to Drought • When water is scarce or only seasonally available, plants need to transpire but at the same time minimize water loss Adaptations of Plants That Endure Dry Periods • Mechanisms to reduce transpiration rate during dry spells - Control of stomatal opening and closing* - Inhibition of growth of young leaves - Leaves that roll or fold (- Loss of leaves by deciduous trees in the autumn - Needle-shaped leaves of conifers) • Such mechanisms are a compromise because they also reduce photosynthesis • Roots also respond to dry periods - Shallow root growth is inhibited - Deep roots continue to grow to where the soil is still moist * See Topic 14.34 Notes and Text Reading () Loss of water due to freezing

6. Leaves that fold - Oxalis Leaves that roll – Ammophila arenaria

7. Xerophytes are Plants Adapted to Arid Environments * See Topic 14.34 Text Reading • Mechanisms to reduce water loss while transpiring • Waxy cuticles, sunken stomata on the lower epidermis, trichomes (hairs) • Photosynthetic stems that store water; leaves that are spines • Leaves of xerophytes may also have an abundance of fibers to provide support when turgour pressure is low Nerium oleander Fig. 36.16

8. Xerophyte Adaptations That Reduce Transpiration • Crassulacean acid metabolismof succulents in the family Crassulaceae and ice plants • Stomata stay closed during the day, open at night to take in CO2 • Store CO2 as malic acid (organic acid) in vacuoles • Malic acid is broken down during the day to provide CO2 Crassula portulaceae 'Hobbit' - Baby Jade Ice Plant Carpobrotus edulis

9. ADAptations to life in water • Excess water leads to oxygen deprivation • The aerial roots of mangroves, called pneumatophores, provide access to oxygen • Oxygen deprivation in other plants stimulates the production of the hormone ethylene, which causes some of the cells in the root cortex to undergo apoptosis, or programmed cell death

10. Hydrophytesare Plants Adapted to An Aquatic Environment • Such plants are secondarily aquatic – their ancestors evolved on land • Adaptations include leaf heterophyly (floating and submerged leaves have different forms) and stomata on the upper surface of the leaf

11. Reproductive Adaptations to Cold • Sun-tracking flowers • Hairy flowers that absorb IR radiation • Higher rates of asexual reproduction – stolons, rhizomes, bulbs on flowering stalks Salix Allium canadense

12. PREDATION BY HERBIVORES • Predation is important in chemical recycling because it returns nutrients to the soil • Plant defenses to predation include developmental, mechanical and chemical modifications • Grasses are supremely adapted to grazing, continuing to grow throughout the season due to a meristem at the base of the leaf • Spines (modified leaves), thorns (modified stems), and prickles (epidemal outgrowths) are mechanical deterrents to predators

13. Chemical Defense Against Predation • Many plants produce secondary compounds that are poisonous or bitter tasting to animals – often the source of our drugs Nicotine from tobacco (Nicotiana sp.) Caffeine from coffee (Coffea arabica) Morphine, codeine, and heroin from poppies (Papavar sp.) Strychnine from the tropical vine Strychnos toxifera Jackbeans produce canavanine, which replaces arginine in the proteins of the herbivore

14. Coffea & Nicotiana?