Plant adaptations Video on plant adaptations What kind of stressors do plants have? Environmental stressors can be abiotic (from ____________ sources) or biotic (from __________ sources) Drought, ______________, cold, low light, and poor nutrient availability are abiotic stressors ______________ and pathogens are biotic stressors Examples of plant adaptions to abiotic stressors 1) Low nutrient availability some plants live in areas where the amount of nutrients in the soil is low (eg. bogs). In order to obtain more nutrients they become ________________ (i.e. eat small animals such as ___________) eg: The ______________ plant, _________________ “...The slippery sides of each pitcher are lined with downwardpointing 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 fleshdissolving enzyme. The decomposed bodies of the insects provide essential nutrients for the pitcher plant.” Bill Casselman, Common Garden Words, Macarthur and Company, 1997 2) Living in water Excess water leads to __________ deprivation The ___________ roots of mangroves, called pneumatophores, provide access to oxygen. floating leaves that have stomata on the ________ surface for gas exchange (eg. water lily). venus fly nonliving trap carnivorous insects aerial oxygen Herbivores pitcher living flooding upper 1 3) Drought When water is scarce or only seasonally available, plants need to transpire but at the same time minimize __________ loss. Mechanisms to reduce transpiration rate during dry spells Control of the ____________ (opening and closing) Inhibition of growth of young leaves Leaves that roll or fold Loss of leaves by _______________ trees in the autumn ____________shaped leaves of ___________ 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 ______________ are Plants Adapted to Dry Environments Mechanisms to reduce water loss while transpiring in xerophytes: Waxy cuticles, sunken stomata on the lower epidermis Photosynthetic stems that store water; leaves that are spines (eg _________) Leaves of xerophytes may also have an abundance of fibers to provide support when turgour (water) pressure is low Leaves that fold Oxalis Needlelike leaves spruce stomata deciduous needle Xerophyte cactus cacti conifers xerophytes water 2 Examples of plant adaptions to biotic stressors 1) Predation by herbivores 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 (actively growing cells) at the _______ of the leaf. Grow from the bottom up Spines (modified leaves), _________ (modified stems), and prickles (epidemal outgrowths) are mechanical deterrents to predators Many plants produce secondary compounds that are poisonous or bitter tasting to animals – often the source of our drugs ____________ from tobacco (Nicotiana sp.) ________________ from coffee (Coffea arabica) Morphine, codeine, and heroin from ___________ (Papavar sp.) Strychnine (rodent poisoning) from the tropical vine Strychnos toxifera tobacco plant chemical defence cow eating grass Hawthorn bush mechanical defence thorns base nicotine caffein poppies 3
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