BOT3015 - Adaptations: Environments and Light

Floristic Kingdoms

Taxonomic groupings that reflect geological and evolutionary history

Holarctic

Most of North America and temperate Laurasia

South American

From South Florida to Patagonia

African

All of Africa except the Mediterranean area

Indo-Pacific

From India to Pacific Island

Australian

Australia and some surrounding islands

Tundra

Small-sized plants adapted to short seasons

Taiga

Conifer Forests

Deciduous Forests

Broad-leaf temperate forests

Grasslands

Prairies, Steppes, Savannah, Pampas

Shrublands

Chaparral, Scrub, etc.

Desert

Plants are further apart than in

shrublands, little water

Tropical Forests

Humid and warm with peak diversity

Environmental Factors

Things outside the system that can impact the operation of the system

Biotic factors

Resulting from interactions with other organisms such as : herbivory, infection, symbiosis, competition

Abiotic Factors

Nonliving components of environment. Includes parameters

(temperature, pH, humidity) and resources (light, water, minerals) that determine growth - as well as others that can add stress (e.g. pollutants)

Limiting Factors

One environmental factor at suboptimal level can limit plant

processes. ex.) At a given light intensity level photosynthetic rate can be limited by level of CO2

Stress

Occurs when essential factors (such as light, water, oxygen, nutrients) are at inappropriate levels (higher OR lower)

Environmental Noxa

Factors that trigger stress at ANY concentration

(e.g. heavy metals, pollutants, etc)

State of Latent Life

Minimal life processes occur when stress factors are too high/low

Dormancy

an adapted latent life stage - triggered by environmental cues. Involves physiological changes (e.g. abscession of

leaves, production of bud scales, etc).

Avoidance Strategy

Seeds and spores allow annual/ephemeral plants to avoid moments of highest environmental stress.

Mesophiles

Plants that require moderate temperatures to grow.

Hardening

The process by which tolerable stress levels trigger the plant to prepare for extreme conditions.

Leaf Changes - Surface

Hairs can reduce evaporation and reflect intense sunlight

Leaf Changes - Size

Smaller, thicker leaves help minimize effect of high light intensity

Leaf Changes - Angle/Position

Some species (e.g. legumes) can move leaves to reduce

exposure to sunlight.

Transpiration

increased transpiration can help maintain the plant cooler than surrounding environment

Shading

Plants use some structures to protect others from direct sunlight

Avoidance Strategy - Temperature

In hot environments, many species are short-lived annuals

(ephemeral) - avoiding worst conditions

Rosette/Low growing plants

Protected against weight of snow & environment

warmer close to ground

Evergreen Plants

High concentrations of sugar in leaves act as anti-freeze

Deciduous Plants

Leaf abscission and bud scales to protect axillary

meristems

Photosynthesis

A process that requires carbon dioxide and water as reactants and produces sugars and oxygen.

Chlorophyll

A green pigment found in the chloroplasts of plants, algae, and some bacteria

Thylakoid

A flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy.

Sunlight

(via photosynthesis) produces the vast

majority of energy for life on Earth.

Light - Too Low

Negative energy balance - not enough photosynthesis to cover plant's metabolic requirements

Light - Too High

Unused energy can lead to oxidative stress.

Pulvini

Joint-like thickening at base of leaves (e.g. legumes) that allows for movement of leaves.

Chloroplasts

Capture energy from sunlight and use it to produce food for the cell. They will move to different parts of the cell

to increase or reduce exposure to light!

Sun Leaves

Smaller and thicker, with well- developed mesophylls and several layers of palisade cells - epidermal hairs might

minimize excess sunlight.

Shade Leaves

Larger and more tender, with weakly develop mesophylls - epidermal cells might act as lenses to increase light capture!

Sun Leaves - Subcellular Level

Chloroplast with small grana and few stromal thylakoids (A)

Photosystem (Sun Leaves)

Small proportion of antenna and many reaction centers

Shade Leaves - Subcellular Level

Chloroplast with large grana and many stromal thylakoids (B)

Photosystem (Shade Leaves)

Large proportion of antenna and few reaction centers

Stolons

Aboveground stems; emerge from crown and bend downwards; develop plantets where they touch the ground

Stoloniferous Rhizomes

Belowground stems; upright shoots develop from axillary buds in nodes; adventitious roots in underside

Suckers

Upright shoots growing from horizontal roots (aka "adventitious shoots")

Twiners

Stems of vines that grow in spirals around objects such as small trunks. These stems support themselves

Tendrils

Modified leaf or short stem that wraps around objects they touch. These leaves/stems provide support for main stem

Adhesive Pads

At the tips of tendril-like short stems. These pads allow plants to attach to walls

Supportive Roots

Roots that plants form in soft wet soils to help them grow taller

Buttress Roots

Roots that are wedge-shaped, tall and wide - they prevent shallow-rooted trees from falling over

Prop Roots

Advetitious/aerial roots that arise from the trunk (or large branches) and grow downwards to provide support in

shifty conditions (e.g. mangroves)

Epiphytes

Plants that grow in wet areas. They use their roots to grasp tree branches (instead of water absorption)

Lianas

Typically in rainforests; woody, creeping vines that spread through the canopy spreading their leaves to the sun.

Raunkiaer

Scientist that proposed a sequence of life forms based on how they deal with protecting their meristem.