Biology 633 Environmental Plant Physiology Study of how the environment affects the function of plants Alpine tundra Desert Tropical rainforest aderfasi@yahoo.com

Module overview Discuss interplay between the genetic potential of plants and environments in which they grow Impact of short-term changes in the environment on physiology, morphology and growth of plants Stress response, acclimation and adaptation of plants in response to changes in environment 16 lectures and 4 practical sessions

Overview of lectures Introduction to Environmental Plant Physiology Response of plants to their environment Plant growth analysis Photosynthesis; mostly C3 plants C4 and CAM plants Respiration Water, drought and plant growth Adaptation of plants to growth on the sea floor

Recommended texts Lambers, Chapin & Pons (1998) Plant Physiological Ecology Atwell, Kreidemann & Turnbull (1999) Plants in Action Fitter & Hay (1987) Environmental Physiology of Plants Larcher (1995) Physiological Plant Ecology Taiz & Zeiger (1991) Plant Physiology

Lecture 1 Learning objectives Define Physiological Ecology Appreciate dynamic nature of the plant/environment interaction Be familiar with variations in environmental conditions between and within habitats Importance of time scales in determining response of plants to their environment

Plants: static or dynamic?

Visually stunning

Their structures respond to changes in environment (e.g. shade)

Their metabolism is constantly changing response to large variations in environment

Temporal variation in temperature

…….and light intensity

Global environment is also changing e.g. greenhouse gases, temperature, nutrients, UV-radiation

Rising atmospheric CO2 concentrations Atmospheric CO2 concentration (ppm) Year

…….enormous flow of CO2 in and out of leaves

…….and these are cells that remove CO2 from the atmosphere

What is Environmental Plant Physiology (EPP)? Study of how the environment affects the function of plants Requires knowledge of biochemistry, physiology, anatomy and morphology of plants Provides causal, mechanistic explanations for ecological questions such as: - Why does a species live where it does? - How does it survive, and why is that species absent from other environments?

Question: how do plants cope with excess light when it is very cold? e.g. avoid the morning sun

Question: how do plants cope with soils deficient in phosphorus. e. g Question: how do plants cope with soils deficient in phosphorus? e.g. grow cluster roots

Question: how do plants cope with excessive salt? e.g. sequester salt in salt bladders

Question: how do plants manage to grow in deep shade. e. g Question: how do plants manage to grow in deep shade? e.g. use light flecks

Environmental Plant Physiology & Agriculture/Forestry EPP is also closely linked to the study of plant performance in agriculture Agricultural production is limited in many countries by stresses such as drought, nutrient availability, salinity, temperature Need to develop crops that are less sensitive to those stresses, so we can grow them in less favorable environments Understanding required of the physiological mechanisms that enable plants to cope

Question: what mechanisms enable the barley variety on the left cope better with manganese deficiency than the variety on the right?

Environmental Plant Physiology & Global Change Need to predict effect of future changes in global environment on crop productivity, competitive interactions among species etc Also need to know the extent to which plants could reduce future increases in elevated atmospheric CO2

Global atmospheric CO2 concentrations: importance of plants Plant respiration Photo- synthesis

Environmental Plant Physiology & Molecular Biology Mutants/transgenics may allow a rigorous test of hypotheses e.g. transgenic tobacco plants to assess importance of Rubisco (CO2 fixing enzyme in plants) for plant growth

Why so few plant species in one place? Filters Some species do not occur in the UK, because they were never introduced Others arrived, but never made it to maturity Some evolved locally, or were introduced and ‘made it’ Filters are constantly changing/interacting

Response of plants to their environment: time scales Time scale of physiological response is important in determining how a plant copes with changes in the environment e.g. short- and long-term changes in temperature Stress response Acclimation response Adaptation/evolution response Fig. 3. Lambers et al. 1998. Plant Physiological Ecology, Springer. Stress response Occurs over seconds, minutes, hours and days. Will reduce the performance of the plant Acclimation response Morphological and physiological adjustments that occur in individual plants to compensate for the decline in performance. Can result in homeostatic adjustment Adaptation/evolutionary response Results from genetic changes in a population of a plant species, leading to morphological and physiological compensation for the decline in performance caused by stress. Note Not all genetic differences among populations reflect adaptation. Plants may differ genetically because their ancestral species or populations were genetically distinct before they arrived in a particular habitat. Also, not all traits exhibited by a species are necessarily beneficial or that they resulted from natural selection in their environment

Stress and acclimation (of an individual) vs Stress and acclimation (of an individual) vs. adaptation (a long-term genetic response)