12942 - Molecular Physiology of Plants

Learning outcomes

At the end of the course, the student assimilates with critical insight and in depth analysis, the main themes of plant physiology and their molecular basis (transport, photosynthesis, metabolism, mineral nutrition, hormonal regulation and photomorphogenesis).

Course contents

Module 1  
Introduction: Arabidopsis thaliana as a model species in molecular plant physiology.

Plant-water relationships. Chemico-physical characteristics of water. The movement of water: diffusion, mass flow and osmosis. Electrochemical potential and water potential. Water and plant cells. The water balance of the plant. Root absorption. Xylem transport. Transpiration. Earth's water availability. Water use efficiency and plant productivity.
Membrane transport. Proton pumps and other pumps of plant cells. The proton-ATPase of the plasma membrane: structure, mechanism of action, regulation. Membrane potential and electrochemical potential. Role of ion transport in stomata movements.

Mineral nutrition and assimilation. Essential nutrients. Mineral nutrition in agriculture. Mycorrhizae. Strategies of iron absorption in grasses versus dicots and non-grasses monocots. Nitrogen: deficiency and excess. Absorption and reduction of nitrate to ammonium. Assimilation of ammonium (GS-GOGAT). Aromatic amino acid biosynthesis: glyphosate and transgenic plants.

Photosynthesis (light phase). Light, solar emission and atmospheric absorption, PAR light, light energy. Anatomy of chloroplasts. Photosynthetic pigments. Excitation energy dissipation. Concept of photosystem. Structure of photosystem II reaction center, internal antenna, external antenna, a oxygen evolving complex, supramolecular organization. Relationship between redox potential and energy of light. Z-scheme. Structure of photosystems. Photolysis of water. Cytochrome b6f. Bioenergetics of photophosphorylation. Photosynthetic electron transport: non-cyclic (linear), cyclic and pseudo-cyclic. Distribution of photosystems in thylakoids. State I-state II transition. Quantum yield of cyclic and linear electron transport.

Module 2

Photosynthesis (metabolism). Carbon metabolism. Calvin cycle and its light/dark regulation. Relationship between Rubisco oxygenase and carboxylase activities. Photorespiration. Gross and net photosynthesis. Compensation point for CO2 and internal concentration of CO2. Mechanisms of concentration of CO2: C4  and CAM plants. Metabolic relationships between starch and sucrose. Sink/source relationships. Degradation of primary starch in the dark. Phloem: anatomy and cytology. Composition of the phloem sap. Phloem transport. Water relations between phloem and xylem.
Respiration. Functions of respiration in plants. Conversion of sucrose into hexoses. Plastid and cytosolic glycolysis. Bypasses of cytosolic glycolysis. Pentose phosphate pathway and differences in regulation between cytosolic and chloroplastic pathway. Krebs cycle. Respiratory chain: external and internal NAD(P)H dehydrogenases, alternative oxidase, uncoupling protein. Stoichiometry ATP / H + of the mitochondrial ATP synthase.

Photomorphogenesis. Scoto- and photo-morphogenesis. Classes of plant photoreceptors. Phytochrome: molecular structure, photoconversion, absorption spectrum, photostationary state, action spectrum. Nuclear translocation of Pfr and modification of gene expression. Family of PHY genes and multiplicity of responses. Cryptochromes: structure and function. Role of cryptochromes in de-etiolation and hypocotyl elongation. Fototropine. Biological clock.    

Hormones. General concepts. Auxins: polar auxin transport and transport in the phloem. Role of IAA role in cell expansion. IAA and phototropism. IAA and positive gravitropism of the root. Gibberellins, effects on germination and plants height. Regulation of gene expression mediated by GA. GA signaling pathway. Cytokinins: perception and signal transduction. Cell cycle control. Abscissic acid: perception and signal transduction, regulation of stomata closure. Ethylene: perception and signal transduction, fruit ripening.

Readings/Bibliography

Rascio N, Carfagna S, Esposito S, La Rocca N, Lo Gullo MA, Trost P, Vona V (2012) Elementi di Fisiologia vegetale. EdiSES

Teaching methods

The course will consist of lectures accompanied by the projection of pictures and diagrams (power point). Questions and requests of further explanation from the students are always welcome, both during and after the lesson.

Assessment methods

Verification will be performed by oral examination, but the student will be asked to show on paper the structure of biochemical formulas, metabolic pathways, reactions, etc..

Teaching tools

The course will take place in classrooms with PC projection. All lectures will be given with power point presentations. The files of power point presentations will be made ​​available to students at the end of the course (downloadable files from AMSCAMPUS).

Office hours

See the website of Francesca Sparla