12942 - Molecular Physiology of Plants

Learning outcomes

At the end of the lectures, the student acquires current and detailed knowledge on the basic molecular mechanisms allowing the functioning of plants (photosynthesis, metabolism, mineral nutrition, photomorphogenesis and hormonal regulation).

Course contents

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

Plant-water relationships. Water and plant cells. The water balance of the plant. Root absorption. Xylem transport. Transpiration. The proton-ATPase of the plasma membrane. Role of ion transport in stomata movements. Water use efficiency and plant productivity. 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.

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.

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. EdiS

Teaching methods

The course will consist of lectures accompanied by the projection of pictures and diagrams. 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

Teaching tools

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

Office hours

See the website of Francesca Sparla