2023-09-19-BIOL254-W10-Notes .docx

LECTURE 1: PRINCIPLES OF PLANT PHYSIOLOGY Lecturer: Dr Claudia Meisrimler Introduction To Phytohormones and Signal Transduction In plants, phytohormones and signal transduction are very important in the life cycle of the plants. There are specific phytohormones for each of the stages in the life cyc...

LECTURE 1: PRINCIPLES OF PLANT PHYSIOLOGY Lecturer: Dr Claudia Meisrimler Introduction To Phytohormones and Signal Transduction In plants, phytohormones and signal transduction are very important in the life cycle of the plants. There are specific phytohormones for each of the stages in the life cycle of a plant. From germination to when the plant dies. Phytohormones are also very important for germination. It is also very important for growth as we can see that plants grow in different height, shapes, and sizes. Plants are Sessile Because plants cannot walk around and run from stress, they have complex methods that make them adaptable to stress. They have phytohormones that enable them to respond to their environment through their physiology growth and development. They also use environmental cue to orient in space such as light and gravity. Gravity is important to plants because it helps the roots grow down into the soil or sometimes to branch out. Plants also measure how long the day last (that is daylength) using phytohormones. Plants also regulate temperature, water uptake, opening and closing of the stomata and also measure the time of the way that is winter or summer with the help of phytohormones. Light The important key terms are - Phototropism – growth towards or away from light Photomorphogenesis – development in response to light. This can be seen on germination. Photoperiodism – ability of an organism to detect daylength. Gravity Growth in response to gravity – gravitropism. Temperature Response to extreme changes in temperature such as Response to cold temperature Dormancy – the plant being inactive. Vernalisation – a cold temperature shock for seeds. Eg pine trees seeds. Acclimation to very low temperature Timing of plant responses to the environment is very important. It ranges from very rapid to extremely slow. Adaptation to wind, cold, force can be slow as seen in figure 15.1. Abiotic stresses are those type of stresses that is not caused by an living factor. Internal Co-ordination This is all what happens inside the plant. Orientation of growth (polarity) Co-ordination with the external environment Flowering: - Leaves perceive daylength - Meristems respond by flowering Bud dormancy - Leaves perceive shortening daylength - Buds responds (either opening or staying closed) Tuberization - Wild potato - Leaves perceive the daylength - Underground stolon responds by forming a tuber Note: leaves are essential for sunlight and co-ordination of the external environment not just only for photosynthesis. Tropisms Eg. Gravitropism in roots - Root cap perceives gravity - Cells in elongation zone respond Eg. Phototropism in shoots -Shoot tip perceived light -Cells in elongation zones responds How are these signals perceived? They are perceived on the molecular level. These molecules are called receptors. Response to abiotic stimulus requires a response to a physical stimulus. It requires signal transduction. Signal transduction is a pathway, it is usually one directional pathway. In signal transduction you have, perception/reception of the physical/chemical stimulus. Transduction (from a physical to a chemical stimulus) Transmittance of stimulus , resulting to a biological response ( sometimes can be adaptation)