Plant Growth and Development Photosynthesis Transpiration Respiration Photosynthesis

Plant Growth and Development 清華大學生命科學系 林彩雲

Photosynthesis Transpiration Respiration

Photosynthesis Carbon dioxide + Water + Sunlight = Sugar + Oxygen Or 6 CO 2 + 6 H 20 + Energy => C 6 H 1206 + 6 02

Photosynthetic organisms leaves from higher plants flanked by colonies of photosynthetic purple bacteria (left) and cyanobacteria (right)

Increasing CO 2 levels The light reactions of photosynthesis stop when the sun goes down However, CO 2 fixation can continue as long as ATP and NADPH is available In cacti and other succulents CO 2 uptake by the plant occurs primarily at night

Respiration C 6 H 12 O 6 + 6 O 2 => 6 CO 2 + 6 H 2 O + Energy Photosynthesis Respiration • produces food • stores energy • uses water • uses carbon dioxide • releases oxygen • occurs in sunlight • uses food • releases energy • produces water • produces carbon dioxide • uses oxygen • occurs in the dark as well as light

Glycolysis, breakdown glucose to pyruvic acid in cytosol Complete oxidation of pyruvic acid to carbon dioxide and water NADH dehydrogenase succinate dehydrogenase cytochrome c reductase (cytochrome b-c 1 complex) cytochrome c oxidase ATP synthase

WHY DO LEAVES CHANGE COLOR IN THE FALL?

Transpiration Transporting minerals from the soil throughout the plant Cooling the plant through evaporation Moving sugars and plant chemicals Maintaining turgor pressure

Evaporation

Condensation

Precipitation

A balancing act

Environmental Factors Affecting Growth Light Temperature Water Humidity Nutrition

Plants in communities Plant or landscape ecology Succession Available light and moisture Competitive weeds thrive Allelopathy Relationships between plants and pollinators, animals, birds, pests, predators

Plant hormones and growth regulators Auxin Gibberellin (GA) Cytokinin Ethylene Abscisic acid (ABA)

Auxin caused responses Bending toward a light source (phototropism) Downward root growth in response to gravity (geotropism) Promotion of apical dominance Flower formation Fruit set and growth Formation of adventitious roots

Gibberellins Stimulate cell division and elongation Break seed dormancy Speed germination

Cytokinins Stimulate cell division A medium's mix of growth-regulating compounds is high in cytokinins and low in auxin, the tissue culture explant (small plant part) will produce numerous shoots Cytokinins also are used to delay aging and death (senescence)

Ethylene Induces ripening Causes leaves to droop (epinasty) and drop (abscission) Promotes senescence

Abscisic acid (ABA) A general plant-growth inhibitor Induces dormancy and prevents seeds from germinating Causes abscission of leaves, fruits, and flowers Causes stomata to close