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Ecklonia maxima is a giant brown seaweed growing at the southern tip of Africa at the astonishing speed of up to 3 cm per day. One unique feature of Ecklonia maxima is its unusually high content of auxin in combination with a much lower cytokinin value leading to probably the highest auxin to cytokinin ratio known in plants. Auxin and cytokinin are two of the 5 major classes of plant hormones. In general, plant hormones control every aspect of plant growth and development. Plant hormones are produced in very small concentrations, but even a minute amount can have a profound effect. Reactions to plant hormones always depend on their relative concentrations compared to other hormones present. It is the hormonal balance that controls the growth and development of each plant. Auxin was the first plant hormone detected. The most prominent auxin is IAA (Indol-3-acetic acid). IAA is synthesised from tryptophan or indole primarily in leaf primordia, young leaves and in developing seeds. Auxin is the key plant hormone as it not only initiates different effects but also controls the action of all other plant hormones like cytokinin and gibberellin. Key effects are: Cell enlargement and stem growth Root initiation Tropistic responses (gravity and light) Apical dominance Delay of leaf senescence Delay (and promotion) of leaf and fruit abscission in some plants Fruit setting and growth Promotion of flowering Growth of flower parts Cytokinin is adenine derivates with the ability to induce cell division in tissues in the presence of auxin. Cytokinin is synthesized in root tips and developing seeds. Key effects are: Cell division – in tissues after exogenous application in the presence of auxin, endogenous in gall tumours on plants. Present in actively dividing cells Growth of lateral buds Leaf extension by cell enlargement – adjustment of total leaf area to growth of root system Delay of leaf senescence Enhancement of stomata opening (in some species). The other key plant hormones are gibberellins, ethylene, and abscisic acid. Gibberellins are synthesised in young tissues of the shoot and developing seeds and initiate stem growth, fruit setting and growth (with exogenous application) and induce germination (instead of cold or light). Ethylene is synthesized in many tissues in response to stress, and is the fruit ripening hormone. In particular, it is synthesized in tissues undergoing senescence or ripening. Abscisic acid is synthesised in roots and mature leaves, particularly in response to water stress with the key effects of stomata closure, inhibition of shoot growth and induction of storage protein synthesis in seeds. Additionally, many more plant hormones have been detected. Amongst others are polyamines, brassinosteroids, jasmonates, peptides, salicylic acid which all mainly play a role in plant defence mechanisms. Balance of auxin and cytokinin: In the 1950’s a series of experiments showed how the ratio between auxin and cytokinin works. If auxin is added to a plant then the cells grow very large but they don’t divide. If cytokinin is added - and auxin is present - then the plant cells divide. Therefore, the ratio of auxin to cytokinin determines how the cells will differentiate. In young plants, a surplus of auxin will initiate root growth. A higher concentration of cytokinin will support the development of shoots and shoot buds. If the concentrations of both are equal then the plant cells will grow but will remain undifferentiated. The exogenous application of auxin will promote root growth and initiate the synthesis of cytokinin in the root meristem. These freshly produced cytokinin will signal the plant to grow more shoots, leading to a naturally balanced bigger and stronger plant.