Sweet taste soft pleasant smell and color changes these are brought about by

Sweet taste soft pleasant smell and color changes

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Sweet taste, soft, pleasant smell, and color changes-- these are brought about by the hormone ethylene Commercial fruit growers can harvest and ship unripe fruits and speed up the ripening with ethylene application Conversely, CO2 slows down the ripening, therefore fruit can be shipped and stored in an atmosphere of CO2 to delay ripening until the fruits reach the market
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(Lec 1: Les 5) 5 Transgenetic tomatoes with an altered ethylene synthesis gene like in the figure are one of the first genetically modified crops available for human consumption Ethylenes also has other roles in promoting abscission and in defense Abscisic Acid- growth suppressant and dormancy ABA does not play a role in abscission but is important in maintaining dormancy in winter buds and seeds In these roles, ABA seems to counteract the effects of other hormones that promote growth and germination such as auxin and gibberellins To break dormancy, the levels of ABA must decrease in the buds and seeds ABA also influences the closing of stomata by triggering the movement of potassium ions out of the guard cells Reproductive Development In our lesson of plant diversity, we learned about the reproductive innovations of flowers and fruits that allowed angiosperms to be the most successful land plant The life cycle of a flowering plant as in the top right figure shows that flower production is just one phase of development and in this regard, plants are similar to animals Once plants reach reproductive maturity, they must gain competence to respond to internal signals and to environmental queues that regulate flowering as shown in the bottom model The signals turn on genes as they specify the formation of the flower structures: sepals, petals, stamens, and carpels Transition To Flowering The process of becoming competent is called Phase Change Sometimes phase change is obvious as shown in the photographs in the top figure The oak tree on the left has lower juvenile branches and the leaves are not capable of producing an abscission layer necessary for shedding the leaves The upper branches are in the adult phase The Ivy plants on the right picture show a mature plant producing flowers in a juvenile plant. Note the difference in leaf pattern The juvenile plant will also be able to cling to structures with advantageous roots while the adult plant does not produce these roots Once phase change occurs, other factors may be necessary to occur to trigger flowering Flower Production There are four genetically regulated pathways for flowering The light-dependent and temperature-dependent pathway depend on external queues Gibberellin dependent pathway requires an increase in the hormone levels the autonomous pathways doe snot depend on external queues except for nutrition The figure shows a model for flowering Before flowering pathways lead to an adult meristem becoming a floral meristem by either activating flower promoting genes or inhibiting flower repressor genes Two of the key floral meristem identity genes LFY and AP1 These genes turn on floral organ identity genes that define the 4 floral parts Light Dependent Pathway
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(Lec 1: Les 5) 6 Light Dependent Pathway is a photoperiodic response Photoperiod
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