Plant Development_ Spr24 BIOL 010B #35557 THE DIVERSITY OF LIFE ON EARTH-Hybrid.pdf

Plant Development For this page, I have pulled specific text from the paper: Depuydt, S., & Hardtke, C. S. (2011). Hormone signalling crosstalk in plant growth regulation (https://canvas.pasadena.edu/courses/1140356/files/78495981?wrap=1). Current Biology, 21(9), R365- R373. You can also read about...

Plant Development For this page, I have pulled specific text from the paper: Depuydt, S., & Hardtke, C. S. (2011). Hormone signalling crosstalk in plant growth regulation (https://canvas.pasadena.edu/courses/1140356/files/78495981?wrap=1). Current Biology, 21(9), R365- R373. You can also read about the role of plant regulators (i.e. plant hormones) in Campbell Chapter 39 or OpenStax Chapter 30 (https://openstax.org/books/biology-2e/pages/30-introduction) A central feature of plant development is the largely post-embryonic formation of the plant body. While in animals practically all organs are formed during embryogenesis and elaborated during the juvenile stage, plant embryogenesis results in the formation of a miniature plant. This socalled seedling possesses discrete stem cell pools in the shoot and root meristems, which form the vast majority of plant organs post-embryonically in a modular, reiterative fashion that also integrates environmental inputs. The shoot apical meristem and the lateral meristems derived from it give rise to the above-ground organs such as stems, leaves and flowers, while the root apical meristem forms the root system with its branches. The advantage of this modular, post-embryonic mode of development is that it provides an appropriate response to environmental stimuli, which are of pivotal importance in plant development given that plants are sessile and thus have no choice but to adapt to their immediate environment. Such adaptation does not involve only physiological processes, for example to cope with given levels of soil salinity, but also significant morphological changes, for example the so-called shade avoidance response that favours exaggerated elongation growth. Plant growth and development are controlled by both external cues and intrinsic growth regulators, such as hormones. Mounting evidence suggests that environmental cues target the biosynthesis or perception of hormones, which therefore not only orchestrate intrinsic developmental programs, but also convey environmental inputs. Eight principal classes of plant hormones have been characterized: abscisic acid, auxin, brassinosteroids, cytokinins, ethylene, gibberellins, jasmonates and strigolactones. All of them have been linked to growth regulation in one way or another, sometimes in a context-specific manner.  Gibberellins Gibberellins have a major influence on germination, plant growth in general (mainly via cell expansion), floral development and flowering time. Auxin Auxin signalling is essential for embryogenesis and defines the later growth axes of the plant. In the root meristem, auxin action is shaped through polar auxin transport and determines root system growth and its branching pattern. In the shoot apex, auxin accumulation at the sites of primordia is essential for lateral organ formation. Auxin activity is also observed in floral organ primordia, ovule primordia and zygotes. Brassinosteroids Brassinosteroids have been reported in almost all plant tissues, with highest levels found in seeds, pollen and young growing tissues. Brassinosteroids act largely postembryonically with pronounced effects on general plant growth via cell elongation, vascular differentiation, and reproductive development. Ethylene Abscisic Acid Promotes ripening of many types of fruit, leaf Inhibits growth, promotes stomatal closure abscission, and the triple response in seedlings, during drought stress, promotes seed dormancy enhances the rater of senescence, promotes and inhibits early germination, promotes leaf root and root hair formation, promotes flowering senescence, promotes desiccation tolerance in the pineapple family Cytokinins Jasmonates Regulate cell division in shoots and roots, modify Regulate fruit ripening, floral development, apical dominance and promote lateral bud pollen production, tendril coiling, root growth, growth, promote movement of nutrients into sink seed germination, and nectar secretion, tissues, stimulate seed germination, delay leaf produced in response to herbivory and pathogen senescence invasion Strigolactones Promote seed germination, control apical dominance, and the attraction of mycorrhizal fungi to the root