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SELF-SACRIFICE. "In this sense, the senescing leaf continues to function as a source of nutrients to the whole plant, but only at the expense of its own ability to survive." https://lnkd.in/dNWP3KD View in LinkedIn

ABANDONING INDIVIDUAL LIFESTYLES. "In each of these transitions, a group of individuals that could previously replicate independently joins together to form a new, more complex life form that can only replicate as a whole. For example, genes come together to form genomes, cells join together to form multicellular organisms, and multicellular organisms join together to form eusocial societies." http://www.sciencedirect.com/science/article/pii/S0960982213005678 View in LinkedIn

EIGHT MAJOR TRANSITIONS. "The evolution of multicellular organisms represents one of approximately eight major evolutionary transitions that have occurred on earth. The major challenge raised by this transition is to explain why single cells should join together and become mutually dependent, in a way that leads to a more complex multicellular life form that can only replicate as a whole." https://lnkd.in/df8KJQ4 View in LinkedIn

NEW HISTORY. "(i) Cyanobacteria originated before the GOE, (ii) multicellularity coincides with the beginning of the rise of oxygen, and (iii) three clades representing the majority of extant cyanobacteria evolved shortly after the accumulation of atmospheric oxygen." (GOE = Great Oxygenation Event). http://www.pnas.org/content/110/5/1791.full View in LinkedIn

MULTICELLULARITY ROLE. "Our results indicate an origin of cyanobacteria before the rise of atmospheric oxygen. The evolution of multicellular forms coincides with the onset of the GOE and an increase in diversification rates. These results suggest that multicellularity could have played a key role in triggering cyanobacterial evolution around the GOE." (GOE = Great Oxygenation Event). http://www.pnas.org/content/110/5/1791.full View in LinkedIn

SO ENDS a peek into the complexity of the control of leaf fall timing. This is influenced by numerous factors, both internal and external. It remains stunning, to me at least, that despite this complexity, trees march inexorably by species, one by one, exactly in synch, into the autumn leaf coloration and subsequent leaf drop. May your autumns be filled with wonder. View in LinkedIn

ABSCISCIC ACID HORMONE (ABA). "Both the upregulation of genes associated with ABA signaling and a dramatic increase in endogenous ABA levels can be observed in many plants during leaf senescence." https://lnkd.in/dj6JXRP View in LinkedIn

THE ACCELERATOR AND THE BRAKE. "Ethylene is the primary signal that drives the abscission process, whereas auxin reduces the sensitivity of AZ cells to ethylene and thus prevents or delays abscission. Subsequent studies in a variety of species support the idea that applied ethylene can stimulate abscission and that the inhibition of ethylene synthesis or action can delay abscission in many cases." (AZ = abscission zones). https://lnkd.in/dNWP3KD View in LinkedIn

SEVERANCE POINTS. "Abscission of organ systems occurs at anatomically distinct bands of cells referred to as abscission zones (AZs). AZs are often located in stems between the abscising organ and the body of the plant." https://lnkd.in/dNWP3KD View in LinkedIn

DISPOSABLE UNITS. "In some cases, intact, healthy organ systems may be shed as a component of development. The abscission of petals, sepals, and stamen as fruits begin to develop provides an example of this process." https://lnkd.in/dNWP3KD View in LinkedIn