What do we know about plant senescence?

I watched this video by a home gardener on squash vine borer & zucchini.


What really grabbed my attention was that one of his four zucchini plants was not senescing whereas the other three were (and one of those was rapidly succumbing to SVB).

Presumably leaf Brix declines with plant senescence (does it?) & delaying senescence would increase yield & pest resistance.

Why was senescence delayed in that one zucchini plant?

Another video, this time from James Prigioni on increasing cucumber yields:
https://youtu.be/Q7Pg5MYJZKM

He points out a few things of interest relating to senescence in cucurbits. One is well-known - if you want to prolong production you need to harvest fruits while they are immature. There must be a signal from the mature fruit to the main plant that triggers senescence. He says cucurbitacin is a bitter compound that attracts cucumber beetles & big, overly mature cucumbers are bitter - so perhaps cucurbitacin is the signal. Interesting the bugs like the bitter compound; often the bitter compounds are phytoalexins. Perhaps the cucurbitacin  is the beetle's cue that plant is senescing & therefore has lower leaf Brix? (but I have still have not confirmed whether my assumption  about leaf Brix & senescence is correct)

Did a search & found out that cucurbitacin triggers senescence in colon cancer cells - how's that for cross-kingdom signalling!
https://pubs.acs.org/doi/abs/10.1021/acs.jafc.1c07952

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sort of unrelated - Prigioni also says it's the cucurbitacin that causes some people to burp when they eat cucumber so I'm wondering if it also somehow affects carbonic anhydrase (enzyme for CO2/bicarbonate interconversion) activity.

yet another video, this time from Advancing Eco Agriculture, 'Why Plant Disease Increases Before Harvest'
https://youtu.be/dAPhmxCOqqQ

mainly on auxin / cytokinin balance, but touches on senescence briefly. Ethylene is the senescence hormone produced in fruit.

my comments: do you really want to decrease auxin / cytokinin ratio in fruiting plants since auxin (according to video) moves sugars into fruit? Would you be trading pest resistance for taste/fruit quality?
Overall I find AEA video series interesting, but would prefer more review of scientific evidence; anecdotes (like the example of mites in corn) are interesting but scientific studies are needed.

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Papers I've skimmed say that cucurbitacin is anti-insect, but that some pests have evolved resistance & even use it to deter their own would-be predators. That dang evolution thing again.
Hydrogen sulfide is an anti-senescence signalling molecule in plants & is associated with cucurbitacin production, so there goes all my idea on cucurbitacin as being somehow related to senescence in plants (but it is in cancer cells, go figure).
https://pubmed.ncbi.nlm.nih.gov/30707394/

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Article on using Chlorella supernatant (the leftover culture medium from growing Chlorella) to delay senescence:
https://www.tandfonline.com/doi/pdf/10.1080/15592324.2020.1763005?needAccess=true
my comments: main constituent is lactic acid, could be obtained from other sources. LA is a reducing agent and it is possible other reducing agents would also work.

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So there is a literature base on plant senescence in relation to crop yields, but many use term 'leaf senescence'. So leaves will senescence in annuals as they do seasonally in perennials, but in annuals I expect there is also root senescence. Perhaps root senescence is main driver in annuals & that's why auxin / cytokinin balance is so important?

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Anyway, I continue to read up on the topic as time allows. If anyone has any links to good podcasts/videos please post as I am able to listen/watch as I do chores - my time for reading literature is limited, unfortunately.

Just a link if interested although the articles are behind a paywall.  The article noted below is a more recent offering of articles on senescence that date back several decades in this review series.  Just in case it helps in some way....