It all started to become complicated when the discussion touched on if the important aspect of preserving life is the degree of sentience or life itself. Is life in itself important or is it rather the quality and importance of that life ( defined by its capacity to experience, learn and appreciate ) that makes it important or not. A plant is a living organism and yet ending its life process is not philosophically subject to any moral or ethical standard(s). This type of reasoning obviously does not clearly end the subject because what does one do with a person who is in a coma? Is that life suddenly worthless if we establish it has lost sentience? Again more questions.
It seems easier to start with trying first to agree to a definition of life and then try to see how well that definition fits into our common understanding of 'life' . I say that because some think life is a biological process only, others add consciousness, others consider it an energy and yet again others..... At the basic level when you say to someone Life Loving it seems they feel the meaning and do not ask questions about it. Love being the most wonderful feeling and life the most valuable resource makes us not need to inquire further into details to feel the meaning and to appreciate it.
The backlog to this discussion can be found on the different threads below in English and French and the longest one being the first one ( philosophicalvegan.com ).
http://philosophicalvegan.com/viewtopic.php?f=7&t=3048
https://vegeweb.org/post575129.html#p575129
https://veganforum.org/threads/veganism-life-loving-or-cruelty-free.1426/#post-5698
http://vgnizm.com/veganisme-life-loving-ou-sans-cruaute/
http://vgnizm.com/veganism-life-loving-or-cruelty-free/
So i suggest we start with trying to debate a very common belief such as ' green fingers ' which holds many elements that could at once touch on defining life as well as sentience in that why would plants be receptive to ' natural abilities' if they lack a nervous system? And in that case how do we understand life? Is it the sum of very complex bio-mechanical processes or does it actually extend them? Why is it that it is just as impossible to restore the ' life element ' to an ant as it is to a human being if the organism is much simpler?
So if plants only need certain elements to grow can it be assumed that those elements being applied by a human or a machine would have any differing impact? And if yes then what? and if no then why is there such a common belief? Again there is a saying ' there is no smoke without a fire ' so lets be open minded and curious and inquisitive

From Google:
green fingers
noun
British informal
plural noun: green fingers; plural noun: greenfingers
natural ability in growing plants.
"you really do have green fingers"