The finest part of matter is air, of air, soul, of soul, Nous, of Nous, God. CH 6.11
We have known that plants have a respiratory system, that they do breathe, for a long time. In terms of current acceptable scientific understandings, in History of Plant Respiration by Meirion Thomas tells us of Marcello Malpighi (1628 – 1694) who was an Italian Biologist and who’s theories and experiments in London in 1686 formed the basis of much of the nineteenth century work on respiration in plants. Discoveries about the composition of air, and about gaseous exchange between plants and the surrounding atmosphere were made in the late 1700’s. Plants breath.
… therefore nous has taken soul as a cover and the soul, being itself divine, uses breath as fire and the breath governs living things. CH 10.17
…, but all the living (beings) which are endowed with voice have breath and souls, since all that decreases and increases is a living (being). Definitions 4.1
There is a very interesting article National Geographic article, Trees Call for Help—And Now Scientists Can Understand by Gabe Popkin regarding plants making noises other than growing sounds of roots and branches. Plants have both voice and breath.
The Project Augustine theological blog have a great post Plant Theology: Do Plants Have a Soul? (Plant Neurobiology), what I liked about their experiment was the respect shown to the plants, it appeared that there was no negativity directed at the plants during the recording. Plants have the ability to move with intent and sense their environment.
Therefore, the movement of the cosmos and of all living material turns out not to arise from that which comes from outside the cosmos but from what is within, which moves outward: from the soul, from the breath of life or from incorporeal being. CH 2.8
Then there is always this;
Therefore all is immortal: matter, life, spirit, soul and Nous, from which every living creature has been composed. CH12.18