|32: ...focuses... ... is not encouraged...|
37-38: It also includes diffusion among mesophyll cells in the liquid phase, and diffusion through the mesophyll in the vapor phase. Vapor-phase transport affects water potentials of all tissues downstream from the leaf xylem, so it must be considered part of "water transport" even though we may prefer to think of "water transport" as ending at the sites of evaporation. Water transport in plants may also include liquid-phase bulk flow through the apoplastic spaces in the mesophyll, and either diffusion or effusion through plasmodesmata, although the importance of those latter two pathways is largely speculative.
39: please define the symbols in the text here, or better, make a table listing all symbols, units, etc., and then refer to the table at line 39.
39: at the end of this sentence, it may help to explain for readers why you're saying this about the ions: namely, that osmotic potential does not contribute to the driving forces for long-distance transport in the xylem, because (1) the reflection coefficient in the xylem is zero, and (2) the distances involved are too long for diffusion and thus chemical potential to be an important contributor.
41: The symbol "psi_m" for osmotic potential is likely to generate confusion. I suggest you use "psi_s" or reverse the sign convention and use greek "pi" for osmotic pressure. psi_m looks like matric potential or mesophyll water potential to me.
line 43: There is actually a general name for Px + rho*gh, which is the "head" (or hydraulic head).
48-49: This example illustrates *how* delta psi might not equal delta P, but it doesn't explain *why* delta P is the correct driving force in this context instead of delta psi. That explanation is the one I gave in my first review, about the relevance of different modes of transport (bulk flow vs diffusion) at different spatial scales. Since the purpose of this ms is to clarify these issues and prevent confusion and error, I really think it's necessary to explain this point explicitly.
56: The criteria for the delta values to be equal are a bit more strict than this – it also assumes the osmotic potential in the xylem is zero. It's typically pretty small, as you noted earlier, but not zero. And there are circumstances where it's not negligible.
61: I used the word "sophistic" in my review in a different context; I wouldn't say the use of leaf water potential is a "sophistic mistake". You could say a "mistake of interpretation" or just mistake.
Also, on 61, the first sentence needs to be linked to the second to make sense. Perhaps "A commonly seen mistake is the use of leaf water potential to describe measurements from the pressure chamber method (Scholander...), which gives a decent estimate of the xylem water potential. People often refer to this measurement as leaf water potential because..."
63: should add to this list: (c) provided the leaf has been allowed to equilibrate internally prior to the pressure chamber measurement, the water potential in the xylem should equal that in the mesophyll.
65: "For example, when the whole plant is under equilibrium, leaf water potential should be equal everywhere, but the measured leaf xylem pressure would differ for leaves at different height." The first part of this sentence is incorrect (if you interpret water potential as a measurable) or inadvertently misleading (if you interpret it to include the un-measurable "gravitational component"). *Measured* leaf water potential (e.g. by psychrometry or the Shardakov method) would not be equal everywhere; assuming no solutes in the xylem, leaf water potential would necessarily equal xylem water potential everywhere, which in turn would equal xylem pressure (if no solutes). Now, that's not true if you include the 'gravitational component', but including that term is always confusing because *it cannot be measured* – any method of measuring WP involves chemically equilibrating the leaf's water with some other pool of water whose potential is either known (as in Shardakov) or can be measured (as in the vapor in the psychrometer chamber), and that act of chemical equilibration requires the two pools of water to be close enough that the gravitational component can't differ measurably. Something that cannot be measured in practice and only exists in a theoretical definition is only going to generate confusion... unless you tackle the confusion head-on. I realize this issue is confusing for readers, but again, if this ms is to serve its intended purpose, it should tackle these difficult issues openly!
73: I think the proper term here is "extensive" properties, not bulk properties. They are extensive because their numerical values depend on the extent (size) of the system. e.g., flow rate will be greater for 10 xylem conduits taken together than for just one conduit, whereas flux (flow per cross sectional area) would be the same in both cases, and would be an "intensive" quantity.
74: It's true that xylem structure is often highly non-uniform, but you could say the same thing about electrical properties of most realistic things in nature. The electrical vs hydraulic distinction doesn't really clarify here. What matters is that "conductivity" is meant to describe an intensive property.
76: Using "E" for flow rate here could confuse readers, because it so often means "transpiration rate", which in turn is conventionally expressed on a leaf area basis – so k would then look like a conductivity because E would look like a flux.
77: I'm not sure what you mean by "and area not accounted for by k".