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(Upload on February 5 2017) [ 日本語 | English ]

Water ()






Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

[ water potential | pH ]

Water for life (生命にとっての水)
Plants live with water because of photosynthesis (光合成)

Plants [ algae | moss | fern | seed plant ]
Physiology [ water culture , water stress ]
Ecology [ hydrosphere | wetland ]

索引

Water transportation (水移動)



(Slatyer & Taylor 1960)

Water potential (水ポテンシャル)

Quantifier: ψ, or ψw
Dimension: L-1MT-2
Unit: Pa

Water transport: from high to low water potential →
The following equation is ture whenever water transportation occurs from soil to air through plant

ψl < ψx < ψr < ψs
← ← ← ← ← ←
l: leaf, x: xylem, r: root, s: soil

Law. Darcy's law (ダルシーの法則, Darcy 1856)
ψh = ψm + ψg (Pa or cm)

ψh: hydraulic potential (water potential)
ψm: tention (張力)
ψg: relative height of the quantity of water in the gravitational field

Darcy J = -K·(dh/ds) (m3/m2s = m/s)

J: flux rate
K: hydraulic conductivity (透水係数)

K = K(φm(Θ))

Θ: volume fractiion of the bulk soil containing water
Q = KAt·h/l = K·D

t: unit time

Permeability (浸透性)
Terms: permeable, adj 浸透(透過)される, permeate, vt -に浸透する

Deficiency and evapotranspiration (etp)

Ideal

water potential water potential

Actual

water potential water potential
-ψπ: osmosis potential, -ψp: water potential, -ψ: equivalent state

Active transport (水能動輸送)

Materials: Barley roots
active transport
active transport

[ stable isotope ( 安定同位体 )]

Water for plant (植物における水)


Def. transpiration (蒸散), Tp: the evaporation of water from plants

stomatal transpiration
cuticular transpiration
lenticular transpiration

Vapor water deficit (VPD, 飽差)

Water-use efficiency, WUE (水利用効率)

Def. WUE: the ratio of water used in plant metabolism to water lost by the plant through transpiration (at a unit time)
a) instantaneous water-use efficiency (photosynthetic WUE)

ratio of the rate of carbon assimilation (photosynthesis, Ps) to the rate of transpiration
= Ps/Tp

b) integrated water-use efficiency (water-use efficiency of productivity)

the ratio of biomass (dry weight, Dw) produced to the rate of transpiration
= Dw/Tp

Transpiration ratio (蒸散係数) = water requirement (要水量)

the amount of water required to produce a unit of plant biomass
= 1/WUE

crop ≈ 200-1000: 200-1000 kg of water is requred to prodcue 1 kg of biomass

pH (potential of hydrogen, ピーエッチ)


A measure of the acidity or basicity of an aqueous solution, expressed by the concentration of hydrogen ion
Def. ionic product of water (水のイオン積), Kw ≡ [H+]·[OH-]

→ depending only on temperature (T)
Ex. room temperature → Kw ≈ 1.0 × 10-14

T (°C) → Kw
0 → 0.113 × 10-14
10 → 0.292 × 10-14
20 → 0.681 × 10-14
25 → 1.008 × 10-14

Def. Hydrogen-ion exponent (水素イオン指数), pH = -log[H+]
= Potential hydrogen, or power of hydrogen
pH is defined as minus the decimal logarithm of the hydrogen ion activity in a solution. So, pH is a dimensionless quantity.

pH = -log10(H+) = log10(1/H+),

where H+ is the activity of hydrogen ions.
As wall as pH, we can define pOH = -log[OH-], and pKw = -logKw
→ pKw = pH + pOH = 14
Ex. Pure water: H2O ⇔ H+ + OH- → [H+] = [OH-] = 10-7

K = [H+][OH-]/[H2O] = 1.8 × 10-16 (mol) = 55.5 (mol)

[H+][OH-] = 1.8 × 10-16 × 55.5 = 1.0 × 10-14, [H+] = [OH-] = 1 × 10-7 ∴ pH = log[H+] = 7

pH_____0____1____2_____3____4____5_____6____7
[H+]___100__10-1__10-2__10-3__10-4__10-5__10-6__10-7
[OH-]__10-14_10-13_10-11_10-12_10-10_ 10-9__10-8__10-7
______acidic ←←←←←←←←←←←←←←←← neutral
____________→→→→→→→→→→→→→→→→ alkali
pH__________8____9____10___11___ 12___ 13___ 14
[H+]________10-8_ 10-9__10-10_ 10-11_10-12_ 10-13_10-14
[OH-]_______10-6_ 10-5__10-4__10-3__10-2__10-1__100

Def. H+ activity (プロトン活量)

CH+ = r[H+]

r: activity coefficient (活量係数)
fA: [H+]↑ → r = 1, [H+]↓ → r > 1

Ex. 0.1 M HCl: -log[H+] = 1.09 = log-1(2.91) = 8.1 × 10-2, r = 0.81

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