70
WALLACE H. FULLER
stage of their growth cycle and many kinds of plants are excluded from
desert environments because of this.
3. Specific Effects of Salt
The distribution and concentration of native desert vegetation is markedly influenced by the kind and nature of the salts in soils. Chlorides in
soils may be sufficiently high to accumulate in leaves and cause yellowing,
tip and marginal burn, and finally leaf shedding. Certain plants will accumulate sodium in their leaves, whereas others will not. Sodium also may
disperse the soil sufficiently to lower oxygen tension and reduce water uptake, particularly if the soils are fine textured (McGeorge and Breazeale,
1938; Hayward and Wadleigh, 1949; Richards, 1950). Salt and sodium
in French Somaliland soils adversely affect vegetable crop production
(Tkatchenko, 1951). The principal reasons are attributed to (1) deficient
organic matter, (2) nonavailability of nutrients, (3) poor physical condition of the soil, (3) inadequate quantity of irrigation water, and (4) high
osmotic pressure in the soil solution. In the Negev in Israel four kinds of
native plants are classified according to their salt tolerance: (1) chlorideabsorbing xerohalophytes having high osmotic potentials, (2) chlorideabsorbing hydrohalophytes also having high osmotic potentials, (3)
xerohalophytes absorbing salts other than chlorides having medium osmotic potentials, and (4) nonhalophytic xerophytes having low osmotic
potentials (Tadmor et al., 1962). The chloride and sulfate content of
native plants has been shown to be correlated with the chloride and sulfate
content of the soil on which they grow (Akzhigitova, 1959). Excess lime in
soils has been found to induce iron deficiency called, "iron-induced" chlorosis (McGeorge, 1949; Thorne, 1951; Thorne and Peterson, 1950) in
soils of Western United States. The bicarbonate ion also produces a symptom in plants similar to "lime-induced" chlorosis (Wadleigh and Brown,
1952).
4. Salt-Injury Symptoms
In a review of vegetation of desert regions in the sierozem zone of Central Asia, Rozanov (1951) discusses the close relationships he observed
between specific plant species and their presence on specific desert soil
types. The occurrence of a specific plant species or dominance of certain
colonies of species on a given desert soil type is related primarily to the
moisture relationships in the root zone and the quantity and quality of
soluble salts. The cation elements, usually in excess in desert soils are
sodium, potassium, magnesium, and calcium, and the anions, Cl", S0 4
2
~
and HCO-f. Borates, nitrates, lithium, and selenium excesses have been reported also but are not as common. Bernstein (1964b) suggests that salt
WALLACE H. FULLER
stage of their growth cycle and many kinds of plants are excluded from
desert environments because of this.
3. Specific Effects of Salt
The distribution and concentration of native desert vegetation is markedly influenced by the kind and nature of the salts in soils. Chlorides in
soils may be sufficiently high to accumulate in leaves and cause yellowing,
tip and marginal burn, and finally leaf shedding. Certain plants will accumulate sodium in their leaves, whereas others will not. Sodium also may
disperse the soil sufficiently to lower oxygen tension and reduce water uptake, particularly if the soils are fine textured (McGeorge and Breazeale,
1938; Hayward and Wadleigh, 1949; Richards, 1950). Salt and sodium
in French Somaliland soils adversely affect vegetable crop production
(Tkatchenko, 1951). The principal reasons are attributed to (1) deficient
organic matter, (2) nonavailability of nutrients, (3) poor physical condition of the soil, (3) inadequate quantity of irrigation water, and (4) high
osmotic pressure in the soil solution. In the Negev in Israel four kinds of
native plants are classified according to their salt tolerance: (1) chlorideabsorbing xerohalophytes having high osmotic potentials, (2) chlorideabsorbing hydrohalophytes also having high osmotic potentials, (3)
xerohalophytes absorbing salts other than chlorides having medium osmotic potentials, and (4) nonhalophytic xerophytes having low osmotic
potentials (Tadmor et al., 1962). The chloride and sulfate content of
native plants has been shown to be correlated with the chloride and sulfate
content of the soil on which they grow (Akzhigitova, 1959). Excess lime in
soils has been found to induce iron deficiency called, "iron-induced" chlorosis (McGeorge, 1949; Thorne, 1951; Thorne and Peterson, 1950) in
soils of Western United States. The bicarbonate ion also produces a symptom in plants similar to "lime-induced" chlorosis (Wadleigh and Brown,
1952).
4. Salt-Injury Symptoms
In a review of vegetation of desert regions in the sierozem zone of Central Asia, Rozanov (1951) discusses the close relationships he observed
between specific plant species and their presence on specific desert soil
types. The occurrence of a specific plant species or dominance of certain
colonies of species on a given desert soil type is related primarily to the
moisture relationships in the root zone and the quantity and quality of
soluble salts. The cation elements, usually in excess in desert soils are
sodium, potassium, magnesium, and calcium, and the anions, Cl", S0 4
2
~
and HCO-f. Borates, nitrates, lithium, and selenium excesses have been reported also but are not as common. Bernstein (1964b) suggests that salt