Growth, Nutrition, and Water Uptake of Tomato Plants with Divided Roots Growing in Differentially Salinized Soil1
- I. Papadopoulos,
- V. V. Rendig and
- F. E Broadbent2
Tomato (Lycopersicon esculentum Mill. var. VF 145) plants were grown in the greenhouse to determine effects of uniform and nonuniform salinity distribution on root growth and on water and N uptake. The plants were grown in Reiff sandy loam (Coarse-loamy, mixed, nonacid, thermic Mollic Xerofluvents) using a technique by which the root system was divided and each of four quadrants allowed to grow in separate compartments. Nutrient solutions differing in salinity levels (1, 4, 7, and 10 dS/m; nonuniform treatment) were applied to the four compartments, or all four received a nutrient solution otherwise similar but with a salinity of 5.5 dS/m (uniform treatment). The salinization was brought about by a mixture of NaCl and CaCI2 in a ratio of 1:l by weight. To determine sources of N taken up, sufficient K15NO3 was added to provide 2% l5N in the solution. Yields of shoots and roots were lower for the plants grown with the uniform than the nonuniform salinization treatment. With nonuniform salt distribution, about 62 and 8% by weight of the total root system were found in the compartments irrigated with nutrient solutions having initial salinities of 1 and 10 dS/m, respectively. About 63% of the total water taken up per plant was drawn from the compartment with the lowest salinity. With the uniform salt distribution treatment, N uptake into the shoots was more severely affected than growth. With treatments in which salinity was nonuniformly distributed, the main source of N was the compartment with the lowest salinity. The contribution of this compartment, however, decreased during the growing period as its relatively greater salinity buildup favored uptake of N by roots in the other compartments, initially irrigated with the more saline solutions. Plants growing in the units with the nonuniform salinity treatment generally showed lower leaf concentrations of Ca, Na, K, and Cl, but higher leaf concentrations of Mg and P than the plants growing in the uniformly salinized units. Unlike the other elements, K and P concentrations decreased with time. Differences in S concentrations as related to salinization treatments were variable during the growth period. Higher concentrations of the “bound” organic anion fraction, but lower concentrations of the “diffusible” fraction, as determined from differences in amounts of inorganic cations and anion present, were found in leaves of plants grown with the higher salinity levels. In general, for nutrition of tomato plants grown under conditions in which different regions of the root system are exposed to differences in salinity, the least saline environment is dominant, but over time root activity shows some accommodation to the presence of salt.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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