Zonal Salinization of the Root System in Relation to Plant Growth

Abstract

Corn and tomatoes were grown in the greenhouses in boxes containing three horizontal soil zones with a layer of coarse quartz sand to separate the zones. Either fresh or saline waters were supplied to each soil zone through porous ceramic tubes to maintain a fairly uniform water suction in each zone. Intro duction of saline water into a given zone caused the uptake of water by the plant from that zone to decrease as soil salinity increased to a critical value, at which point water uptake ceased. The amount of water taken up by the plant from the nonsaline zones increased so that the total amount of water taken up by the plants was slightly less where onethird of the soil was salinized as compared with the nonsalinized treatment. Water uptake further decreased where twothirds of the root system was salinized. Plant growth was unaffected when one third of the root system was salinized, and yields were only slightly decreased when twothirds of the root system was salin ized. Excessive salinization of the surface soil did not affect water uptake. Water uptake by tomatoes was more affected by zonal salinization than was corn.

The Tomato Crop

“…Growing tomato plants in nutrient solutions with an osmotic potential of -600 KPa for short periods decreased both the_ osmotic potential and the water content of their leaves. A reduction of the leaf osmotic potential in response to a drop of the external osmotic potential has also been observed in other studies (Cram, 1976;Lunin and Gallatin, 1965). Exposure to osmotic stress reduced the osmotic potential of the cell to -1400 KPa compared with -800 in the controls .…”

Salt accumulation and distribution in a greenhouse soil as affected by salinity of irrigation water and leaching management

“…Investigators have reported that reduced plant water uptake from a zone of high salinity is by an increase in the uptake from a zone low in salinity (Lunin & Gallantin, 1965;Shalhevet & Bernstein, 1968). Although this takes place without significant reduction in yield, there is a general concern about how much salt can be stored in the root zone before leaching is needed (Hoffman, 1990).…”

Leaf Water Potential of Differentially Salinized Plants

“…There are relatively few reported experinments oni water uptake by l)lant root systemiis growing under a nonuniform-i distribution of salt concentration (4,9,10). It is known that when saline conditions vary with depth, water extraction is niot uniform with depth (11).…”