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Root Temperature and Calcium Level Effects on Winter Wheat Forage: I. Shoot and Root Growth

Univ. Hawaii Branch Stn., 461 W. Lanikaula St. Hilo, HI 96720
U.S. Plant, Soil & Nutrition Lab., Tower Road, Ithaca, NY 14853.

^* Corresponding author.

Wheat pasture poisoning is a metabolic disorder of ruminants, that occurs particularly in the spring, during a sudden spurt in plant growth, under conditions of optimum temperature, ample soil moisture and adequate mineral supply. To determine the effects of an increase in root temperature and four Ca levels on the shoot and root growth of winter wheat (Triticum aestivum L. ‘Centurk’), seedlings were grown under three root temperature regimes (constant 8 °C, constant 16 °C, and increasing from 8-16 °C), in nutrient solutions with four Ca levels (0.2,0.6,2.0, and 5.0 mM). No significant differences due to Ca levels were found for growth rates of the shoots and roots (dry weight basis), nor for root extension rates. Growth rates of the shoots and roots (dry weight basis), and root extension rates were significantly slower for plants grown at 8 °C compared to those grown at 16 °C. Lateral root growth, in particular, was depressed in plants grown at a cold root temperature. The mean root diameter was significantly greater at 8 °C than at 16 °C, apparently due to the greater proportion of main root axes with larger root diameters at a cold root temperature. Plants transferred to 16 °had growth rates of the shoots and roots that were intermediate, relative to those grown at constant low or constant high root temperatures. A lag period of 1 wk was observed before shoot and root dry weights of plants transferred to 16 °C increased, compared to those maintained at 8 °C. Thus, root temperatures play a major role in modifying shoot and root growth parameters.

Received for publication October 24, 1988.