The effects of temperature on the early vegetative growth of Phalaris canariensis L. and P. tuberosa L.

Abstract

Seedlings of Phalaris canariensis and P. tuberosa were grown in pots outdoors and under glass-house conditions in experiments at Canberra.

Sigmoid curves expressed the increase in total dry weight, dry weight of plant parts, and tiller number for both species grown outdoors for 5 months. Phase 1 — the vegetative phase of growth — ended on about September 18 for P. canariensis and September 12 for P. tuberosa. Subsequent experiments were concerned with the effects of temperature on this growth phase.

In experiments lasting for up to 44 days, both species were grown under natural (winter) conditions of light intensity and day length (less than 12 hr) and 16 combinations of day and night temperature. The optimum regime for dry weight production — 24/18–19°C — did not correspond with that optimal for tiller initiation. Highest tiller numbers were obtained when night temperature exceeded day temperature (19/22° or 19/24°), or approached the optimum day temperature (24/22° or 24/24°), or there was a relatively large fluctuation between day and night temperature (28/18°, for example). P. canariensis outyielded P. tuberosa under optimum temperature conditions, but P. tuberosa appeared to be less sensitive to night temperatures of 22–24°. No consistent trends in the effects of day or night temperature on the nitrogen content of tops, leaf length, leaf breadth, or the ratio leaf length/breadth were obtained. Leaf size and shape were, however, influenced by temperature.

A comparison of the growth of the Australian commercial P. tuberosa was made with that of strains from Israel and Algeria under six temperature regimes. Under cold and cool conditions, the Algerian strain resembled the Australian strain, both being outyielded by the Israeli strain. Under a regime of 28/23°, however, the Algerian and Israeli strains were adversely affected, the latter more than the former.

In nutrient culture solution, a root temperature of 20° approached the optimum for dry weight production and tiller initiation by P. canariensis more nearly than one of either 12° or 27°, ambient temperature being 24/20°. Leaf size was also influenced by root temperature.