Morphology and Physiology of Re-growth of the Tropical Tallgrass Hybrid Pennisetum

Changes in d. wt and ¹⁴C distribution were followed in individualorgans during re-growth of hybrid pennisetum after exposureof the plants to [¹⁴C]carbon dioxide before or after defoliation.The changes were recorded at three temperatures (18/13, 24/19and 30/25 °C day/night) in plants in which the apical meristemhad been left intact or removed at defoliation. Initial re-growth was more rapid and at the expense of stemd. wt losses where the apical meristem had been left intact.Rapid re-growth was associated with breakdown of organic reserves(proteins and polysaccharides) and with the capturing of one-quarterof the net ¹⁴C lost from the whole plant. In decapitated plantsre-growth was delayed until new tillers developed and was rapidthereafter. The pattern of photosynthate mobilization was notaffected by temperature, but the speed of mobilization increasedmarkedly with temperature. The pattern was much the same forphotosynthate fixed before or after defoliation, but a highproportion of the ¹⁴C fixed after defoliation was respired andonly 5 per cent entered subsequent new growth. Pennisetum hybrid, tallgrass, re-growth     

Primary Growth and Re-growth of the Tropical Tallgrass Hybrid Pennisetum at Different Temperatures

Dry weight of plant fractions, leaf area, leaf number and tillernumber were recorded throughout primary growth and two subsequentre-growths of hybrid Pennisetum (Pennisetum americanum x P.purpureum) at five temperature regimes from 15/10 °C to33/28 °C (day/night) in summer and winter. Seedling mortality occurred at 15/10 °C, whereas at allhigher temperatures seedlings survived and plants re-grew aftercutting at a height of 10 cm. Shoot weights increased with temperatureup to 33/28 °C when compared at a common chronological agebut showed no differences at a common developmental age. Thetemperature response was associated with increased top/rootratio and rate of leaf appearance; mean individual leaf areaand NAR did not increase beyond 27/22 °C. Shoot weight incrementsin primary growth were the same in winter and summer when expressedper unit of radiation, although leaf area per unit weight wassensitive to changes in radiation associated with differencesin daylength. The rate of shoot weight accumulation in regrowthwas greater than in primary growth because of rapid tilleringfollowing defoliation and an enhanced rate of leaf appearanceper tiller. Pennisetum hybrid, tallgrass, growth, regrowth temperature response     

The Effect of Temperature on Growth and Development of Echinochloa Millets

Accumulation of dry weight and leaf plus stem area were measuredin Echinochloa utilis and E. frumentacea grown at temperatureregimes from 15/10°C to 33/28°C (day/night). Tilleringand height were recorded in addition to leaf number which wassubsequently used as a developmental index. In both species shoot dry weight increased with temperatureup to 33/28°C; the increase in relative growth rate (RGR)was negligible above 27/22°C. Below 27/22°C the RGRof E. frumentacea decreased sharply and at 15/10°C it madeno effective growth. At low temperatures the RGR of E. frumentaceawas lower than that of E. utilis due to slow leaf area expansion,and in particular smaller individual leaves. E. frumentaceatillered more than E. utilis. Plant development was retardedat low temperatures but was not as responsive to temperatureas dry weight and leaf area. The different responses to temperatureof the two species were described in equations suitable forinclusion in predictive growth models. Echinochloa spp., millet, growth, development, temperature, relative growth rate