Interactions Between Rising CO2 Concentration and Nitrogen Supply in Cotton. I. Growth and Leaf Nitrogen Concentration
Australian Journal of Plant Physiology
23(2) 119 - 125
The influence of sink development on the response of shoot growth in cotton (Gossypium hirsutum L. cv. Siokra BT1-4) was investigated by growing plants at three levels of CO2=2 concentration: 350 (ambient), 550 and 900 μL L-1 and six levels of nitrogen (N) supply ranging from deficient to excess (0-133 mg N kg-1 soil week-1). Changes in leaf N concentration were also investigated. At 59 days after sowing, there was an average 63% increase in shoot growth at 550 μL CO2 L-1 compared with ambient CO2-grown plants, with no significant growth increase at 900 μL CO2 L-1 and, this response was closely matched by sink development (flower number and stem weight). Low N supply restricted the responses of both sink development and shoot growth to high CO2. At elevated CO2, leaf N concentration was reduced by an average 27% at low to adequate N supply. The high CO2-induced reduction in leaf N concentration, however, disappeared when the N supply was increased to a high level of 133 mg N kg-1 soil week-1. These CO2 effects on leaf N concentration were smaller when N was expressed per unit leaf area, apparently due to a combination of the effects of elevated CO2 or high N supply reducing specific leaf area and, to an N uptake limitation at low to moderate levels of N supply. The critical foliar N concentrations (leaf N concentration at 90% of maximum shoot growth) were reduced from 42 to 38 and 36 mg g-1 when CO2 concentrations were increased from 350 to 550 and 900 μL L-1 respectively, indicating that changes in fertiliser management may be required under changing CO2 concentrations.
© CSIRO 1996