Growth rates, harvest index and moisture use of manitou spring wheat as influenced by nitrogen, temperature and moisture

Manitou spring wheat (Triticum aestivum L.) was grown at combinations of three day/night temperatures (27/12 °C (T27), 22/12 °C (T22) and 17/12 °C (T17)), three levels of fertilizer N (58, 116 and 174 kg/ha), and three moisture stresses (nominally −0.03, −1.5 and −4.0 MPa) applied for four durations (viz., no stress throughout, stress from (i) four-tiller (Tg), (ii) near ligule of last leaf visible (LLV), or (iii) flowering (F1) stages to harvest (Hvst)). Weights of plant parts and photosynthetic area of leaves and stems were measured at eight growth stages. Mean net rate of photosynthesis was estimated by dividing plant dry weight by photosynthetic area duration. Temperature was the main factor affecting net photosynthesis and growth. Under optimum moisture and fertility, net photosynthesis was inversely related to temperature being 1.15, 1.19 and 1.29 μg∙cm−2∙day−1 at T27, T22 and T17, respectively. However, absolute growth rates were highest at T22. For example, at low moisture stress and N174, absolut...