Leaf stomatal conductance (gs), transpiration rate (E), and light-saturated net photosynthetic rate (PNmax) at three developmental stages (tillering stage, jointing-booting stage, and milking stage) and leaf total nitrogen concentration (LTNC) and δ13C value at milking stage were measured for a conventional rice line (Minghui 63) and its corresponding Bacillus thuringiensis (Bt)-gene [cry1A
(b and c)] introduced line (Bt line) under three fertilizer levels. Compared to conventional line, Bt line showed lower gs, which was associated with lower P Nmax and E, but instantaneous water-use efficiency (WUE), measured as the ratio of PNmax to E, was higher in the Bt line than in the conventional line, particularly in the jointing-booting stage. However, δ13C values were not significantly different across treatments, suggesting that intrinsic water-use efficiency (WUEin) might be indistinguishable between Bt and conventional lines. LTNC was higher but PNmax was lower in Bt line compared to conventional line, resulting in significantly lower photosynthetic nitrogen-use efficiency (PNUE). This might result from the additional cost of producing Bt protein in the Bt line due to the effect of competing nitrogen with photosynthetic machinery. Bt-gene introduction and expression does not significantly change WUEin but may significantly decrease leaf PNUE. Thus we suggest that Bt rice should be carefully examined in relation to environmental risks (e.g. water-body pollution) before planting commercially. and R. Q. Guo ... [et al.].
Water and nitrogen (N) deficiency are two major constraints limiting the yield and quality of many oilseed crops worldwide. This study was designed to assess the response of Camelina sativa (L.) Crantz to the availability of N and water resources on photosynthesis and yield parameters. All the measured variables, which included plant height, root and shoot dry matter, root:shoot ratio, xylem pressure potential (XPP), yield components, photosynthetic parameters, and instantaneous water-use efficiency (WUE) were remarkably influenced by water and nitrogen supply. Net photosynthetic rate (PN) and yield components were significantly decreased more by water deficit than by N deficiency. XPP, stomatal conductance (gs), and intercellular CO2 concentration (C i) decreased substantially as the water deficit increased irrespective of the level of N application. WUE at the high N supply [100 and 150 kg(N) ha-1] dropped in a large degree as the increased water deficit due to a larger decrease in PN than transpiration rate (E). The results of this study suggest that the regulative capacity of N supply on photosynthetic and plant growth response is significantly affected by soil water status and C. sativa is more sensitive to water deficit than N supply. and X. Pan ... [et al.].
Effects of water and nitrogen (N) supply on growth and photosynthetic response of B. carinata were examined in this study. Plant growth and related characteristics varied significantly in response to the availability of water and nitrogen. B. carinata maximized the utilization efficiency of the most limiting resources by developing physiological adaptations, such as changes in root and leaf development. The utilization of water and N was tightly linked with the availability of each resource. Instantaneous water-use efficiency (WUE) was always greater in plants with high-N nutrition [50, 100, and 150 kg(N) ha-1] than in the low-N-treated plants
[0 kg(N) ha-1] in all watering treatments. Instantaneous N-use efficiency (PNUE) decreased significantly with increasing water stress in all N treatments. Seed yield is significantly related to PNUE (p>0.05) but not WUE (p<0.05). The positive relationship between leaf net photosynthetic rate (PN) and seed yield suggests that PN can be used as an important tool for selection of new strains with high seed yield. and X. Pan ... [et al.].