Abstract
AbstractIncreasing nitrogen use efficiency is a key target for yield improvement programs. Here we identify features of rice canopy architecture during altered N availability and link them to photosynthetic productivity. Empirical mathematical modelling, high-resolution 3-dimensional (3D) reconstruction and gas exchange measurements were employed to investigate the effect of a mild N deficiency vs. surplus N application on canopy architecture, light and photosynthesis distribution throughout development. Three contrasting rice lines: two Malaysian rice varieties (MR219 and MR253) and a high-yielding indica cultivar (IR64) were cultivated. 3D reconstruction indicated key N-dependent differences in plant architecture and canopy light distribution including changes to leaf area index (LAI), tiller number, leaf angle and modelled light extinction coefficients. Measured leaf photosynthetic capacity did not differ substantially between the high and reduced N treatments; however, modelled canopy photosynthesis rate indicated a higher carbon gain per unit leaf area for the reduced N treatment but a higher carbon gain per unit ground area for the high N treatment. This is a result of altered canopy structure leading to increased light distribution under reduced N which partially offsets the reduced LAI. Within rice, altered N availability results in the development of full photosynthetically functional leaves, but leads to altered canopy architecture, light distribution and overall productivity suggested that N availability can be fine-tuned to optimize biomass production. We propose wider use of 3D reconstruction to assess canopy architecture and productivity under differing N availabilities for a range of species.
Highlights
Increased crop yield per hectare will be needed to sustain the growing global population. yield barriers are imposed by the decreasing availability of land and resources combined with a rapidly changing climate (Ray et al, 2012; Challinor et al, 2014)
The canopy reconstructions for each treatment for each of the five growth stages during development are provided as a visual representation in Figure 1, where GS5 indicates full canopy closure and GS1-4 represent vegetative stages two weeks apart starting 18 days after transplanting (DAT)
Visual differences can be discerned between the lines and between treatments e.g. all lines show a greater amount of plant material under the high N treatment relative to the low N treatment and this is apparent at all stages
Summary
Increased crop yield per hectare will be needed to sustain the growing global population. yield barriers are imposed by the decreasing availability of land and resources combined with a rapidly changing climate (Ray et al, 2012; Challinor et al, 2014). Increased crop yield per hectare will be needed to sustain the growing global population. Is one of the most costly agricultural inputs, in terms of finance and environmental impact, despite being one of the most important mineral nutrients required to sustain yields. Field grown crops require an external input of N as fertiliser but strategies for application vary substantially (Peng et al, 2006; Peng et al, 2010). Large amounts of N fertilisers are used to increase yield and to prevent fluctuating resources from affecting production (Kant et al, 2011), growing concerns over the environmental consequences of mineral N use, and its potential contamination when not used efficiently, has led to the need for research in the interactions between availability and crop growth (Peng et al, 2010).
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