XIN KEY MATLAB 2012 HOW TO

curvature factors, need to be modified dependent on the leaf area index (LAI), leaf nitrogen content and the proportion of diffuse light ( de Pury and Farquhar 1997). This improves the prediction accuracy of the big-leaf models however, it renders big-leaf models essentially unscaleable in the sense that these parameters, e.g. the curvature factor вЂ“ can be adjusted in the big leaf model. 1995) and the smoothness of the transition from light-limited to light-saturated photosynthesis ( Sellers et al. Given this inaccuracy, some model parameters вЂ“ namely the photosynthetic capacity ( Lloyd et al. Such heterogeneities are ignored in current big-leaf, sunlitвЂ“shaded and multilayer models. However, inside a canopy, the light distribution is highly heterogeneous both spatially and temporarily, mostly due to the heterogeneity of leaf angles and the sunflecks deep in the canopy ( de Pury and Farquhar 1997). This principle was extended to the canopy and formed the basis for the big-leaf canopy photosynthesis models. Farquhar ( Farquhar 1989) demonstrated that equations describing leaf photosynthesis are the same as those for chloroplast photosynthesis as long as (a) the chloroplast photosynthetic capacity is proportional to the irradiance it absorbs and (b) the responses of the photosynthetic CO 2 uptake to irradiance are identical among different chloroplasts. The big-leaf model assumes that the leaf nitrogen is optimally distributed to match the light environments inside a canopy ( Sellers et al. 2004) ( iii) and the multi-layer model ( deWit 1965 Duncan et al. 1995) ( ii) the sunlitвЂ“shaded model ( de Pury and Farquhar 1997 Wang and Leuning 1998 Dai et al. 1992 Amthor 1994 Kull and Jarvis 1995 Lloyd et al. Depending on the level of complexity, these models can be roughly divided into three categories: ( i) the big-leaf model ( Running and Coughlan 1988 Thornley and Johnson 1990 Sellers et al. Many canopy photosynthesis models with different levels of details have been developed to date.

Given the logistic difficulty of estimating canopy photosynthesis in the field, mathematical modelling has typically been used to estimate A c. This is a challenge, partially due to the lack of efficient methods to measure A c, although many efforts have been devoted to developing canopy photosynthesis chambers ( Reicosky and Peters 1977 Steduto et al.

XIN KEY MATLAB 2012 HOW TO

The challenge now is how to identify the ideal canopy architectural and leaf metabolic features to breed or engineer for increased canopy photosynthesis for current, and more importantly, for future elevated CO 2 conditions. Though there is still some controversy regarding whether improving photosynthesis can lead to increased crop yields, this may be more related to using leaf rather than canopy photosynthesis in deriving the relationship ( Zelitch 1982). In particular, selection of cultivars with more erect leaves, especially at the top of the canopy, has led to improved light environments inside a canopy and hence, improved canopy photosynthetic CO 2 uptake rate ( A c) ( Long et al. One of the major mechanisms underlying the improved crop yields during the вЂgreen revolutionвЂ™ has been improved canopy architectures. 2010), since canopy rather than leaf photosynthesis is closely related to crop yields. Improving photosynthetic capacity is one of the main approaches to further enhance crop productivity ( Long et al.

A close linkage between canopy photosynthesis modelling and canopy photosynthesis measurements is required to fully realise the potential of such modelling approaches in guiding crop improvements. This model provides a framework for designing ideal crop architectures to gain optimal A c under future changing climate conditions. Simulation results suggest that to gain an optimal A c for the examined rice cultivar, the stem height, leaf width and leaf angles can be manipulated to enhance canopy photosynthesis. We also evaluated theoretically the influence of canopy architectural on A c under current and future C a in rice. With this model, we demonstrated that the A c estimated from вЂaverageвЂ™ canopy light conditions is ~25% higher than that from light conditions at individual points in the canopy. To study this question, we developed a new model of canopy photosynthesis, which includes three components: ( i) a canopy architectural model ( ii) a forward ray tracing algorithm and ( iii) a steady-state biochemical model of C 3 photosynthesis. Whether crop architectures in current elite crop cultivars can be modified for increased canopy CO 2 uptake rate ( A c) under elevated atmospheric CO 2 concentrations ( C a) is currently unknown.

Canopy architecture has been a major target in crop breeding for improved yields.

Xin key matlab 2012