Photosynthetic light responses of apple (Malus domestica) leaves in relation to leaf temperature, CO2 and leaf nitrogen on trees grown in orchard conditions

2018 ◽  
Vol 45 (11) ◽  
pp. 1149 ◽  
Author(s):  
Dennis H. Greer

Apple trees growing in orchard conditions with two levels of soil nitrogen were used to determine photosynthetic light responses in relation to leaf temperature. In addition, leaves growing along the shoot were measured, and substrate supply for photosynthesis manipulated by altering CO2 concentrations. Results indicated highly significant interactions between leaf temperature, CO2 concentration, leaf position and nitrogen concentrations on attributes of the photosynthetic light responses. Elevated CO2 enhanced the effect of leaf temperature on the light saturated rate (Amax). There were significant effects of leaf position, and apparent photon yield (quantum efficiency) of photosynthesis, Amax and photosynthetic nitrogen use efficiency (ANUE) increased along the shoot, from leaves at the shoot base to those at apical positions; elevated CO2 enhanced these differences. A similar trend occurred with leaf nitrogen, accounting for increases in the photon yield, Amax and ANUE. It was concluded that apical leaves may have accumulated nitrogen which caused the high photosynthetic capacity and nitrogen use efficiency, as these leaves were possibly most exposed. Basal leaves, being possibly exposed to lower light intensities, had low nitrogen concentrations which accounted for their low photosynthetic light responses. This study does demonstrate that the shoot position of the apple leaves had marked effects on the photosynthetic light response and these were correlated with the leaf nitrogen content.

2007 ◽  
Vol 27 (8) ◽  
pp. 1153-1163 ◽  
Author(s):  
C. Calfapietra ◽  
P. d. Angelis ◽  
B. Gielen ◽  
M. Lukac ◽  
M. C. Moscatelli ◽  
...  

2015 ◽  
Vol 29 ◽  
pp. 109-110
Author(s):  
Helale Bahrami ◽  
Roger Armstrong ◽  
Glenn J. Fitzgerald ◽  
Michael Tausz ◽  
Sabine Tausz-Posch

2016 ◽  
Vol 43 (9) ◽  
pp. 862 ◽  
Author(s):  
José L. Rotundo ◽  
Lucas Borrás

Soybean has a narrow genetic base thought to limit future yield genetic gains. However, there is no evidence whether this reduction in genetic diversity correlates with diversity loss for any yield trait. We tested how photosynthetic nitrogen use efficiency (leaf photosynthesis per unit nitrogen, NUEp) evolved from the wild relative Glycine soja Siebold & Zucc. to the current Glycine max (L.) Merr. Five populations resulting from different evolutionary bottlenecks were evaluated under field conditions. Populations were wild ancestors, domesticated Asian landraces, North American ancestors, and modern cultivars. Genotypic differences in photosynthesis and leaf nitrogen were evident, creating a significant 3-fold variation in phenotypic NUEp. There was a parallel reduction in molecular marker and phenotypic NUEp diversity after each evolutionary bottleneck. G. soja had three times more NUEp diversity and 25% more average NUEp compared with the elite modern cultivars. Two strategies for increasing NUEp were identified: (i) increases in light saturated photosynthesis (Pmax), and, alternatively, (ii) reductions in leaf nitrogen. A modelling approach showed that NUEp will increase yield only if based on increased Pmax. Our study quantified the genetic potential of exotic germplasm available for trait-directed breeding. Results antagonise the concept that elite germplasm is always superior for any relevant yield trait when compared with undomesticated germplasm.


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