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Robert A. Kennedy, Theodore C. Fox, and Wayne H. Loescher

Abstract

The rate and efficiency of photosynthesis (PS) is unquestionably one of the primary determinants of crop yield. Yet, as this symposium illustrates, many other factors contribute to plant productivity. Indeed, the exact relationship between PS rate and yield remains undefined. For several years we have now been interested in factors that affect PS rate in both C3 and C4 plants, not only within the plant, but also external to it. Internal factors affecting PS that will be discussed include leaf age, leaf canopy, photorespiration, stage of plant development (including both vegetative and reproductive phases), and the occurrence of little-recognized metabolic pathways such as polyol synthesis and transport. External factors that affect PS, in addition to obvious environmental determinants such as temperature, light, and water, include the seasonal growth cycle. While we still do not understand how all of these factors interact to affect yield, we are beginning to understand their singular effects. Control of these factors, once thought to be within reach even before the advent of biotechnology, remains likely, but distant.

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Tessa M. Mills, Jianming Li, and M. Hossein Behboudian

. Photosynthetic rate (Pn), g s , internal leaf CO 2 concentrations (C i ), and leaf temperature were determined on young but fully expanded leaves using a photosynthesis measurement system (LI-6400; LI-COR, Lincoln, NE). Photosynthetically active radiation ( PAR

Open access

Liang Zheng, Qi Zhang, Kexin Zheng, Shumei Zhao, Pingzhi Wang, Jieyu Cheng, Xuesong Zhang, and Xiaowen Chen

depths with three replicates. The measurement positions were adjusted with the growth of the plants ( Fig. 2 ). The temperature was measured from 5 June 2017 to 10 July 2017. Measurements of leaf photosynthesis and solar radiation transmittance. The P n

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Toshio Shibuya, Ryosuke Endo, Yoshiaki Kitaya, and Saki Hayashi

. Contradictory results have been reported for NAR. Heraut-Bron et al. (1999) demonstrated that the R:FR did not affect photosynthesis per unit leaf area of white clover ( Trifolium repens L.). However, other reports demonstrated that low-R:FR light reduces the

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Patrick Burgess and Bingru Huang

stresses ( Burgess and Huang, 2014 ; Ferreira et al., 2006 ; Huang et al., 2014 ; Jespersen et al., 2015 ; Kosová et al., 2011 ; Merewitz et al., 2011 ). In response to drought stress alone, the abundance of proteins involved in photosynthesis

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S. Kumudini

Cranberry [Vaccinium macrocarpon (Ait.)] yield has been associated with photosynthate supply. However, the impact of temperature and radiation on photosynthesis of the cranberry plant is not well understood. The objective of this experiment was to characterize the photosynthetic response to radiation and temperature in order to develop a model for estimation of cranberry photosynthetic rates. Two cranberry cultivars, `Stevens' and `Ben Lear', were tested for photosynthetic response at air temperatures ranging from 15 to 35 °C and radiation intensities from 200 to 1200 μmol·m-2·s-1. Depending on temperature, maximum photosynthesis (Pmax) was ≈10 or 12 μmol CO2/m2/s (net photosynthesis) and the saturating radiation level was estimated to be 600 to 800 μmol·m-2·s-1. Cranberry quantum yield was estimated as 0.03 mol CO2/mol photon. Both models; Blackman and the nonrectangular hyperbola with a Θ (angle of curvature) of 0.99 were a good fit for measured photosynthetic rates under controlled environment conditions. The disparity between modeled predicted values, and observed values in the field around midday, indicates a reduction in potential photosynthetic rates in a diurnal cycle that is consistent with the phenomenon of midday depression.

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Paul Deram, Mark G. Lefsrud, and Valérie Orsat

electrical conversion efficiency ( Gomez et al., 2013 ). HPS lamps were tailored for human vision and therefore are not ideally suited for plant growth ( Bula et al., 1991 ). Earlier research has shown that the most important wavelengths for photosynthesis

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Xing-Zheng Fu, Fei Xing, Li Cao, Chang-Pin Chun, Li-Li Ling, Cai-Lun Jiang, and Liang-Zhi Peng

and g s , resulting in reduction of photosynthesis ( Sharma et al., 1995 ). Application of the three Zn fertilizers on Zn-deficient leaves significantly increased their chlorophyll levels and photosynthetic activities, especially when organosilicone

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Tessa Pocock

signaling networks involved. The photoreceptor (PR) network involves light absorption by phytochromes (PHY), cryptochromes (CRY) and the light oxygen voltage PRs, phototropin (PHO), and zeitlupe (ZTL). The photosynthesis (PSN) sensing and signaling network

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Krishna Nemali and Marc W. van Iersel

declines rapidly with small changes in substrate water content ( da Silva et al., 1993 ), making it more difficult for plants to extract water when Θ is low in the substrate. Photosynthesis is central to crop growth and highly sensitive to drought stress