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Haijie Dou, Genhua Niu, Mengmeng Gu, and Joseph Masabni

photosynthesis in lower plant canopy levels and subsequently increase plant yield at the whole plant canopy level ( Dou et al., 2019a ; Terashima et al., 2009 ; Wang and Folta, 2013 ). In addition, G wavelengths induce shade avoidance responses in plants, such

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Rebecca M. Harbut, J. Alan Sullivan, John T.A. Proctor, and Harry J. Swartz

photosynthesis ( Zelitch, 1982 ). The increases in yield over the last century have been largely the result of increases in harvest index and light interception; however, the role that photosynthesis has played is not completely understood ( Richards, 2000 ). In

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Christopher J. Currey and Roberto G. Lopez

of cuttings declines after severance ( Veierskov, 1988 ). Although photosynthesis and carbohydrate production and storage are influenced by several biotic and abiotic factors such as carbon dioxide, temperature, nutrition, and water status, light is a

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Wenjie Ma, Wen Liang, and Bing Zhao

environment) ( Fanourakis et al., 2016 ). Research has shown that VPD not only has a direct effect on stomatal conductance ( g s ), photosynthesis, and water transport ( Sinclair et al., 2007 ) but also affects plant temperature via transpiration. Greater VPD

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Marc W. van Iersel and Bruce Bugbee

Dibutylurea (DBU), a breakdown product of benomyl, may be partially responsible for the previously reported phytotoxicity of the fungicide Benlate DF. We quantified the effect of DBU on the growth of two popular bedding plant species, petunia (Petunia × hybrida) and impatiens (Impatiens wallerana Hook. f.). DBU reduced photosynthesis of both species, and its effect strongly depended on the amount of DBU applied. The effects of DBU were most apparent 2 to 4 days after treatment, at which time 1.20 g·m-2 (corresponding to 10% DBU in Benlate DF at maximum labeled drench rate) inhibited photosynthesis completely. DBU also decreased flower number and caused marginal necrosis. DBU effects were more pronounced in low relative humidity. Benlate DF containing 3.1% DBU and an equivalent amount of reagent grade DBU had similar effects on photosynthesis and petunia necrosis. Our results showed that DBU is responsible for at least part of the phytotoxic symptoms that can be caused by Benlate DF. However, other ingredients or breakdown products may also contribute to the phytotoxic symptoms of Benlate DF.

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Dawei Shi, Xiaodong Wei, Guoxiang Chen, and Yanli Xu

Leaf senescence is characterized by programmed degradation of cellular constituents such as proteins, nucleic acids, and lipids, together with organelles and structures of leaf cell, resulting in a significant photosynthetic decline. Photosynthesis

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Ming Liu, Aijun Zhang, Xiaoguang Chen, Rong Jin, Hongmin Li, and Zhonghou Tang

exchange and chlorophyll fluorescence parameters were measured using a portable photosynthesis system (LI-6400 XT, LI-COR, Inc., Lincoln, NE). The P n , T r , g S , and intercellular CO 2 concentration ( C i ) were measured on the upper, third fully

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Vincent Pelletier, Steeve Pepin, Thomas Laurent, Jacques Gallichand, and Jean Caron

·ha −1 in 2014) ( APCQ, 2015 ). A decline in photosynthesis is one of the first physiological responses to soil waterlogging ( Liao and Lin, 2001 ). Poor aeration in the root zone generally leads to a reduction in root cellular respiration and

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Ajmer S. Bhagsari and Doyle A. Ashley

Field experiments with 15 sweet potato [Ipomoea batatas L. (Lam.)] genotypes were conducted to study the physiological basis of yield in 1981 and 1982. The leaf area index differed significantly among the sweet potato genotypes during early and late phases of growth, hut showed an inconsistent relationship with yield. Single leaf net photosynthesis ranged from 0.74 to 1.12 mg CO2/m' per sec. Canopy photosynthesis for sweet potato genotypes differed significantly in 1981, but not in 1982. It ranged from 0.81 to 1.16 mg CO2/m2 per sec in Aug. 1981. and from 0.63 to 0.88 mg CO2/m2 per sec in 1982. Four hours after “C-labeling, 14C-assimilate translocation from the treated leaf ranged from 21% to 46%, but did not differ significantly among the genotypes. At final harvest, harvest index [HI, defined as (storage root yield/total biological yield) × 100] of the genotypes varied from 43% to 77% and 31% to 75% for 1981 and 1982, respectively. Canopy photosynthesis during September was significantly correlated with storage root dry matter yield (r = 0.54*) in 1981 and with phytomass (above-ground biomass plus storage roots) (r = 0.60*) in 1982. Both phytomass and HI were significantly correlated with storage root matter yield. Canopy photosynthetic evaluation of sweet potato germplasm may be-more relevant when the storage root sinks are at an advanced stage of development. Our study suggests that yield is poorly predicted by Pn, particularly when the genotypes have different leaf sizes.

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Carole L. Bassett and D. Michael Glenn

Light perception in plants is critical to their survival because light regulates three important processes: skotomorphogenesis, photomorphogenesis, and photosynthesis. At ground level the composition of sunlight is ≈3% ultraviolet, 44% visible (380