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Ji Jhong Chen, Yuxiang Wang, Asmita Paudel, and Youping Sun

reduces photosynthesis ( Taiz et al., 2015 ). Fig. 3. Net photosynthesis rate [carbon dioxide (CO 2 ) (A)] and transpiration rate [water (H 2 O) (B)] of rose of sharon, ninebark, and japanese spirea irrigated for 11 weeks with saline solutions at eight

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Youping Sun, Genhua Niu, and Christina Perez

transpiration of ‘Texas Pink’ phlox plant in EC 5 and EC 10 was 30% and 75% lower than that in the control, respectively. Table 3. Leaf transpiration (E), stomatal conductance ( g S ), and net photosynthesis (P n ) of Texas Superstar ® perennials irrigated with

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Julián Miralles-Crespo and Marc W. van Iersel

conductance ( g S ), net photosynthesis (P n ), instantaneous water use efficiency (WUE i ), area of the fully expanded leaves, and shoot dry weight (DW) of Begonia semperflorens after 2 months of irrigation using an Acclima CS3500 irrigation controller

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Jean-Pierre Privé, Lindsay Russell, and Anita LeBlanc

net photosynthesis (Pn) were achieved at a higher frequency of kaolin particle film application and that this was particularly the case at leaf temperatures exceeding 35 °C ( Privé et al., 2007 ). Ultraviolet damage and photoinhibition can be additive

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Shannon Rauter, Youping Sun, and Melanie Stock

). Gas exchange measurements were collected at the end of the experiment for all living plants using a portable photosynthesis system (LI-6800; LI-COR Biosciences, Lincoln, NE). After taking all measurements, all plants were harvested and placed in a

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

were observed, which were lower than the basil grown under DLIs of 28.8 and 34.6 mol·m −2 ·d −1 in a growth chamber, respectively ( Beaman et al., 2009 ). In a glasshouse condition, there was no difference in photosynthesis of ‘Genovese’ basil between

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Yuxiang Wang, Youping Sun, Genhua Niu, Chaoyi Deng, Yi Wang, and Jorge Gardea-Torresdey

(EC e ), plant visual score, height, leaf area, number of inflorescences, number of tillers, shoot dry weight (DW), relative chlorophyll content [soil–plant analysis development (SPAD) reading], net photosynthesis rate (P n ), stomatal conductance ( g

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D. Schwarz, H.-P. Kläring, M.W. van Iersel, and K.T. Ingram

An increase in nutrient solution concentration to produce high-quality fruit vegetables, such as tomatoes, may reduce growth and yield. One reason might be inhibition of photosynthesis, but results of photosynthesis studies in the literature are inconsistent. In this study, we investigated growth and photosynthesis of whole `Celebrity' and `Counter' tomato [Lycopersicon esculentum (L.) Mill.] plants in response to nutrient solution concentration, measured as electrical conductivity (EC). The effects of two levels of photosynthetic photon flux density (PPF = 400 or 625 μmol·m-2·s-1) on plant response to nutrient solution EC in a range between 1.25 to 8.75 dS·m-1 in a series of four experiments in gas exchange chambers placed in larger growth chambers were examined. Increasing PPF enhanced tomato growth and photosynthesis but increasing EC diminished them. Reduction of dry weight was 1.9% to 7.3%, while plant photosynthesis was reduced between 1.7% and 4.5% for each 1 dS·m-1. Increasing EC did not decrease dry matter content and leaf photosynthesis. Mean plant dry matter content ranged between 70 and 95 g·kg-1, and net leaf photosynthesis on the last measurement day was between 7.5 and 11.3 μmol·m-2·s-1, depending on experiment. The decrease in whole plant photosynthesis with an increase in EC was caused by decreased leaf area but not by a decrease in leaf photosynthesis.

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J.S. Seron, R.J. Ferree, S.L. Knight, M.A.L. Smith, and L.A. Spomer

Tolerance of increased salinity by tomato is of great importance to the tomato processing industry, where increased conductivity of up to 6 dS m-1 is used to increase specific yield components. A new line of miniature dwarf tomato, Lycopersicon esculentum Mill. cv. Micro Tom, was evaluated for photosynthetic response to elevated salinity. Tomatoes were grown in solution batch culture and subjected to constant salt treatments of 2.4 (control), 7.6, 12.8, or 18 dS m-1. Weekly photosynthetic measurements were made beginning week 4 on the most recent fully open leaf or leaf opposite a fruit. Net photosynthesis decreased across all salt treatments over the last six weeks of sampling. As salinity level increased, net photosynthesis decreased compared to the control. The 18 dS m-1 treatment reduced net photosynthesis relative to 12.8 and 7.6 dS m-1. Although salinity increased succulence, limitations to net photosynthesis were due to diminished utilization of intercellular CO2, rather than reduced internal CO2 concentration or stomatal conductance.

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Stephanie E. Burnett, Marc W. van Iersel, and Paul A. Thomas

French marigold (Tagetes patula L. `Boy Orange') was grown in a peat-based growing medium containing different rates (0, 15, 20, 30, 42, or 50 g·L–1) of polyethylene glycol 8000 (PEG-8000) to determine if PEG-8000 would reduce seedling height. Only 28% to 55% of seedlings treated with 62, 72, or 83 g·L–1 of PEG-8000 survived, and these treatments would be commercially unacceptable. Marigolds treated with the remaining concentrations of PEG-8000 had shorter hypocotyls, and were up to 38% shorter than nontreated controls at harvest. Marigold cotyledon water (ψw), osmotic (ψs), and turgor (ψp) potentials were significantly reduced by PEG-8000, and ψp was close to zero for all PEG-treated seedlings 18 days after seeding. Whole-plant net photosynthesis, whole-plant dark respiration, and net photosynthesis/leaf area ratios were reduced by PEG-8000, while specific respiration of seedlings treated with PEG-8000 increased. Marigolds treated with concentrations greater than 30 g·L–1 of PEG-8000 had net photosynthesis rates that were close to zero. Fourteen days after transplanting, PEG-treated marigolds were still shorter than nontreated seedlings and they flowered up to 5 days later. Concentrations of PEG from 15 to 30 g·L–1 reduced elongation of marigold seedlings without negatively affecting germination, survival, or plant quality. It appears that marigold seedlings were shorter because of reduced leaf ψp and reductions in net photosynthesis.