Search Results

You are looking at 1 - 10 of 19 items for :

  • "quantum yield of photosystem II" x
Clear All
Restricted access

Shuyang Zhen and Marc W. van Iersel

dissipated as heat and a small fraction is re-emitted as chlorophyll fluorescence ( Maxwell and Johnson, 2000 ). The quantum yield of photosystem II, the efficiency with which photosystem II (PSII) uses absorbed photons for electron transport, or the moles of

Free access

Marc W. van Iersel, Geoffrey Weaver, Michael T. Martin, Rhuanito S. Ferrarezi, Erico Mattos and Mark Haidekker

(top) and a simplified diagram of the duty cycle control board (bottom). A fluorometer is used to measure the quantum yield of photosystem II and the datalogger calculates the electron transport rate from this and the photosynthetic photon flux density

Open access

Kaylee A. South, Paul A. Thomas, Marc W. van Iersel, Cindy Young and Michelle L. Jones

thermocouple was placed in the bark ≈5 cm below an aerial root. Temperature data were collected every 5 min for 3 h after an irrigation event. Quantum yield of photosystem II and chlorophyll content. At the beginning of the experiment, the newest-most fully

Restricted access

Geoffrey Weaver and Marc W. van Iersel

µmol·m –2 ·s –1 . Fig. 2. Quantum yield of photosystem II (Φ PSII ) of ‘Green Towers’ lettuce as a function of photosynthetic photon flux density ( PPFD ) based on 35 d of constant diurnal monitoring. Closed symbols represent measurements taken before

Restricted access

David H Suchoff, Christopher C. Gunter, Jonathan R. Schultheis, Matthew D. Kleinhenz and Frank J. Louws

fluorometer (LI-6400XT; LI-COR, Inc., Lincoln, NE). Net CO 2 assimilation ( A , µmol·m −2 ·s −1 ), g S (mmol·m −2 ·s −1 ), and effective quantum yield of photosystem II (φ PSII ) were measured between 10 am and 1 pm. Photosynthetic photon flux density

Free access

Toshio Shibuya, Ryosuke Endo, Yuki Kitamura, Yoshiaki Kitaya and Nobuaki Hayashi

under FL H or 6 d under ML, sample seedlings from each treatment group were taken to measure the net photosynthetic rate (P n ) and quantum yield of photosystem II photochemistry (Ф PSII ; Maxwell and Johnson, 2000 ). Because of the faster development

Free access

Jieshan Cheng, Peige Fan, Zhenchang Liang, Yanqiu Wang, Ning Niu, Weidong Li and Shaohua Li

bag removal” treatment at 1100 hr and 1000 to 1100 hr , respectively ( Fig. 2, E and F ). Fig. 2. Diurnal changes in ( A ) maximal quantum yield of photosystem II (F v /F m ), ( B ) actual photochemical efficiency of photosystem II (ΦPSII

Free access

S. Kalantari, G. Samson, J. Makhlouf and J. Arul

The application of ultraviolet light on fruit and vegetables is a promising new method to control storage diseases and to delay the onset of senescence. In this investigation, we studied the effects of hormic dose (1,4 Merg•cm-2) of UV-radiation on the ripening of tomato pericarp discs by measuring different characteristics of ripening and senescence during storage. We observed that UV-treatment induced significant delays of the red color development, chlorophyll degradation, and lycopene production compared to control discs. UV-treatment also retarded the decline of the chlorophyll-a fluorescence ratios Fv: Fm and *F : Fm′, two characteristics related, respectively, to the maximum and operational quantum yield of photosystem II electron transport. Furthermore, the climacteric ethylene peak was delayed in the treated discs. However, UV-treatment did not alter textural changes, and the respiratory climacteric peaks were observed concomitantly for both treated and untreated tomato discs. However, the respiratory rate was consistently higher in treated discs. These results indicate that UV irradiation of tomato pericarp discs delays some processes of ripening associated with chloroplast to chromoplast transition whereas other ripening processes seem unaffected.

Free access

Francesco Montesano and Marc W. van Iersel

The availability of good quality irrigation water is decreasing worldwide, and salinity is an increasingly important agricultural problem. To determine whether detrimental effects of NaCl can be minimized by additional Ca2+, tomato (Lycopersicon esculentum Mill.) `Super-sweet 100' was grown hydroponically. The basic nutrient solution contained 11.9 mM NO - 3 and 3.2 mM Ca 2+. We added 14.1, 44.4 and 70.4 mM of NaCl to this solution to determine the effect of NaCl and there were treatments with 70 mM NaCl and 10 or 20 mM Ca2+ to look at Ca2+ effects. We also included three treatments in which all nutrient concentrations were increased (without NaCl) to distinguish between osmotic and ion-specific effects. 70.4 mM NaCl reduced leaf photosynthesis, chlorophyll content, gas phase conductance for CO2 diffusion, carboxylation efficiency, and dark-adapted quantum yield of photosystem II. The inclusion of 20 mM Ca2+ prevented these effects of NaCl. NaCl also decreased leaf size and elongation rate, but this could not be prevented by adding extra Ca2+ to the nutrient solution; these were caused by osmotic effects, rather than Na+ specifically. Likewise, plant dry mass was negatively correlated with solution EC, suggesting an osmotic effect. Our results indicate that leaf area development, which was inhibited by high EC, is more important for dry matter accumulation than leaf photosynthesis, which was inhibited by high Na+. Adding 20 mM Ca2+ to the 70 mM NaCl solution reduced the Na+ concentration in the leaf from 79 to 24 mg·g-1, which may explain why Ca2+ alleviates Na+ toxicity.

Full access

He Li, Matthew Chappell and Donglin Zhang

its comparably dense habit ( Table 5 ). Table 5. Field performance rating, net growth, and percentage of decrease in maximum quantum yield of photosystem II (F v /F m ) of 10 mountain laurel cultivars at the University of Georgia Riverbend Research