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
Wenjie Ma, Wen Liang, and Bing Zhao
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
Stephanie Brown and Alejandro Ching
A photosynthesis study was conducted on seedlings of Lycopersicon esculentum L. cv. “Traveller 76” subjected to natural, clear, blue and red color irradiations to predict and evaluate harvest time and yield potential. Photosynthesis (PS) rates were higher on clear and red irradiated transplants with 16.1 and 12.4 μMol/m2/s, respectively, for two weeks of treatment. Blue irradiation showed lowest PS rate with 2.2 μMol/m2/s. For the third and fourth weeks of treatment, PS rate increased to 10.9 and 13.5 μMol/m2/s, respectively, on blue light treated transplants, while red, clear and natural light treatments decreased. CO2 appears to be lowest at high PS rate under these treatments. Transplants treated with blue and red lights were taller and thicker around the stem. Clear and natural lights were shorter, but with a larger root biomass. PAR (Photosynthetically Active Radiation) was highest at noon under open natural light with 1108.8 μE/s/m2, but also high for blue, red and clear lights when compared to earlier or later time. The lowest PAR was shown for blue and red lights.
Manuela Zude-Sasse, Ulrich Hartmond, Georg Ebert, and Peter Lüdders
Soil flooding reduces partial pressure of oxygen (pO2) in the root zone and often results in a reduction in photosynthesis and growth. In greenhouse studies, rooted stem cuttings of the mango (Mangifera indica L.) rootstock selection 13/1 were exposed to anoxia by saturating the root zone with N2 for up to 52 h. Reduced pO2 in the root zone affected the energy status of the roots and particularly enhanced the phosphorylated and nonphosphorylated pyridine nucleotide charges—the ratio of reduced Nicotinamide-adenine-dinucleotides [NAD(P)H] to total Nicotinamide-adenine-dinucleotide content [oxidized NAD(P)+ plus NAD(P)H]—that drive the redox reaction rates in cell metabolism. Also, the pyridine nucleotide charges in leaves were enhanced, while the photosynthetic rate decreased following reduction in pO2 in the root zone. During up to 4 h of reduced pO2, the ratio of internal CO2 concentration in the mesophyll to ambient CO2 concentration was unchanged. This implies a nonstomatal influence on photosynthesis. In addition, light saturation of photosystem II occurred at lower irradiance (470 μmol·m-2·s-1) resulting in reduced maximum photochemical efficiency below that of the high pO2 controls. After 28 h of reduced pO2, NAD(P) charges in the leaves returned to normal, diminishing its potential effect on net photosynthetic rate.
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
Tonghua Pan, Juanjuan Ding, Gege Qin, Yunlong Wang, Linjie Xi, Junwei Yang, Jianming Li, Jing Zhang, and Zhirong Zou
400 μmol·mol –1 , and this value is projected to double by the end of 21st century ( Urban et al., 2014 ). However, in a closed greenhouse, as plants absorb CO 2 for photosynthesis, CO 2 levels may fall to as low as 150 μmol·mol –1 in bright
David J. Ballantyne
The influence of photosynthetic photon flux density (PPFD) and gibberellic acid (GA3) sprays on shoot elongation was determined for `Coral Bells' (Kurume or R. obstusum hybrid), `Fashion' (Glen Dale or R. indicum × Kurume hybrid), `Hexe' (R. obtusum × R. simsii hybrid), `Hinocrimson' (Kurume or R. obtusum hybrid), `Hinodegiri' (Kurume or R. obtusum hybrid), and `Red Wing' (Brooks hybrid) azalea. GA3 at 1 mm was more effective in stimulating shoot elongation of `Coral Bells', `Fashion', `Hinodegiri', and `Red Wing' than of `Hexe' or `Hinocrimson'. GA3 sprays were more effective in stimulating elongation when applied to plants growing at irradiance levels of 350 μmol·s-1·m-2 than to plants growing at either 200 or 100 μmol·s-1·-2. Gross photosynthesis of leaf segments was higher for a slow-growing cultivar (Hinocrimson) than for a faster-growing cultivar (Fashion). `Hinocrimson' produced stouter shoots (greater dry weight/cm) than did `Fashion'.
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
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
Matthew Arrington, Mateus S. Pasa, and Todd C. Einhorn
rates of all ABA treatments were ≥90% of controls. Fig. 2. The effect of abscisic acid rate on photosynthesis ( P n ) of ‘Bartlett’ pear leaves in Expt. 3 ( A ) and Expt. 2 ( B ). Measurements were taken at solar noon (±1 h). Data are means of four