Relationship between fluorescence yield and photochemical yield under water stress and intermediate light conditions

We tested the response of seedlings of Dicorynia guianensis, a major timber tree species of French Guiana, to mycorrhizal symbiosis and water limitation in a semi-controlled experiment under natural light conditions. Under well-watered conditions, mycorrhizal colonization resulted in an increase of net photosynthesis, growth and phosphorus uptake. When submitted to water stress, no growth reduction of mycorrhizal seedlings was observed. Mycorrhizal seedlings were more sensitive to drought than non-mycorrhizal ones in terms of carbon assimilation, but not with regard to stomatal closure. In contrast to previous studies on temperate tree seedlings, this result precludes a mycorrhizal effect on the hydraulic properties of this species. Furthermore, our results suggest that below a specific threshold of soil moisture, carbon assimilation of D. guianensis seedlings was decreased by the mycorrhizal symbiosis. This is probably related to the competition between the plant and its host fungus for carbon allocation under low light intensity, even though it did not seem to have a significant effect on mortality in our experiment.

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The wavelength- and temperature-dependence of the fluorescence efficiency and of the primary photochemical yield in hexafluoroacetone vapour

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1959.0064 ◽

1959 ◽

Vol 250 (1262) ◽

pp. 287-300 ◽

Cited By ~ 10

Keyword(s):

Excitation Energy ◽

Temperature Dependence ◽

Room Temperature ◽

Wavelength Dependence ◽

Fluorescence Yield ◽

A Value ◽

Fluorescence Efficiency ◽

Vibrational Levels ◽

Photochemical Yield ◽

The One

The measurement of the fluorescence and photochemical yields of hexafluoroacetone previously made at 3130 Å and at room temperature is extended to various other wavelengths and temperatures. Relative fluorescence yields at room temperature increase with decrease of excitation energy. This wavelength dependence is smaller at higher concentrations. The yields increase with concentration eventually converging almost to a single value. On the other hand, the photochemical yields measured show the opposite trends with respect to variations in concentration and excitation energy. As concentration increases they also converge to a value almost identical with that at 3130 Å. The temperature effect on the fluorescence yield is also opposite to the one on the photolysis at 3130 Å. The fluorescence decreases with increase in temperature, the variation being much bigger at higher concentrations. The intensity distribution of the fluorescence band is independent of temperature. It seems difficult to interpret the observed temperature dependence for fluorescence quenching and for dissociation at infinite concentration on the basis of a single excited state. Two modes of dissociation are postulated arising respectively from low and from high vibrational levels of different electronic states.

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Diurnal Response of Sun-Induced Fluorescence and PRI to Water Stress in Maize Using a Near-Surface Remote Sensing Platform

Remote Sensing ◽

10.3390/rs10101510 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1510 ◽

Cited By ~ 12

Author(s):

Shan Xu ◽

Zhigang Liu ◽

Liang Zhao ◽

Huarong Zhao ◽

Sanxue Ren

Keyword(s):

Water Stress ◽

Near Infrared ◽

Stomatal Closure ◽

Canopy Structure ◽

Early Morning ◽

Fluorescence Yield ◽

Operating Efficiency ◽

Photochemical Quenching ◽

Near Surface ◽

The Impact

Sun-induced Fluorescence (SIF) and Photochemical Reflectance Index (PRI) data were collected in the field over maize to study their diurnal responses to different water stresses at the canopy scale. An automated field spectroscopy system was used to obtain continuous and long-term measurements of maize canopy in four field plots with different irrigation treatments. This system collects visible to near-infrared spectra with a spectrometer, which provides a sub-nanometer spectral resolution in the spectral range of 480~850 nm. The red SIF (FR) and far red SIF (FFR) data were retrieved by Spectral Fitting Methods (SFM) in the O 2 -A band and O 2 -B band, respectively. In addition to PRI, Δ PRI values were derived from PRI by subtracting an early morning PRI value. Photosynthetic active radiation (PAR) data, the canopy fraction of absorbed PAR (fPAR), and the air/canopy temperature and photosystem II operating efficiency (YII) at the leaf scale were collected concurrently. In this paper, the diurnal dynamics of each parameter before and after watering at the jointing stage were compared. The results showed that (i) both FR and FFR decreased under water stress, but FR always peaked at noon, and the peak of FFR advanced with the increase in stress. Leaf folding and the increase in Non-photochemical Quenching (NPQ) are the main reasons for this trend. Leaf YII gradually decreased from 8:00 to 14:00 and then recovered. In drought, leaf YII was smaller and decreased more rapidly. Therefore, the fluorescence yield at both the leaf and canopy scale responded to water stress. (ii) As good indicators of changes in NPQ, diurnal PRI and Δ PRI data also showed specific decreases due to water stress. Δ PRI can eliminate the impact of canopy structure. Under water stress, Δ PRI decreased rapidly from 8:00 to 13:00, and the maximum range of this decrease was approximately 0.05. After 13:00, their values started to increase but could not recover to their morning level. (iii) Higher canopy-air temperature differences ( Δ T ) indicate that stomatal closure leads to an increase in leaf temperature, which maintains a higher state in the afternoon. In summary, to cope with water stress, both leaf folding and changes in physiology are activated. To monitor drought, SIF performs best around midday, and PRI is better after noon.

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Factors Affecting Germination of Citronmelon (Citrullus lanatusvar.citroides)

Weed Science ◽

10.1614/ws-d-13-00041.1 ◽

2014 ◽

Vol 62 (1) ◽

pp. 45-50 ◽

Cited By ~ 11

Author(s):

Analiza Henedina M. Ramirez ◽

Amit J. Jhala ◽

Megh Singh

Keyword(s):

Water Stress ◽

Environmental Factors ◽

Climatic Conditions ◽

Dark Condition ◽

Light Conditions ◽

Factors Affecting ◽

Wide Range ◽

Citrus Orchards ◽

Favorable Weather ◽

Effect Of Light

Citron melon is a monoecious, hairy annual vine commonly found in citrus orchards, and cotton and peanut fields. Information is not available on the effect of various environmental factors on the germination of citron melon. Laboratory and greenhouse experiments were carried out in 2011 and 2012 to determine the effect of light, temperature, salinity, pH, simulated water stress, and depth of sowing on the germination of citron melon. Citron melon germination was affected by various environmental factors. Highest germination was observed at day/night temperatures of 25/20 to 30/25 C regardless of light conditions. At temperatures below 25 C and beyond 35 C, germination declined and was higher under dark condition than light. Germination decreased as osmotic potential became more negative (−0.3 MPa to −1.5 MPa) and salt concentration increased (50 to 350 mM). No germination was observed at > −0.9 MPa and ≥ 300 mM salt concentrations. However, germination was observed over a broad range of pH (3 to 9) and up to 10-cm sowing depths. Seeds sown at the surface did not germinate but maximum germination (88 to 96%) occurred at 2- to 4-cm depth. The results of this study suggest that citron melon can grow in a wide range of climatic conditions and therefore can persist in Florida because of favorable weather and environmental conditions.

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THE PHOTOLYSIS AND THE FLUORESCENCE OF PERFLUORO DIETHYL KETONE

Canadian Journal of Chemistry ◽

10.1139/v60-010 ◽

1960 ◽

Vol 38 (1) ◽

pp. 104-111 ◽

Cited By ~ 4

Author(s):

G. Giacometti ◽

H. Okabe ◽

S. J. Price ◽

E. W. R. Steacie

Keyword(s):

Photochemical Reaction ◽

Strong Dependence ◽

Wavelength Region ◽

Fluorescence Yield ◽

Fluorescence Band ◽

Reaction Products ◽

Concentration Region ◽

Diethyl Ketone ◽

Photochemical Yield ◽

Primary Photochemical Reaction

The photolysis and the fluorescence of C2F5COC2F5 have been studied at various temperatures, concentrations, and wavelengths. There is a strong dependence of the photochemical yield and to a lesser extent of the relative fluorescence yield on these factors. The reaction products are solely CO and C4F10. The fluorescence is excited by light of the wavelength region between 2537 Å and 3650 Å. The fluorescence band lies in almost the same wavelength region as that of CF3COCF3 and the relative fluorescence yield is slightly less in the higher concentration region. This behavior closely follows the pattern for CF3COCF3 and, hence, may be discussed by the same mechanism. A comparison is made of the primary photochemical reaction among fluorinated ketones.

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GROWTH PERFORMANCE AND STABILITY ANALYSIS OF SOME WHEAT GENOTYPES SUBJECTED TO WATER STRESS AT RAWALAKOT AZAD JAMMU AND KASHMIR

Archives of Agronomy and Soil Science ◽

10.1080/0365034031000155040 ◽

2003 ◽

Vol 49 (4) ◽

pp. 415-426

Author(s):

M KALEEM ABBASI ◽

RASHID HUSSAIN KAZMI ◽

M QAYYUM KHAN

Keyword(s):

Stability Analysis ◽

Water Stress ◽

Growth Performance ◽

Jammu And Kashmir ◽

Wheat Genotypes

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Changes in essential oil content and composition of Agastache foeniculum under water stress at second harvest

Planta Medica ◽

10.1055/s-0031-1282322 ◽

2011 ◽

Vol 77 (12) ◽

Author(s):

M Mahmoodi Sourestani ◽

F Malekshahi

Keyword(s):

Water Stress ◽

Essential Oil ◽

Oil Content

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Biscogniauxia (Hypoxylon) Canker or Dieback in Trees

EDIS ◽

10.32473/edis-fr407-2017 ◽

2017 ◽

Vol 2017 (6) ◽

Author(s):

Claudia Paez ◽

Jason A. Smith

Keyword(s):

Water Stress ◽

Tree Species ◽

Soil Compaction ◽

Urban Areas ◽

Root Disease ◽

Poor Health ◽

Green Spaces ◽

Opportunistic Pathogens ◽

Wide Range ◽

Quercus Spp

Biscogniauxia canker or dieback (formerly called Hypoxylon canker or dieback) is a common contributor to poor health and decay in a wide range of tree species (Balbalian & Henn 2014). This disease is caused by several species of fungi in the genus Biscogniauxia (formerly Hypoxylon). B. atropunctata or B. mediterranea are usually the species found on Quercus spp. and other hosts in Florida, affecting trees growing in many different habitats, such as forests, parks, green spaces and urban areas (McBride & Appel, 2009). Typically, species of Biscogniauxia are opportunistic pathogens that do not affect healthy and vigorous trees; some species are more virulent than others. However, once they infect trees under stress (water stress, root disease, soil compaction, construction damage etc.) they can quickly colonize the host. Once a tree is infected and fruiting structures of the fungus are evident, the tree is not likely to survive especially if the infection is in the tree's trunk (Anderson et al., 1995).

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Citrus Irrigation Management

EDIS ◽

10.32473/edis-ss660-2017 ◽

2017 ◽

Vol 2017 (5) ◽

Author(s):

Davie Mayeso Kadyampakeni ◽

Kelly T. Morgan ◽

Mongi Zekri ◽

Rhuanito Ferrarezi ◽

Arnold Schumann ◽

...

Keyword(s):

Water Stress ◽

Physiological Activity ◽

Irrigation Management ◽

Fruit Size ◽

Irrigation Scheduling ◽

Leaf Expansion ◽

Tree Canopy ◽

Limiting Factor ◽

Irrigation Frequency ◽

Citrus Production

Water is a limiting factor in Florida citrus production during the majority of the year because of the low water holding capacity of sandy soils resulting from low clay and the non-uniform distribution of the rainfall. In Florida, the major portion of rainfall comes in June through September. However, rainfall is scarce during the dry period from February through May, which coincides with the critical stages of bloom, leaf expansion, fruit set, and fruit enlargement. Irrigation is practiced to provide water when rainfall is not sufficient or timely to meet water needs. Proper irrigation scheduling is the application of water to crops only when needed and only in the amounts needed; that is, determining when to irrigate and how much water to apply. With proper irrigation scheduling, yield will not be limited by water stress. With citrus greening (HLB), irrigation scheduling is becoming more important and critical and growers cannot afford water stress or water excess. Any degree of water stress or imbalance can produce a deleterious change in physiological activity of growth and production of citrus trees. The number of fruit, fruit size, and tree canopy are reduced and premature fruit drop is increased with water stress. Extension growth in shoots and roots and leaf expansion are all negatively impacted by water stress. Other benefits of proper irrigation scheduling include reduced loss of nutrients from leaching as a result of excess water applications and reduced pollution of groundwater or surface waters from the leaching of nutrients. Recent studies have shown that for HLB-affected trees, irrigation frequency should increase and irrigation amounts should decrease to minimize water stress from drought stress or water excess, while ensuring optimal water availability in the rootzone at all times.

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