Field experiment to assess the impact of radiation, temperature and foliar N application on rice was conducted. The treatments comprised of four sunlight levels, [control, 50% intensity during start to maximum tillering (R15–45), maximum tillering to booting (R46–75) and panicle emergence to maturity (R76–105) corresponding to 15–45, 46–75 and 76–105 days after transplanting] and 5 levels of foliar nitrogen [control, spray of 3% urea solution in water before (NB), midway (NM), afterwards (NA) and midway + afterwards (NMA) reduction in sunlight]. Results showed that leaf chlorophyll had an inverse relationship with radiation intensity. The R46–75 significantly reduced effective tillers (13.1–16.4%), R46–75 and R76–105 reduced grains/panicle (7.15–12.5%) as compared to control. NB produced significantly higher effective tillers (21.9–24.7%) and grains/panicle (12.2–12.9%) as compared to control. The reduction in sunlight and application of foliar nitrogen increased the minimum cooking time and decreased elongation ratio. Averaged over locations, R15–45, R46–75 and R76–105 decreased the yield significantly as compared to control by 9.29–11.3, 14.4–16.3 and 8.17–10.6%, respectively. The NB significantly increased grain yield as compared to control by 10.3% (Ludhiana) and 9.45% (Hoshiarpur). A decrease in maximum temperature (Tmax) by 2.85–5.70% (1–2°C) of 35.1°C, at 1416 μmol/m2/s of photosynthetically active radiation (PAR) increased rice productivity by 10.6–21.0%, while a similar decrease in PAR by 2.85–5.70% at a Tmax of 35.1°C, decreased the productivity by 2.05–4.10%. So, decrease in Tmax due to cloudy weather might have a positive influence while negative impact of deficit radiation may be mitigated by foliar application of 3% urea prior to/during the cloudy weather.

Drought is considered as the major environmental stress affecting coffee production, and high phosphorus (P) supply may alleviate the drought effects on crop metabolism. Here, we hypothesized that high P supply would mitigate the impacts of drought on Arabica coffee physiology, morphology, and biomass accumulation. Potted Arabica coffee plants were grown under two P levels: the recommended P fertilization (P), and twice the recommended fertilization (+P), and two water regimes: well-watered and water withholding for 32 days. Leaf, stem, and root P concentrations were increased under +P, with plants showing higher photosynthesis and growth than the ones receiving the recommended P dose. Higher plant growth under high P supply seems to upregulate leaf photosynthesis through the source–sink relationship. Under the water deficit, the reduction of leaf photosynthesis, stomatal conductance, transpiration, water use efficiency, carboxylation efficiency, chlorophyll content, number of plagiotropic branches, plant leaf area, and vegetative biomass production was similar comparing plants fertilized with the recommended P to those supplied with +P. However, Arabica coffee trees under high P supply and water deficit presented morphological and physiological traits similar to plants under well-watered and recommended P fertilization.

Alga in the genus Chroothece have been reported mostly from aquatic or subaerial continental environments, where they grow in extreme conditions. The strain Chroothece mobilis MAESE 20.29 was exposed to different light intensities, red and green monochromatic light, ultraviolet (UV) radiation, high nitrogen concentrations, and high salinity to assess the effect of those environmental parameters on its growth. Confocal laser scanning microscopy (CLSM) was used as an “in vivo” noninvasive single-cell method for the study. The strain seemed to prefer fairly high light intensities and showed a significant increase in allophycocyanin (APC) and chlorophyll a [photosystem I (PSI) and photosystem II (PSII)] fluorescence with 330 and 789 μM/cm2/s intensities. Green monochromatic light promoted a significant increase in the fluorescence of APC and chlorophyll a (PSI and PSII). UV-A significantly decreased phycocyanin and increased APC, while UV-A + B showed a greater decreasing effect on c-Phycocyanin but did not significantly change concentrations of APC. The increase in nitrogen concentration in the culture medium significantly and negatively affected all pigments, and no effect was observed with an increase in salinity. Our data show that CLSM represents a very powerful tool for ecological research of microalgae in small volumes and may contribute to the knowledge of phycobiliproteins in vivo behavior and the parameters for the large-scale production of these pigments.

Conservation agriculture (CA) and no-till (NT)-based cropping systems could address soil degradation and fertility decline in southern Africa. A multi-location and multi-year experiment was carried out between 2008 and 2014 to assess the effects of different levels of maize residue biomass (0, 2, 4, 6 and 8 t ha−1) and nitrogen (N) fertilizer (0, 30, 90 kg ha−1) on maize performance under no-tillage. In some sites, different (N) fertilizer levels were superimposed to test their effects on maize grain yield and leaf chlorophyll content under different maize residue biomass levels. The different residue levels had no significant effect on maize yield in most growing seasons. Maize residue cover increased grain yield in eight out of 39 site-years across the sites used. However, in some sites, maize yield decreased with increases in residue level in cropping seasons that had average to above average rainfall. At a few sites maize yield increased with increase in residue level. Seasonal rainfall pattern influenced the effect of different residue levels on grain yield at most sites. Nitrogen fertilizer increased maize yield regardless of the residue level applied. This study demonstrates that mulching with maize residues in CA/NT systems results in limited maize yield gains – at least within the first 6 years in different agro-ecological conditions of southern Africa.

Multispectral imaging is a new technology that is being deployed to assess seed quality parameters. Examples of applications in the detection and identification of fungi on seeds are presented, together with an example of the technology used for maturity determination in sugar beet seed. Results from multispectral imaging are compared with reference methods, and a high correlation is found. Applications of the technique for varietal discrimination and insect damage are also presented. There is a need for non-destructive, reliable and fast techniques, and it is concluded that multispectral imaging has potential for seed quality assessment, in particular for those components associated with surface structure and chemical composition, seed colour, morphology and size.

An Iranian sepiolite was activated with 1.5 M HCl. During activation, the specific surface area increased from 105 to 168 m2/g and the SiO2 content increased from 45.4 to 51.6%. The roles of temperature and time and the amount of acid-activated sepiolite used, were investigated and the optimum conditions, where chlorophyll, β-carotene, free fatty acid and peroxide were at their minimum levels, were determined for bleaching of canola oil by applying response surface methodology (RSM). Optimum bleaching conditions were obtained by adding 3% of acid-activated sepiolite at a temperature of 110°C with a bleaching time of 42.46 min during which, the amount of chlorophyll-α, β-carotene, free fatty acid and peroxide were reduced from 12.30 to 0.35 mg/kg, 49.15 to 14.98 mg/kg, 0.62 to 0.15%, and 3.87 to 2.14 meq O2/kg of oil, respectively. At optimum conditions, sepiolite displayed a greater capacity for removal of chlorophyll and β-carotene than a commercial bentonite bleaching agent.

The potential for yellow nutsedge (Cyperus esculentus L. var. leptostachyus Boeck. # CYPES) regrowth was reduced by increasing plant age and by glyphosate [N-(phosphonomethyl)glycine] and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene]. Of the amount of glyphosate transported to underground parts, most was found in the tubers, with immature rhizomes, roots, and tubers having 2 to 3 times higher concentrations than comparable mature tissues. Addition of unlabeled oxyfluorfen as a tank mixture with glyphosate increased absorption and translocation, mainly into leaves and new tubers, of radioactivity from 14C-glyphosate in 30-day-old plants. In contrast to the younger plants, the addition of oxyfluorfen decreased 14C-glyphosate detected in 60-day-old plants. The greater effectiveness of glyphosate when applied with oxyfluorfen on yellow nutsedge at the early growth stage has important implications in the field because the tuberization process must be stopped early in the development of the plant for successful control.

Oxyfluorfen [2 - chloro -1 - (3 - ethoxy - 4 - nitrophenoxy) -4 - (trifluoromethyl)benzene] and RH-8817 {ethyl 5 - [2-chloro - 4 -{trifluoromethyl) phenoxy] - 2 - nitrobenzoate} require light for activation. Removal of carotenoids by treating corn (Zea mays L.) seedlings with norflurazon [4 - chloro - 5 - (methylamino) - 2 - (α, α, α - trifluoro -m - tolyl) - 3 (2H) - pyridazinone] rendered them partially tolerant of oxyfluorfen and RH-8817 even when grown in the light. The activation of substituted diphenylether herbicides may occur as a result of the absorption of light energy by carotenoids.

Herbicidal activity of foliar-applied oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] was light dependent in buckwheat (Fagopyrum esculentum Moench. ‘Tokyo’). Plants were not injured when placed in the dark for as long as 4 days after herbicide treatment. When these plants were brought to the light, injury occurred, albeit more slowly than when plants were placed in the light immediately after treatment. The rate of injury increased as light intensity increased. The most effective wave length was 565 to 615 ηm, suggesting the involvement of a pigment with its absorption spectrum in this region. Chlorophyll content was not reduced by oxyfluorfen. Preliminary evidence suggests that photosynthesis was affected only after membrane integrity was disrupted.

Laboratory assays were conducted to determine the sensitivity of tomato and tobacco cell suspension cultures and tomato and pepper cotyledons to clomazone. A comparison of fresh weight and carotenoid content indicated up to a three-fold difference between the clomazone-tolerant tobacco and clomazone-susceptible tomato cell suspension cultures. In contrast, an approximate 60-fold difference between the tolerant pepper and susceptible tomato cotyledons was observed when total chlorophyll and carotenoid contents were measured. The effect of clomazone and its possible metabolites on in vivo and in vitro extractable IPP isomerase (EC 5.3.3.2) and prenyltransferase (EC 2.5.1.29) activity was investigated. There was no clear inhibitory effect of clomazone or possible clomazone metabolites upon enzyme activity in tomato or tobacco cell suspension cultures or on light or dark grown tomato or pepper cotyledons. No specific enzymatic target site of clomazone was identified in correlation with the reduction in total chlorophyll or carotenoid content.

Many natural and synthetic plant compounds become toxic when irradiated by ultraviolet or visible light. These compounds may be considered for use as herbicides, remembering the requirement for light. Concurrently, methods for blocking metabolic pathways so that phototoxic intermediates accumulate and thus kill the plant also have been studied. The mechanisms of action of potentially useful plant phototoxins are described.

Norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] decreased the total chlorophyll content and the chlorophyll a/b ratio of nine plant species. Grain sorghum [Sorghum bicolor (L.) Moench.], wheat (Triticum aestivum L.), and sicklepod (Cassia obtusifolia L. ♯3 CASOB) were the most susceptible plants, and cotton (Gossypium hirsutum L.) was the most tolerant. The soil properties most closely correlated with norflurazon activity were organic matter content and clay component, not clay content. A high treatment rate was necessary for effective control of plant growth in soil high in organic matter content and high in montmorillonite or vermiculite. Approximately twice as much norflurazon was required to reduce chlorophyll content 50% when applied to the soil preplant incorporated as was required when applied preemergence.

The effect of glyphosate [N-(phosphonomethyl) glycine] on barley (Hordeum vulgare L.) and corn (Zea mays L.) shoot δ-aminolevulinic acid (ALA) production was examined by monitoring ALA content in the tissue and measuring incorporation of 14C precursors into ALA and chlorophyll a. Barley shoot ALA content was significantly decreased by 1 mM glyphosate after 9, 11, and 15 h of illumination. ALA production by treated barley shoots was 30 nmoles•g fresh weight-1•h-1 at each interval tested, compared with 75 to 120 nmoles•g fresh weight-1•h-1 for the control. In corn shoots, ALA content was reduced 32, 45, and 58% by 0.1, 1.0, and 10.0 mM glyphosate, respectively, after 12 h illumination. Incorporation studies with 14C-glutamate, 14C-α-ketoglutarate, and 14C-glycine into ALA showed a 77, 92, and 91% inhibition, respectively, in barley shoots treated with 1 mM glyphosate. Incorporation of 14C-ALA into chlorophyll a was not affected by 1 mM glyphosate. Thus, the site of action of glyphosate may involve two enzyme pathways:one controlling the conversion of α-ketoglutarate to ALA, and the other controlling the condensation of glycine with succinyl CoA to form ALA and carbon dioxide. Inhibition of ALA synthesis blocks synthesis of chlorophyll, as well as all other porphyrin ring compounds found in higher plants. Thus, inhibition of ALA synthesis may be an integral component of the herbicidal mode of action of glyphosate.

A laboratory bioassay was conducted to determine the differential tolerance of cole crops to clomazone as measured by extractable total chlorophyll and carotenoids. Clomazone concentrations causing 50% inhibition (I50) in the biosynthesis of total chlorophyll in broccoli, cauliflower, and green and red cabbage cotyledons were 16, 11, 3, and 11 μM, respectively, while I50 values for carotenoid levels were 20, 10, 4, and 8 μM clomazone, respectively. Therefore, broccoli was the most tolerant to clomazone based upon extractable chlorophyll and carotenoid concentrations. Further laboratory studies were performed to investigate the basis for differential clomazone tolerance in 3-wk-old cole crop seedlings. No differences in total root uptake of 14C-clomazone were observed between these crops after 24 h. There were no differences in rate of metabolism of 14C-clomazone to methanol-soluble metabolites in roots of these crops. Percentage of polar metabolites in roots remained fairly constant over time. There were also no differences between crops in percentage of methanol-soluble 14C-clomazone metabolites formed in shoots between 24 and 96 h. In all crops, levels of 14C-clomazone decreased in a similar manner over time in methanolic extracts of roots and shoots while nonextractable 14C levels increased, indicating a conversion of clomazone to insoluble, nonextractable forms. Differential uptake, translocation, and metabolism do not appear to account for clomazone selectivity differences between cole crop seedlings.

The utility, advantages, and disadvantages of several spectrofluorometric and in vivo spectrophotometric methods in plant science are reviewed, with emphasis on their use in weed science. Examples of the use of in vivo, dual-wavelength spectrophotometry to probe the effects of herbicides on cytochrome f oxidation/reduction, the P515 chromatic shift, phytochrome synthesis, and other processes are discussed. Use of in vivo spectrophotometry to examine effects of herbicides on phytylation of chlorophyllide, protochlorophyllide photoconversion, porphyrin accumulation, and other processes that result in spectral changes is discussed and examples are provided. Spectrofluorometric methods for pigment identification and quantification and for enzyme assays are illustrated with examples. Spectrofluorometric methods used in conjunction with high-pressure liquid chromatography (HPLC) and thin-layer chromatography (TLC) are discussed.

Four days after treatment of corn (Zea mays L. 'SX111′) seedlings with BAS 9052 OH {2 - [1-(ethoxyimino) butyl] - 5 - [2 - (ethylthio) - propyl] - 3 - hydroxy - 2 - cyclohexene-1 - one} growth was inhibited and a purple color developed in the leaves. Low dosages (0.02 and 0.04 kg/ha) caused bleaching of the newly expanding leaves. Dosages higher than 0.04 kg/ha caused significant reductions in length and fresh and dry weights of both shoots and roots. Anthocyanin and total - sugar content increased, whereas chlorophyll accumulation and respiratory activity were reduced by herbicide treatment. BAS 9052 OH did not alter the mitotic index of corn root tips, but induced binucleate cells by preventing cell-plate and -wall formation. In some cells, the daughter nuclei were reoriented with respect to the longitudinal axis of the cells, and in others, the nuclei failed to migrate to the poles. These physiological and cytological effects of BAS 9052 OH on corn seedlings may be responsible for the phytotoxic action of the herbicide on grasses.

Investigations were conducted on Euglena gracilis Klebs strain Z to determine the effects of fluometuron [1,2-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea], MSMA (monosodium methanearsonate), glyphosate [N-(phosphonomethyl)glycine], and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] on cell number, chlorophyll content, and photosynthesis. Euglena cell number was reduced by 65% or more after 48 h with fluometuron levels above 4 X 10-5M. MSMA at 6 X 10-4M reduced cell number 42% after 144 h exposure. Chlorophyll content was reduced 33 to 80% by metribuzin levels of 2 X 10-6M or greater, and fluometuron inhibited chlorophyll content by 30% or more from 4 X 10-6M or greater concentrations. Chlorophyll was reduced 21 to 69% by treatment with glyphosate at 3 X 10-3M, but MSMA appeared to have little effect on chlorophyll except at the high level of 6 X 10-4M at 48 h. Photosynthesis was reduced 50% or more with metribuzin levels above 9 X 10-7M and with fluometuron above 9 X 10-5M. MSMA reduced photosynthesis by 20% at the 6 X 10-3M level, and glyphosate slightly reduced photosynthesis at levels below 1.2 X 10-4M but slightly stimulated it above that level. Chronic effects (Euglena exposed to herbicides 96 h prior to measurement) on photosynthesis indicated a more pronounced reduction from fluometuron than from short-term exposure, little change with glyphosate, but less reduction with metribuzin than from short-term exposure. Metribuzin caused increased respiration rates of 100 to 200% after 100 min of exposure. Respiration was stimulated 20% by glyphosate and relatively unaffected by the other compounds. Removal of Euglena from metribuzin- and fluometuron-treated media to non-treated media resulted in increased levels of chlorophyll to near that of the control. These results suggest that use of these herbicides is not detrimental to non-target algae if the exposure is not intensive.

The chlorophyll levels and growth of oat (Avena sativa L. ‘Elgin’) seedlings were drastically reduced after foliar application of diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate}. The leaves were chlorotic and necrotic with the newly emerging leaves being most affected. Plants treated with 2,4-D [(2,4-dichlorophenoxy)acetic acid] were similar to the controls. When 2,4-D was applied to intact plants in combination with diclofop-methyl the toxicity symptoms produced by diclofop-methyl were reduced. Diclofop-methyl disrupted membrane integrity and inhibited chlorophyll formation in excised leaf segments. Addition of 2,4-D with diclofop-methyl did not change the effects produced by diclofop-methyl alone in excised leaf segments.

Research was conducted to determine effects of glyphosate [N-(phosphonomethyl)glycine] on the chlorophyll and carotenoid and on the catalase specific activity in purple nutsedge (Cyperus rotundus L.). The isopropylamine salt of glyphosate caused chlorosis to appear on the center leaves of plants maintained under lighted conditions after treatment. Glyphosate-induced chlorosis was delayed by darkness but occurred when treated plants were placed in the light. Glyphosate caused significant reducations in the chlorophyll and carotenoids content of purple nutsedge leaves. Based on levels in untreated plants, carotenoid content was reduced more rapidly than chlorophyll in glyphosate-treated plants. The catalase specific activity was reduced by glyphosate to about 70% of the level in untreated plants. Interrelationships among the effects of glyphosate on the carotenoid and chlorophyll content and catalase activity were not determined but possible interactions are discussed.