Lower Chlorophyll Content Research Articles

Peel Color and Blemishes in ‘Granny Smith’ Apples in Relation to Canopy Light Environment

The dark green apple cultivar, Granny Smith (GS), makes up 25% of the South African apple industry. However, production of GS is becoming unprofitable as a result of a high incidence of sunburn, red blush, and pale green fruit that decreases the proportion of Class 1 fruit that is suitable for export to more lucrative markets. This study was conducted to investigate the relationship between canopy position and external fruit quality with the ultimate aim to devise pruning and training strategies to maximize export yield. During early fruit development [26 days after full bloom (DAFB)], chlorophyll concentrations were the highest in fruit from higher light environments. Good green color at harvest relied on exposure of fruit to high irradiance at this stage because 50% shading between 14 and 56 DAFB significantly decreased dark green color at harvest. Exposed fruit from the northern side of east–west rows received the highest irradiance throughout the season [53% of full sun photosynthetic photon flux (PPF)] and had the highest fruit surface temperature (on average 5 °C above ambient). A high proportion of exposed fruit from either side of the row developed red blush. Only 22% to 39% of exposed fruit from the outer canopy did not develop sunburn or red blush. Partially shaded fruit from the southern side of east–west rows received ≈5% of full sunlight and had the highest chlorophyll concentrations and darkest green color at harvest. Deeply shaded inner canopy fruit received ≈2% of full sunlight, had low chlorophyll concentrations, and were lighter green in color. The 10% darkest green fruit received moderately high irradiance (25% to 45% of full sun PPF) during early fruit development (until ≈80 DAFB) but became progressively shaded (3% of full sun PPF) during the latter half of the season. Fruit that developed sunburn and the lightest green fruit were exposed to high (1300 μmol·m−2·s−1) and extremely low (50 μmol·m−2·s−1) light, respectively, throughout their development. In conclusion, maximum chlorophyll synthesis and dark green color require an open canopy during the first half of fruit development, whereas shading is necessary during the latter half of fruit development to avoid the occurrence of sunburn, red blush, and photothermal destruction of chlorophyll. GS may benefit significantly from the installation of shade netting if combined with rigorous pruning and vigor control.

The role of emergent macrophytes in nutrient cycling in Lake Niepruszewskie (western Poland)

The role of emergent macrophytes in nutrient cycling in Lake Niepruszewskie (western Poland) The role of emergent macrophytes in nutrient cycling was investigated in the littoral zone of Lake Niepruszewskie, which is dominated by this type of vegetation. The lake is characterized by an advanced stage of eutrophication as is evident in the frequent blooms that cause low transparency and high concentrations of chlorophyll a and seston. The shoot biomass of Phragmites australis and Typha angustifolia is the major component of the plant cover with respect to nutrient accumulation. Other plants play a marginal role in the nutrient turnover of the studied lake.

Cadmium-induced oxidative stress and the response of the antioxidative defense system inSpartina densiflora

Spartina densiflora is an invasive cordgrass that is colonizing new habitats and ousting indigenous species in pro-oxidative environments like cadmium-polluted salt marshes in the Odiel estuary (Spain). The aim of our study was to characterize its antioxidative system in order to find out if the system underlies the tolerance of S. densiflora to cadmium toxicity. S. densiflora plants were firstly evaluated to ascertain its antioxidative status in the natural habitat and then they were cultured in the laboratory in unpolluted sand for 28 days. Throughout this period, plants acclimatized and oxidative stress markers reached stable low levels. Then, S. densiflora plants were exposed to cadmium concentrations (10, 100 and 1000 microM Cd) for another 28 days. Higher Cd content in leaves was related to higher level of reactive oxygen species (ROS) causing important oxidative cell damage (lipid peroxidation and lower chlorophyll content). However, S. densiflora possesses a well-organized and appropriately modulated antioxidative defense system which comprises enzymatic activities of guaiacol peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11) and superoxide dismutase (EC 1.15.1.1) coupled with the activation of the ascorbate cycle, including enzymatic activities of glutathione reductase (EC 1.6.4.2), dehydroascorbate reductase (EC 1.8.5.1) and monodehydroascorbate reductase (EC 1.6.5.4). This activation was sufficient to reduce Cd-induced ROS accumulation and oxidative damage caused by the lowest Cd-concentrations, but not by the highest Cd-concentration (1000 microM). Nevertheless, the antioxidant system seems to be efficient to achieve a tolerance to cadmium toxicity, allowing normal plant development, even at the presence of highest Cd concentration.

Spectral Signatures of Leaf Fall Diseases in Hevea Brasiliensis Using a Handheld Spectroradiometer

Subtle sensitive changes in leaf canopy reflectance of a disease infected trees can be detected by a spectroradiometer. A typical method of detecting tree stress caused by diseases or pest infestations includes the analysis of spectroradiometry. Early detection of forest tree stress would be useful to minimize tree losses especially in a forest plantation area. The main purpose of this study is to develop the spectral library of individual rubber trees being attacked by diseases using a ground-based handheld field spectroradiometer. The specific objective is to identify the spectral signature characteristics of healthy (control) and “unhealthy” or stressed rubber trees due to leaf diseases as causal factors. The spectral reflectance of each infected rubber tree was separated according to the different wavelength and percent reflectance. The spectral signatures of rubber trees being attacked by diseases were characterized by a low reflectance probably due to the low chlorophyll content in the leaves leading to the tree under stress, thus easily separated from the healthy rubber. Results indicated that three groups of infected trees were well separated at the 530 - 650 nm (visible) wavelength averaging from 0 – 30 percent reflectance. The spectral reflectances of rubber trees with leaf disease in visible (VIS) wavelength were not consistently separable. However, the spectral reflectance of leaf diseases can be well separated at the near infrared range region covering from 700 - 850 nm wavelength with a 30 – 80 percent reflectance for leaf diseases, respectively. The study implies that leaf diseases for rubber trees can only be identified successfully at the NIR range of wavelength from 700 – 850 nm with a 20-80 percent reflectance. The development of such signature library profile of disease affecting rubber trees will certainly assists in the development of an early disease warning system using an airborne hyperspectral imaging system technology being currently developed in UPM’s Forest Geospatial Information & Survey Laboratory, at Lebuh Silikon, Universiti Putra Malaysia, Serdang.

Characterization and mapping of a novel mutant sms1 (senescence and male sterility 1) in rice

Plant senescence plays diverse important roles in development and environmental responses. However, the molecular basis of plant senescence is remained largely unknown. A rice spontaneous mutant with the character of early senescence and male sterility (sms) was found in the breeding line NT10-748. In order to identify the gene SMS1 and the underlying mechanism, we preliminarily analyzed physiological and biochemical phenotypes of the mutant. The mutant contained lower chlorophyll content compared with the wild type control and was severe male sterile with lower pollen viability. Genetic analysis showed that the mutant was controlled by a single recessive gene. By the map-based cloning approach, we fine-mapped SMS1 to a 67 kb region between the markers Z3-4 and Z1-1 on chromo-some 8 using 1,074 F(2) recessive plants derived from the cross between the mutant sms1 (japonica) x Zhenshan 97 (indica), where no known gene involved in senescence or male sterility has been identified. Therefore the SMS1 gene will be a novel gene that regulates the two developmental processes. The further cloning and functional analysis of the SMS1 gene is under way.

EFFECT OF COLD STORAGE AND DIFFERENT PACKAGING MATERIALS ON THE QUALITY OF FRESH ROSEMARY HERB: I- EFFECTS ON MARKETING VISUAL QUALITY AND SHELF-LIFE

Fresh culinary herbs are one of the fastest growing markets for gourmet production on a world wide scale. Some herbs are sold fresh rather than dry because they do not retain their flavor when dried. Rosemary (Rosmarinus officinalis, L.) plant is an important aromatic culinary herb. A study was carried out during two successive summer seasons 2006 and 2007, at the Post Harvest Lab in the Veget. and Flor. Dept., Fac. of Agric., Monsoura Univ. Fresh rosemary herbs were packaged in nine different packaging materials: Butter bags (P1), Cellophane bags (P2), Nylon bags (P3), Polyethylene bags (P4), Aluminum foils (P5), Aluminum plates covered with foil (P6), Aluminum plates covered with plastic film (P7), Foam plates covered with foil (P8), Foam plates covered with plastic film (P9). The packages were stored at (room atmosphere, 1, 3, and 5 °C) for 6 weeks. This study was conducted to study the effect of cold storage and different packaging materials on the quality of rosemary fresh herb. This part (I): aimed to investigate the effect of cold storage temperatures and different packaging materials on the marketing visual quality and shelf life of fresh rosemary herb. The results showed that increasing storage period resulted in increasing of the fresh weight loss and decreasing the total chlorophyll content. While, the shortest storage period of the herb, the less the changes in their fresh weight, and the slowest the chlorophyll degradation. Herbs kept in Butter bags (P1) lost their fresh weight faster and sharper than those kept in other packaging materials, while those in Aluminum foils (P5) were the least to lose weight and had steadier pattern than the other packaging materials. Herbs kept in Butter bags (P1) and Foam plates covered with plastic film (P9) had lower chlorophyll content than other packages. At the end of the storage period (after six weeks), herbs kept in Aluminum foils (P5) and Aluminum plates covered with foil (P6) had the least fresh weight loss percentage, and the highest chlorophyll content in both seasons. It is also clear that Aluminum foils (P5) and Aluminum plates covered with foil (P6) kept the chlorophyll content of the herb at high values for long period especially at 1°C. The shelf life of the three storage temperatures varied slightly among each other’s but significantly with room temperature, with favor to the lower cold temperature. The worst package was Butter bags (P1) in both summer seasons. Aluminum foils (P5), Aluminum plates covered with foil (P6), and Foam plates covered with foil (P8) had longer shelf life than other packaging materials. Summing up all factors, herbs in Aluminum foils (P5) and Aluminum plates covered with foil (P6) storedat 3 °C maintained their fresh weight, chlorophyll content, and achieved longer shelf-life than other treatments in both seasons.

The dissolved yellow substance and the shades of blue in the Mediterranean Sea

Abstract. When the nominal algorithms commonly in use in Space Agencies are applied to satellite Ocean Color data, the retrieved chlorophyll concentrations in the Mediterranean Sea are recurrently notable overestimates of the field values. Accordingly, several regionally tuned algorithms have been proposed in the past to correct for this deviation. Actually, the blueness of the Mediterranean waters is not as deep as expected from the actual (low) chlorophyll content, and the modified algorithms account for this peculiarity. Among the possible causes for such a deviation, an excessive amount of yellow substance (or of chromophoric dissolved organic matter, CDOM) has been frequently cited. This conjecture is presently tested, by using a new technique simply based on the simultaneous consideration of marine reflectance determined at four spectral bands, namely at 412, 443, 490, and 555 nm, available on the NASA-SeaWiFS sensor (Sea–viewing Wide Field-of-view Sensor). It results from this test that the concentration in yellow colored material (quantified as ay, the absorption coefficient of this material at 443 nm) is about twice that one observed in the nearby Atlantic Ocean at the same latitude. There is a strong seasonal signal, with maximal ay values in late fall and winter, an abrupt decrease beginning in spring, and then a flat minimum during the summer months, which plausibly results from the intense photo-bleaching process favored by the high level of sunshine in these areas. Systematically, the ay values, reproducible from year to year, are higher in the western basin compared with those in the eastern basin (by about 50%). The relative importance of the river discharges into this semi-enclosed sea, as well as the winter deep vertical mixing occurring in the northern parts of the basins may explain the high yellow substance background. The regionally tuned [Chl] algorithms, actually reflect the presence of an excess of CDOM with respect to its standard (Chl-related) values. When corrected for the presence of the actual CDOM content, the [Chl] values as derived via the nominal algorithms are restored to more realistic values, i.e., approximately divided by about two; the strong autumnal increase is smoothed whereas the spring bloom remains as an isolated feature.

Phylogenetically-based variation in the regulation of the Calvin cycle enzymes, phosphoribulokinase and glyceraldehyde-3-phosphate dehydrogenase, in algae

Aquatic photosynthesis is responsible for about half of the global production and is undertaken by a huge phylogenetic diversity of algae that are poorly studied. The diversity of redox-regulation of phosphoribulokinase (PRK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was investigated in a wide range of algal groups under standard conditions. Redox-regulation of PRK was greatest in chlorophytes, low or absent in a red alga and most chromalveolates, and linked to the number of amino acids between two regulatory cysteine residues. GAPDH regulation was not strongly-related to the different forms of this enzyme and was less variable than for PRK. Addition of recombinant CP12, a protein that forms a complex with PRK and GAPDH, to crude extracts inhibited GAPDH and PRK inversely in the Plantae, but in most chromalveolates had little effect on GAPDH and inhibited or stimulated PRK depending on the species. Patterns of enzyme regulation were used to produce a phylogenetic tree in which cryptophytes and haptophytes, at the base of the chromalveolates, formed a distinct clade. A second clade comprised only chromalveolates. A third clade comprised a mixture of Plantae, an excavate and three chromalveolates: a marine diatom and two others (a xanthophyte and eustigmatophyte) that are distinguished by a low content of chlorophyll c and a lack of fucoxanthin. Regulation of both enzymes was greater in freshwater than in marine taxa, possibly because most freshwaters are more dynamic than oceans. This work highlights the importance of understanding enzyme regulation in diverse algae if their ecology and productivity is to be understood.

Interaction Between Calcium Concentration and Growth Irradiance on Photosynthesis and Growth of Temperate Lettuce in the Tropics

ABSTRACT Temperate lettuce (Lactuca sativa L.) was grown in the tropics under 100% (high light), 70% (medium light), and 40% (low light) of prevailing solar radiations. Their root zones were maintained at 25°C, while the shoots were exposed to hot ambient temperature. Three calcium (Ca) concentrations: −25% Ca (minus Ca), control (Ca) and +25% Ca (plus Ca) were supplied to the plants under each growth irradiance. Plants grown at the plus Ca under high light had the highest productivity, largest root system, highest photosynthetic capacity and highest Ca concentration. Grown at the minus Ca under low light they had the lowest values of these parameters. However, highest and lowest chlorophyll concentrations were found in plants grown at the plus Ca under low light and at the minus Ca under high light, respectively. When grown at the plus Ca under low light, plants transported higher portion of the absorbed Ca to the shoots.

Effects of Cultural System (Organic and Conventional) on Growth, Photosynthesis and Yield Components of Sweet Corn (Zea mays L.) under Semi-Arid Environment

Organic sweet maize consists of a new industrial crop product. Field experiment was conducted to determine the effects of cultural systems on growth, photosynthesis and yield components of sweet maize crop (Zea mays L. F1 hybrid Midas). A randomized complete block design was employed with four replicates per treatment (organic fertilization: cow manure (5, 10 and 20 t ha1), poultry manure (5, 10 and 20 t ha1) and barley mulch (5, 10 and 20 t ha1), synthetic fertilizer (240 kg N ha1): 21-0-0 and control). The lowest dry weight, height and leaf area index and soil organic matter were measured in the control treatment. Organic matter content was proportionate to the amount of manure applied. The control plots had the lowest yield (1593 kg ha-1) and the double rate cow manure plots the had greatest one. (6104 kg ha-1). High correlation between sweet corn yield and organic matter was registered. Moreover, the lowest values of 1000-grain weight were obtained with control plot. The fertilizer plot gave values, which were similar to the full rate cow manure treatment. The photosynthetic rate of the untreated control was significantly lower than that of the other treatments. The photosynthetic rate increased as poultry manure and barley mulch rates decreased and as cow manure increased. Furthermore, the untreated control had the lowest stomatal conductance and chlorophyll content. Our results indicated that sweet corn growth and yield in the organic plots was significantly higher than those in the conventional plots.

Differential Responses of Forage Pearl Millet Genotypes to Chinch Bug (Heteroptera: Blissidae) Feeding

Chinch bug, Blissus leucopterus leucopterus (Say) (Heteroptera: Blissidae), is one of the most important insect pests on forage pearl millet, Pennisetum glaucum L. R. Br., production in the southeastern United States. Twenty-nine forage pearl millet genotypes were assessed for chinch bug resistance by using stunt and necrosis ratings in combination with quantitative measurements of chlorophyll content and leaf photosynthetic rate. Plant stunt and leaf sheath necrosis ratings, and chlorophyll content in flag leaves differed among the 29 genotypes. Photosynthetic rate differed both among the noninfested control and among the chinch bug-infested plants. The chinch bug-infested plants had lower photosynthetic rate than the noninfested control plants. Inbreds with resistance superior to that of Tift 23DB were identified for hybrid development. When the 29 pearl millet genotypes were assessed by the six parameters by using cluster analysis, genotypes 07F-1226, 07F-1229, 07F-1231, 07F-1235, 07F-1238, 07F-1239, and 07F-1240 were the most resistant, whereas the genotypes 07F-1220, 07F-1221, 07F-1225, 07F-1227, 07F-1232, 07F-1246, and Tift 23DB were the most susceptible to chinch bug feeding. The rest of the genotypes expressed intermediate responses to the six parameters. To differentiate the physiological impact of chinch bug feeding on light and dark reactions of plant photosynthesis, photosynthesis capacity was assessed using light and CO2 (A/Ci) response curves on noninfested and chinch bug-infested plants of genotypes 07F-1246, 07F-1223, and 07F-1245, which expressed low, intermediate, and high chlorophyll content, respectively. Based on the A/Ci curves, photosynthesis capacity of injured leaves was suppressed in 07F-1223 and 07F-1246, whereas the chinch bug-injured 07F-1245 leaves showed an increase of photosynthetic rate compared with the noninfested plants. In contrast, light response curves were suppressed in the chinch bug-injured plants compared with the noninfested plants of all three genotypes, irrespective of their variations in insect injury ratings. This research demonstrated that visual stunt and necrosis rating methods in combination with chlorophyll and photosynthesis measurements could be used in screening forage pearl millet for chinch bug resistance and deciphering the underlying resistance mechanisms.

SAUR39, a small auxin-up RNA gene, acts as a negative regulator of auxin synthesis and transport in rice.

The phytohormone auxin plays a critical role for plant growth by regulating the expression of a set of genes. One large auxin-responsive gene family of this type is the small auxin-up RNA (SAUR) genes, although their function is largely unknown. The expression of the rice (Oryza sativa) SAUR39 gene showed rapid induction by transient change in different environmental factors, including auxin, nitrogen, salinity, cytokinin, and anoxia. Transgenic rice plants overexpressing the SAUR39 gene resulted in lower shoot and root growth, altered shoot morphology, smaller vascular tissue, and lower yield compared with wild-type plants. The SAUR39 gene was expressed at higher levels in older leaves, unlike auxin biosynthesis, which occurs largely in the meristematic region. The transgenic plants had a lower auxin level and a reduced polar auxin transport as well as the down-regulation of some putative auxin biosynthesis and transporter genes. Biochemical analysis also revealed that transgenic plants had lower chlorophyll content, higher levels of anthocyanin, abscisic acid, sugar, and starch, and faster leaf senescence compared with wild-type plants at the vegetative stage. Most of these phenomena have been shown to be negatively correlated with auxin level and transport. Transcript profiling revealed that metabolic perturbations in overexpresser plants were largely due to transcriptional changes of genes involved in photosynthesis, senescence, chlorophyll production, anthocyanin accumulation, sugar synthesis, and transport. The lower growth and yield of overexpresser plants was largely recovered by exogenous auxin application. Taken together, the results suggest that SAUR39 acts as a negative regulator for auxin synthesis and transport.

Chlorophyll, calcite, and suspended sediment concentrations in the Bay of Bengal and the Arabian Sea at the river mouths

Chlorophyll and suspended sediment concentrations (SSC) and sea surface temperature (SST) are important parameters in assessing the productivity of coastal regions. Numerous rivers flow into the eastern (Ganga, Subernarekha, Mahanadi, Godavari, Krishna, Penner, and Kaveri) and western (Narmada, Tapti, and Indus) coasts of the Indian sub-continent. Using IRS P4 (Oceansat-1) Ocean Color Monitor (OCM) and Moderate Resolution Imaging Spectroradiometer (MODIS) data, we have retrieved chlorophyll, calcite, and SSC near the mouth of these rivers for the period during 2000–2004. The maxima of chlorophyll-a concentrations at the river mouth is much higher for the Himalayan and north India rivers (Ganga, Subernarekha, Mahanadi, and Indus) (10–14 mg/m 3) compared to rivers in the southern parts of India (Kaveri and Penner) (∼4 mg/m 3). The maxima of calcite concentration (∼45 moles/m 3), chlorophyll (∼14 mg/m 3), and sediment concentrations (∼9 g/m 3) near river mouth are found to be influenced by river discharges (Ganga and Brahmaputra) during the monsoon season. The calcite concentration (∼45 moles/m 3) at the mouth of Ganga river shows a major peak with the onset of monsoon season (June–July) followed by a maxima in chlorophyll-a with a time lag of 1–2 months. The Krishna, Kaveri, and Penner rivers show low chlorophyll concentrations (3–8 mg/m 3), high calcite (0–40 moles/m 3), and low SSC (<3 g/m 3) compared to Narmada and Tapti rivers (chlorophyll-a 12–14 mg/m 3, calcite 0–2 moles/m 3, and SSC 13–19 g/m 3). The Indus river shows similar behavior (maxima of chlorophyll ∼13 mg/m 3 and SSC ∼8 g/m 3) with respect to Ganga river except for high calcite concentration during winter months (∼25 moles/m 3). The characteristics of the chlorophyll, calcite, and SSC at the mouth of these rivers show spatial and temporal variability along the eastern and westerns coasts of India which are found to differ widely. A comparison of the chlorophyll concentrations using OCM and MODIS data shows low chlorophyll concentrations in the Bay of Bengal as compared to the Arabian Sea.

Differences in leaf traits, leaf internal structure, and spectral reflectance between two communities of lianas and trees: Implications for remote sensing in tropical environments

Increasing dominance of lianas in many tropical forests is considered a fingerprint of global environmental change. Despite the key role they play in ecosystem functioning, lianas remain one of the least studied life forms in tropical environments. This paper contrasts leaf traits and spectral properties (400–1100 nm) of liana and tree communities from a tropical dry forest and a tropical rainforest in Panama, Central America. Differences between lianas and tree leaf traits were analyzed using spectroscopy, leaf histology and pigment extractions. Results from this study indicate that many of the biochemical, structural, and optical properties of lianas and trees are different in the dry forest site but not in rainforest sites. In the dry forest site, liana leaves exhibited significantly lower chlorophyll and carotenoid contents and were thinner than the leaves of their host trees. Specific leaf area, dry to fresh mass ratio, and mean water content of liana leaves were significantly higher when compared with tree leaves. The differences observed in the tropical dry forest site indicate that lianas may have a higher rate of resource acquisition and usage, whereas trees tend to conserve acquired resources. We suggest that our results may be indicative of the presence of a liana syndrome related to water availability and thus best exhibited in tropical dry forests. Our findings have important implications for using remote sensing to accurately map the distribution of liana communities at regional scales and for the continued expansion of lianas in tropical environments as a result of global change.

Rumen protozoa are rich in polyunsaturated fatty acids due to the ingestion of chloroplasts

Within this study, we investigated whether the polyunsaturated fatty acids (PUFA)-rich nature of rumen protozoa is a consequence of ingestion of PUFA-rich chloroplasts. Four Hereford x Friesian steers were offered hay [low 18:3 (n-3) and low chlorophyll concentration] followed by freshly cut perennial ryegrass [high 18:3 (n-3) and high chlorophyll concentration] for 16 days. On the 14th and 16th days, rumen protozoa as well as attached and planktonic bacteria were fractionated 1 h before (-1 h), 2 and 6 h postfeeding, and their fatty acid concentrations determined. Protozoa fractionated from fresh grass-fed steers were richer (P<0.05) in PUFA, except conjugated linoleic acid, for all time points compared with those from hay-fed steers. Protozoal density was higher (P<0.05) for grass compared with hay. Entodinomorphid abundance was 3.4 times higher on fresh grass (P<0.01) compared with hay. Confocal microscopy and transmission electron microscopy confirmed that Epidinium spp. were commonly saturated with intracellular cytoplasmic chloroplasts. These data suggest that engulfment of chloroplasts is a major contributor to the high 18:3 (n-3) concentration of protozoa.

Interplay between light intensity, chlorophyll concentration and culture mixing on the hydrogen production in sulfur‐deprived Chlamydomonas reinhardtii cultures grown in laboratory photobioreactors

Relationships between light intensity and chlorophyll concentration on hydrogen production were investigated in a sulfur-deprived Chlamydomonas reinhardtii culture in a laboratory scale photobioreactor (PBR) equipped with two different stirring devices. In the first case, the culture was mixed using a conventional magnetic stir bar, while in the second it was mixed using an impeller equipped with five turbines. Experiments were carried out at 70 and 140 micromol photons m(-2) s(-1) in combination with chlorophyll concentrations of 12 and 24 mg L(-1). A high light intensity (140 micromol photons m(-2) s(-1), supplied on both sides of the PBR) in combination with a low chlorophyll concentration (12 mg L(-1)) inhibited the production of hydrogen, in particular in the culture mixed with the stir bar. An optimal combination for hydrogen production was found when the cultures were exposed to 140 micromol photons m(-2) s(-1) (on both sides) and 24 mg L(-1) of chlorophyll. Under these conditions, the hydrogen production output rate reached about 120 mL L(-1) in the culture mixed with the stir bar, and rose to about 170 mL L(-1) in the one mixed with the impeller. These outputs corresponded to a mean light conversion efficiency of 0.56% and 0.81%, respectively. However, the efficiency increased to 1.08% and 1.64%, respectively, when maximum hydrogen rates were considered. The better performance of the dense cultures mixed with an impeller was mainly attributed to an intermittent illumination pattern to which the cells were subjected (time cycles within 50-100 ms) which influenced the hydrogen production (1) directly, by providing the PSII with a higher production of electrons for the hydrogenase and (2) indirectly, through a higher synthesis of carbohydrates. The fluid dynamics in the PBR equipped with the impeller was characterized. The better mixing state achieved in the PBR of the new configuration makes it a useful tool for studying the hydrogen production process involving photosynthetic microorganisms, and provides a better insight into the physiology of the process.

Reliable cues and signals of fruit quality are contingent on the habitat in black elder (Sambucus nigra)

Communication mediates interactions between organisms and can be based on signals or cues. Signals are selected for their signaling function, whereas cues evolve for reasons other than signaling. To be evolutionarily stable, communication needs to be reliable on average, but the mechanisms that enforce reliability are hotly debated in light of strong environmental influence on signals and cues. While fruit quality in black elder (Sambucus nigra) is unrelated to fruit color, it is indicated by alternative pedicel phenotypes. Information on fruit quality has thus been transferred from the fruit to the developmentally associated pedicels, which are environmentally determined cues. Within each phenotype, color variation indicates fruit quality. Communication by black elder is thus reliable, but the proximate mechanisms enforcing reliability are habitat specific. High irradiance increases both the contrasts of the visual cue and fruit quality in the anthocyanin-based red pedicel phenotype, while shaded plants of the chlorophyll-based green phenotype apparently use signals by forgoing photosynthesis. This is because lower chlorophyll content in green pedicels creates contrasting pedicels, and higher contrasts indicate higher sugar content in the fruits of green pedicels. Because anthocyanins are light-induced, plants use cues when exposed to high irradiance, whereas they apparently use costly signals in the shade by reducing chlorophyll content in the pedicels. In behavioral field and laboratory experiments we document that avian seed dispersers select among pedicel phenotypes that indicate different fruit quality. Plants can thus increase their reproductive success by sending highly informative cues. Our results indicate how reliable information transfer can be maintained both in cues and signals in spite of substantial environmental influence on visual traits.

Detection and differentiation of nitrogen-deficiency, powdery mildew and leaf rust at wheat leaf and canopy level by laser-induced chlorophyll fluorescence

The objective of the present study was to test whether the detection of chlorophyll fluorescence in high frequency multipoint scanning mode may enable identification of nitrogen(N)-deficiency and pathogen infections such as leaf rust (Puccinia recondita) and powdery mildew (Blumeria graminis) in winter wheat. Fluorescence readings at 690 nm (F690) and 730 nm (F730) were taken in the light under constant environmental conditions at leaf and canopy level. In order to identify the sources of heterogeneity of fluorescence signals at canopy level, fluorescence recordings from upper and lower leaf sides were additionally compared. F690/F730 was tendentiously lower on the lower leaf sides in all treatments. Throughout the experiment, N-deficient wheat plants displayed lower chlorophyll content and increased F690/F730 ratio. Pathogen infected plants showed a significantly enhanced fluorescence ratio, associated with chlorophyll degradation in the infected areas, only after appearance of visual symptoms. The results of cross-validation analysis indicated that with chlorophyll fluorescence measurements, samples with pathogen infections may be misrecognised as N deficiency and vice versa. Classification rates of N deficiency and leaf rust could be improved when heterogeneity (standard deviation) of F690 and F730 was considered in addition to the mean as a parameter for discrimination.

Morphological and cytological development and starch accumulation in hermaphrodite and staminate flowers of olive (Olea europaea L.)

In olive (Olea europaea L.), the formation of functionally staminate flowers rather than fully functional hermaphrodites is one of the major factors limiting fruit set, as flowers with aborted pistils are incapable of producing fruit. Studies conducted on various angiosperm species have shown a correlation between flower abortion and starch content. Thus, it is important to know if starch content plays a role in regulating pistil development in olive and if so, what mechanism regulates starch distribution. Cyto-histological observations of staminate and hermaphrodite olive flowers show that pistil development in staminate flowers is interrupted after the differentiation of the megaspore mother cell. At that stage, starch grains were only detected in the ovary, style and stigma of the hermaphrodite flowers. No starch was observed in the pistils of the staminate flowers. This finding suggests a tight correlation between starch content and pistil development. The secondary origin of starch within the flower is indicated by low chlorophyll content in the gynoecium, undetectable Rubisco activity in the pistils of these two kinds of flowers and by the ultrastructure of the plastids observed by transmission electron microscope analysis. The plastids have few thylakoid membranes and grana and in the staminate flowers appeared very similar to proplastids. Considering differences in starch content between staminate and hermaphrodite flowers and the secondary origin of the starch, differences in pistil development in the staminate and hermaphrodite flowers could be related to differences in the sink strength of these two types of flowers.

Gene mapping related to yellow green leaf in a mutant line in rice (Oryza sativa L.)

A mutant, which derived from the restorer line Jinhui10 treated with EMS, showed completely yellow green leaves, and it had low chlorophyll content and poor agronomic characteristics during the growing stage. The F1 plants from the cross between normal × the mutant showed normal green leaves, and the segregation ratio of normal to yellow green leaves was 3 : 1 in F2 population. It indicated that the trait was controlled by a single recessive nuclear gene, temporarily designated asygl3. The geneygl3 was mapped between RM468 and RM3684 with genetic distances 8.4 cM and 1.8 cM on chromosome 3. This result would be used as genetic information for fine mapping and map-based cloning ofygl3 gene.