High Rates Of Photosynthesis Research Articles

Intraspecific variation in morphology, physiology, and ecology of wildtype relative to horticultural varieties of red maple (Acer rubrum)

Wildtype and horticultural varieties of red maple seedlings had different morphologies and physiological responses to water stress and abundances of an insect herbivore when grown in a common garden. Horticultural varieties of trees (cultivars) are selected for desirable and consistent morphologies relative to wildtype trees, but the ways by which morphology influences intraspecific physiological and ecological responses are unclear. In this study, we compared morphology, gas exchange and water use efficiency, and stem herbivory for seedlings of wildtype red maple (Acer rubrum) and two cultivars, ‘Summer Red’ and ‘Brandywine,’ grown together in a common garden. Seedlings also received high and low water treatments. Overall, wildtype seedlings grew taller, had fewer, larger leaves, intermediate rates of photosynthesis, and lower abundances of the scale insect Melanapsis tenebricosa, relative to the cultivars. Summer Red seedlings had more leaves, leaves with red coloration throughout the growing season, and the highest rates of photosynthesis, although photosynthesis was higher in green relative to red leaves. Brandywine seedlings tended to be intermediate in morphology, exhibited smaller differences between the high and low water treatments, and had higher leaf water use efficiency than Summer Red seedlings in April and June but similar water use efficiency in September. Total seedling water use efficiency, measured in September, was highest for wildtype seedlings. Both cultivars had more scale insects than wildtype seedlings under well-watered conditions. These differences among types of red maple aid in understanding how intraspecific variation in tree appearance—and the en masse planting of a single cultivar in cities—affects physiological and ecological responses, the provision of ecosystem services, and the condition of planted trees.

A diurnal carbon engine explains 13C-enriched carbonates without increasing the global production of oxygen

In the past 3 billion years, significant volumes of carbonate with high carbon-isotopic ([Formula: see text]C) values accumulated on shallow continental shelves. These deposits frequently are interpreted as records of elevated global organic carbon burial. However, through the stoichiometry of primary production, organic carbon burial releases a proportional amount of [Formula: see text], predicting unrealistic rises in atmospheric [Formula: see text] during the 1 to 100 million year-long positive [Formula: see text]C excursions that punctuate the geological record. This carbon-oxygen paradox assumes that the [Formula: see text]C of shallow water carbonates reflects the [Formula: see text]C of global seawater-dissolved inorganic carbon (DIC). However, the [Formula: see text]C of modern shallow-water carbonate sediment is higher than expected for calcite or aragonite precipitating from seawater. We explain elevated [Formula: see text]C in shallow carbonates with a diurnal carbon cycle engine, where daily transfer of carbon between organic and inorganic reservoirs forces coupled changes in carbonate saturation ([Formula: see text]) and [Formula: see text]C of DIC. This engine maintains a carbon-cycle hysteresis that is most amplified in shallow, sluggishly mixed waters with high rates of photosynthesis, and provides a simple mechanism for the observed [Formula: see text]C-decoupling between global seawater DIC and shallow carbonate, without burying organic matter or generating O2.

Leaf and whole-plant gas exchange and water-use efficiency of chrysanthemums under HPS and LEDs during the vegetative and flower-induction stages

The effects of light quality on photosynthesis and transpiration of chrysanthemums during the vegetative and flowering stages are not known. Leaf and whole-plant CO2 and H2O exchanges of chrysanthemums during long-day (LD) and short-day (SD) photoperiods were measured under varying intensity levels of high-pressure sodium (HPS) and different monochromatic and multicolour light-emitting diode (LED) lights. All light sources induced leaf photosynthesis effectively, including green and orange LEDs. During both LD and SD, HPS, white, and notably orange light produced high rates of photosynthesis, whereas blue light had the lowest rates. In addition, there were only subtle changes in the response of leaf functions to light quality during flowering induction. Diurnal patterns of whole-plant net C exchange rate were similar under HPS and two commercial LED lights, one red–blue (RB) and one red–white (RW), during both LD and SD. The RB and RW LED lights were as effective at maintaining whole-plant C gain during the day as traditional HPS lights. However, in comparison to HPS, the RB and RW LEDs increased whole-plant transpiration and decreased water-use efficiency (WUE). A decrease in WUE under these LEDs was not evident from the leaf measurements, which emphasizes the importance of examining responses to light quality at the whole-plant level as well and not at the leaf level alone. In commercial production, the wavelength of supplementary lighting may heavily influence WUE and subsequent nutrient uptake, and ultimately growth and quality of cut flower crops.

Diffuse light and wetting differentially affect tropical tree leaf photosynthesis.

Most ecosystems experience frequent cloud cover resulting in light that is predominantly diffuse rather than direct. Moreover, these cloudy conditions are often accompanied by rain that results in wet leaf surfaces. Despite this, our understanding of photosynthesis is built upon measurements made on dry leaves experiencing direct light. Using a modified gas exchange setup, we measured the effects of diffuse light and leaf wetting on photosynthesis in canopy species from a tropical montane cloud forest. We demonstrate significant variation in species-level response to light quality independent of light intensity. Some species demonstrated 100% higher rates of photosynthesis in diffuse light, and others had 15% greater photosynthesis in direct light. Even at lower light intensities, diffuse light photosynthesis was equal to that under direct light conditions. Leaf wetting generally led to decreased photosynthesis, particularly when the leaf surface with stomata became wet; however, there was significant variation across species. Ultimately, we demonstrate that ecosystem photosynthesis is significantly altered in response to environmental conditions that are ubiquitous. Our results help to explain the observation that net ecosystem exchange can increase in cloudy conditions and can improve the representation of these processes in Earth systems models under projected scenarios of global climate change.

Plant economic strategies of grassland species control soil carbon dynamics through rhizodeposition

Abstract The plant economics spectrum is increasingly recognized as a major determinant of plant species effects on terrestrial ecosystem functioning related to carbon cycling. However, the role of plant economic strategies in the effects of living root activity on soil organic carbon (SOC) dynamics through rhizodeposition remains unexplored, despite SOC being the largest terrestrial carbon pool. Using a continuous 13C‐labelling method allowing partitioning of plant and soil sources to carbon fluxes and pools, we studied here the linkages between plant economic strategies and SOC cycling processes in a ‘common garden’ greenhouse experiment. It includes a panel of 12 grassland species selected along a gradient of economic traits and belonging to three functionnal groups (C3 grasses, forbs and legumes). All species induced an acceleration of native SOC mineralization but this rhizosphere priming effect (RPE) substantially differed across species and varied eleven‐fold by the end of the experiment (from +26% to +295% relative to unplanted soil). Interspecific variation in RPE was primarily linked to plant photosynthetic activity associated to species economic strategies of light and CO2 resource acquisition and processing. Fast‐growing acquisitive species, such as legumes, featured large RPE, in relation with their high canopy photosynthesis coupled to high leaf photosynthetic capacity and large net primary productivity allocated above‐ground. This large RPE was further associated with high root metabolic activity, rhizodeposition and soil microbial activity. In contrast, fine‐root growth and economic traits related to soil resource foraging ability were poor predictors of RPE. The formation of new root‐derived SOC varied nine‐fold across species and was similarly positively related to the net primary productivity allocated above‐ground. Fast‐growing acquisitive species with a high photosynthetic activity induced a disproportionately large RPE relative to SOC formation. Synthesis. Overall, our study demonstrates that rhizodeposition is a major mechanism through which plant economic strategies of grassland species control soil carbon dynamics. Acquisitive versus conservative species were associated with high versus low rates of photosynthesis and rhizodeposition, in turn leading to fast versus slow SOC turnover. This emphasizes the importance of considering rhizosphere processes for understanding plant species effects on soil biogeochemistry.

Leaf photosynthesis is mediated by the coordination of nitrogen and potassium: The importance of anatomical-determined mesophyll conductance to CO2 and carboxylation capacity

Both nitrogen (N) and potassium (K) have been widely studied in maintaining efficient photosynthesis and plant growth. However, the mechanisms underlying the photosynthetic response to their interaction remain unclear. This study assessed the effects of N and K supply on photosynthetic limitations and the corresponding changes in anatomical structures in leaves of rice (Oryza sativa L.) plants, grown hydroponically under different levels of N and K in a greenhouse. Results revealed that a suitable leaf N/K ratio (2.99–3.10) maintain a high rate of photosynthesis (A). The A under N and/or K deficiency was primarily limited by mesophyll conductance (gm) and RuBP carboxylation in biochemical processes. The decline of gm in N- or K-starved leaves was mostly resulted from low surface area of chloroplasts exposed to intercellular airspaces (Sc) and high mesophyll cell wall thickness. Synergistic effects of N and K on gm were reflected in leaf anatomical structure, especially their coordinated roles in enhancing Sc. The enhanced photosynthesis in plants with coordinated supply of N and K was caused by the balance of RuBP carboxylation and regeneration. These results highlight the synergistic effect of N and K on leaf photosynthesis, which are mainly reflected in facilitating anatomical-determined gm and carboxylation capacity.

Effect of Different Combinations of Red and Blue LED Light on Growth Characteristics and Pigment Content of In Vitro Tomato Plantlets

The aim of this study was to evaluate the growth characteristics and pigment content of tomato plantlets grown under various ratios of red (R) (661 nm) and blue (B) (449 nm) LED light. In this study, three different ratios of R and B (RB) light such as 5:01, 10:01, and 19:01 along with R (100%) were used. The photosynthetic photon flux density (PPFD), and photoperiod of the growth chamber was 120 ± 5 μmol m−2s−1 and 16/8 h (day/night), respectively. Tomato plantlets were cultured for six weeks in the growth chamber. It was shown that tomato plantlets had higher photosynthesis rate, higher pigments content, higher growth characteristics (e.g., number of leaves, leaf area, shoot number, root number, root length, dry, and fresh mass), and greater surviving rate under the R:B = 10:01 ratio among the treatments. The plantlets showed at least a threefold decrease in photosynthesis rate, as well as a significant abnormal stem elongation when grown under 100% R light. It is concluded that the RB ratio of 10:01 showed excellent performance in all growth parameters. This result has shown that the optimum lighting environment improves tomato plantlet cultures in vitro.

Evaluation of water-saving rice status based on morphophysiological characteristics and water use efficiency

Abstract. Darmadi D, Junaedi A, Sopandie D, Supijatno, Lubis I, Homma K, Hidayati N. 2019. Evaluation of water-saving rice status based on morphophysiological characteristics and water use efficiency. Biodiversitas 20: 2815-2823. One strategy to anticipate water shortages in rice production is to use varieties that are efficient in using water and produce high yields. The aim of this study was to measure water consumption, water use efficiency and production performance of several types of rice. The research was conducted during the rainy season from January to April 2018 and the dry season from August to November 2018 in a greenhouse. This study used a completely randomized design. The genetic materials used were 8 varieties consisting of lowland rice (sawah), upland rice (gogo), and land race. The variables analyzed included morphological and physiological characteristics. The results showed that differences in rice types indicated diverse responses to morphological and physiological characteristics on water consumption and water use efficiency (WUE). Mentik Wangi variety had the highest water consumption of 24.1 liters. The IPB 9 G and Jatiluhur varieties achieved the highest water use efficiency of 2.4 and 2.3, respectively. Based on the heatmap analysis, both varieties had similarities in the morphological characteristics of long roots, high root weights, long and broad leaves, and high total grain counts per panicle. The similarity of physiological characteristics was high rates of photosynthesis and low transpiration. Varieties that achieve the highest water use efficiency have the potential to be developed into varieties that are tolerant to limited water conditions.

Integrating Morphological and Physiological Responses of Tomato Plants to Light Quality to the Crop Level by 3D Modeling.

Next to its intensity, the spectral composition of light is one of the most important factors affecting plant growth and morphology. The introduction of light emitting diodes (LEDs) offers perspectives to design optimal light spectra for plant production systems. However, knowledge on the effects of light quality on physiological plant processes is still limited. The aim of this study is to determine the effects of six light qualities on growth and plant architecture of young tomato plants, and to upscale these effects to the crop level using a multispectral, functional-structural plant model. Young tomato plants were grown under 210 μmol m-2 s-1 blue, green, amber, red, white or red/blue (92%/8%) LED light with a low intensity of sunlight as background. Plants grown under blue light were shorter and developed smaller leaves which were obliquely oriented upward. Leaves grown under blue light contained the highest levels of light harvesting pigments, but when exposed to blue light only, they had the lowest rate of leaf photosynthesis. However, when exposed to white light these leaves had the highest rate of photosynthesis. Under green light, tomato plants were taller and leaves were nearly horizontally oriented, with a high specific leaf area. The open plant structure combined with a high light transmission and reflection at the leaf level allowed green light to penetrate deeper into the canopy. Plants grown under red, amber and white light were comparable with respect to height, leaf area and biomass production. The 3D model simulations indicated that the observed changes in plant architecture had a significant impact on light absorbance at the leaf and crop level. The combination of plant architecture and spectrum dependent photosynthesis was found to result in the highest rate of crop photosynthesis under red light in plants initially grown under green light. These results suggest that dynamic light spectra may offer perspectives to increase growth and production in high value production systems such as greenhouse horticulture and vertical farming.

High mesophyll conductance in the high-yielding rice cultivar Takanari quantified with the combined gas exchange and chlorophyll fluorescence measurements under free-air CO2 enrichment

ABSTRACTAn effective strategy for increasing crop production is increasing the rate of photosynthesis. In this study, we conducted gas exchange and chlorophyll fluorescence measurements for a high-yielding rice cultivar, Takanari, to identify the leaf physiological properties that contribute to high capacity for photosynthesis of the uppermost leaves before (panicle initiation stage) and after heading (grain-filling stage) in the Tsukuba free-air CO2 enrichment (FACE) facility. The higher photosynthesis rate of Takanari compared with that of the commonly cultivated cultivar, Koshihikari, was mainly attributed to the greater stomatal conductance for CO2 (gsc) at the panicle initiation stage and to the greater mesophyll conductance (gm) at the grain-filling stage in both current and elevated atmospheric CO2 concentrations [CO2]. Takanari had a higher level of leaf nitrogen content (Nl) compared with Koshihikari at the grain-filling stage, which led to greater gm and maximum carboxylation rate (Vc,max), but Nl alone did not explain the variations of gm within the variety. A clear correlation was found between Vc,max and Nl. Calculating Vc,max taking gm into consideration removed the artifact of Vc,max25 in relation to Nl that was observed when gm was assumed to be infinite. Our results emphasize the need to separate the roles of Vc,max and gm to accurately understand the ecophysiological processes that control leaf photosynthesis in Takanari.

Improve Plant Photosynthesis by a New Slow-Release Carbon Dioxide Gas Fertilizer.

In the natural state, the concentration of carbon dioxide in the atmosphere is about 300 μmol mol–1. Plants need a suitable balance of CO2 to achieve optimal growth. The optimum CO2 content corresponding to a high photosynthesis rate is between 0.1 and 1.0% by volume. However, air has only a CO2 content of 0.03% by volume, so plants cannot use all of their growth potential. The use of fertilizer to assist in the supply of CO2 increases the rate of photosynthesis. In this work, a slow-release CO2 gas fertilizer inspired by polyphenol chemistry was prepared to provide sustainable CO2 that could improve plant photosynthetic capacity and get a higher crop yield. The core–shell structure was designed to confer gas fertilizers slow-release property. Micron-sized calcium carbonate particles with uniform particle size and regularity morphology, as carbon sources for plant photosynthesis, was a core, and tannic acid was coated on it as a shell via oxidative oligomerization and cross-linked by polyetherimide. The structure and morphology of fertilizers were characterized by scanning electron microscopy, X-ray energy dispersive spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. In vitro experiments, the prepared fertilizers were proved to have slow-release properties. And then through net photosynthesis rate, chlorophyll fluorescence parameters, chlorophyll content, leaf area, leaf mass per area, and dry matter to study the effects of slow-release CO2 gas fertilizers on plant physiology of Brassica chinensis. The results revealed that the slow-release CO2 gas fertilizers not only had good slow-release properties but also can well improve plant photosynthesis.

Application of water-saving treatments reveals different adaptation strategies in three Iranian melon genotypes

Melon is a major horticultural crop in Iran, where it is grown in semi-arid areas in irrigated fields. Concerns about future water security stimulate the development of water-saving irrigation practices, which requires a better understanding of melon physiology under reduced water supply. To this end, one variety of muskmelon, “Samsoury”, and two varieties of the Dudaim group, “Birjand” and “Kerman”, were grown in pots in a greenhouse with three water management treatments, consisting in refilling soil water to field capacity at different intervals: three days (T3), six days (T6) and nine days (T9). Leaf water status declined when longer refilling intervals were applied, but all genotypes maintained the same leaf turgor pressure irrespective of the treatment. Turgor was maintained both through osmotic adjustment (OA) and change in cell wall elasticity. Samsoury showed the highest OA in T3 and T6, while variation in cell wall elasticity was more evident in Birjand and Kerman. Samsoury showed also the highest photosynthesis rate (An) and stomatal conductance (gs) in T3 and T6, but the three genotypes exhibited similar values in T9. In the Dudaim-types An and gs declined linearly as soon as water potential started to decrease, while Samsoury was able to keep gas-exchange parameters stable down to a water potential value of –11.5 bars, to steeply decrease thereafter. Finally, Samsoury had the least reduction in biomass allocated to epigeic part, and allocated a higher proportion of biomass to roots in response to water restriction. From all the results, it is concluded that Samsoury performs better when water-saving treatments allow low to moderate water stress, thanks to its anisohydric-like behaviour, consisting in a looser coupling of stomatal closure with water potential, which ensures higher carbon accumulation under fluctuating water supply. The Dudaim-types showed instead a rather more conservative behaviour, typical of isohydric plants, which privilege water loss avoidance even at low water restriction levels, at the cost of carbon assimilation and growth.

Urea Is Both a Carbon and Nitrogen Source for Microcystis aeruginosa: Tracking 13C Incorporation at Bloom pH Conditions.

The use of urea as a nitrogenous fertilizer has increased over the past two decades, with urea itself being readily detected at high concentrations in many lakes. Urea has been linked to cyanobacterial blooms as it is a readily assimilated nitrogen (N) - source for cyanobacteria that possess the enzyme urease. We tested the hypothesis that urea may also act as a carbon (C) source to supplemental growth requirements during the alkaline conditions created by dense cyanobacterial blooms, when concentrations of dissolved CO2 are vanishingly low. High rates of photosynthesis markedly reduce dissolved CO2 concentrations and drive up pH. This was observed in Lake Erie during the largest bloom on record (2015) over long periods (months) and short periods (days) of time, suggesting blooms experience periods of CO2-limitation on a seasonal and daily basis. We used 13C-urea to demonstrate that axenic cultures of the model toxic cyanobacterium, Microcystis aeruginosa NIES843, assimilated C at varying environmentally relevant pH conditions directly into a spectrum of metabolic pools during urea hydrolysis. Primarily, 13C from urea was assimilated into central C metabolism and amino acid biosynthesis pathways, including those important for the production of the hepatotoxin, microcystin, and incorporation into these pathways was at a higher percentage during growth at higher pH. This corresponded to increased growth rates on urea as the sole N source with increasing pH. We propose this ability to incorporate C from urea represents yet another competitive advantage for this cyanobacterium during dense algal blooms.

Enhanced biomass and lipid production of Neochloris oleoabundans under high light conditions by anisotropic nature of light-splitting CaCO3 crystal

The aim of this work was to study the anisotropic effect of crystalline CaCO3 nanoparticles (CN)-driven multiple refraction/scattering from the CN-coated agglomerated cells on the rate of photosynthesis and the product yield under high light conditions in the freshwater microalgae Neochloris oleoabundans. The CN-coating via biomineralization significantly improved the biomass and lipid production of N. oleoabundans during second stage of autotrophic induction by sustaining relatively high rate of photosynthesis at high irradiance using the multiple-splitting effect of the anisotropic polymorphism. The CN were successfully produced, adsorbed and grown on the external cells under conditions of mild alkalinity (pH 7.5–8.0), mild CaCl2 concentration (0.05 M) and under nitrogen starvation with strong light (400 µE m−2 s−1). Consequently, lipid content and productivity of N. oleoabundans cells cultured with 0.05 M CaCl2 increased by 18.4% and 31.5%, respectively, compared to the cells cultured with 0.05 M CaCl2 and acetazolamide to inhibit calcification.

Differences in photosynthetic and transpiration activity of bine and branch leaves of hop plant (Humulus lupulus L.)

This paper evaluates photosynthetic and transpiration rate of bine and branch leaves of hop (cultivar 'Agnus'). Monitoring of photosynthetic rate helps us determine phases of vegetation and environmental conditions under which plants are most active, most productive, or what influences their activity. By measuring, using LC pro+ (ADC Bio Scientific Ltd.), we detected that branch leaves show a higher rate of photosynthesis than bine leaves. Branch leaves' photosynthetic rate in the period 2011-2013 ranged between 120-184% compared with bine leaves. However, we did not find any dependence of yield on the rate of photosynthesis during the experiment. In some years when lower photosynthetic rate was measured, higher yields were achieved than in years with higher photosynthetic activity. Yield formation is therefore a multifactorial complex, involving main influence of year and weather conditions. Photosynthetic rate of bine leaves ranged from 3.29 to 8.33 μmol CO2 m(-2) s(-1). Photosynthetic rate of branch leaves ranged from 6.05 to 9.89 μmol CO(2) m(-2) s(-1). Transpiration rate of branch leaves ranged between 104-119% compared with bine leaves.

Expression of a Small Ubiquitin-Like Modifier Protease Increases Drought Tolerance in Wheat (Triticum aestivum L.).

Post-translation modification of proteins plays a critical role in cellular signaling processes. In recent years, the SUMO (Small Ubiquitin-Like Modifier) class of molecules has emerged as an influential mechanism for target protein management. SUMO proteases play a vital role in regulating pathway flux and are therefore ideal targets for manipulating stress-responses. In the present study, the expression of an Arabidopsis thaliana cysteine protease (OVERLY TOLERANT TO SALT-1, OTS1) in wheat (Triticum aestivum L.) has led to improved plant growth under water stress conditions. Transformed wheat (pUBI-OTS1) displayed enhanced growth and delayed senescence under water deficit when compared with untransformed Gamtoos-R genotype or plants carrying an empty vector. Transformed pUBI-OTS1 plants also maintained a high relative moisture content (RMC), had a higher photosynthesis rate, and also had a higher total chlorophyll content when compared to untransformed plants or plants carrying an empty vector. SUMOylation of total protein also increased in untransformed plants but not in the AtOTS1 transformed plants. Our results suggest that SUMO-proteases may influence an array of mechanisms in wheat to the advantage of the crop to be more tolerant to water stress caused by drought. This is the first report to elucidate SUMOylation effects in the hexaploid crop wheat (T. aestivum L.).

Short-term physiological responses to drought stress in seedling of tropical and temperate maize (Zea mays L.) cultivars

Understanding of the response of tropical and temperate maize (Zea mays L.) to drought is the first step for tolerant temperate maize improvement. Eight maize hybrids were used to investigate physiology responses under drought stress, four of them were tropical maize and the others were temperate maize. Results showed that there were different drought tolerances but similar trends in both tropical maize and temperate maize. Gas exchange parameters revealed different strategies of maize under the stress. In our study, most of the temperate hybrids maintained open stomata to keep a higher photosynthesis rate at the beginning of stress, while the other hybrids decreased stomatal conductance. Compared to temperate maize, the tropical maize had higher antioxidase activity and greater physiological parameter variation among hybrids. KS5731 and ZD309 had stronger drought resistance among tropical and temperate maize hybrids separately. Tolerant hybrids maintained active photosynthesis, have higher osmotic adjustment ability and antioxidase activities but lower malonaldehyde content than the sensitive ones. Our results led to a better understanding of the physiological responses of tropical and temperate maize plants to drought stress and may provide an insight of breeding for drought resistance in maize.

Improving field establishment of cacao (Theobroma cacao) through mulching, irrigation and shading

AbstractEstablishment of young cacao trees in West Africa can be severely impeded by the onset of the dry season. To address this issue, a field experiment was conducted in Ghana to examine whether different mulch treatments and irrigation applied during the dry season combined with overhead shade could improve survival, early growth and yield of cacao. The mulch treatments used were polyethylene film and coffee husks placed around the young plants. Irrigation was used as a positive control, and no mulching or irrigation was a negative control. Three shade regimes were provided through different arrangements ofGliricidia sepiumand plantains. Four different cacao clones were used in the study in a replicated split-plot design. Early growth of cacao was stimulated under the irrigation and plastic mulch treatments. Higher rates of photosynthesis during the dry season appeared to underlie these increases. Significantly higher early yields were also observed under the irrigation and coffee mulch treatments compared with the control. Plant survival varied significantly between treatments; irrigation was associated with the highest plant survival (94%), followed by the plastic mulch treatment (91%), coffee husk (82%) and the control (70%). There was also an increase in survival when more intense shading was used. Under zero mulch conditions, differences in survival were observed between clones. The clones P 30 [POS] and SCA 6 were more sensitive to drought (in terms of survival) than PA 150 and T 79/501. It is concluded that relatively simple mulching techniques or controlled irrigation in conjunction with appropriate shade management can significantly improve early establishment and cropping of cacao.

Studies on rejuvenation of old and senile orchards of Alphonso mango in Konkan region of Maharashtra

Alphonso is the premier mango variety owing to its excellent flavour, aroma, colour and shelf life. It constitutes more than 90 per cent of area 1.82 Lakh hectares of the mango in Konkan region. Majority of orchards are old and senile with low productivity. The attempts were therefore made to develop and standardize the rejuvenation technology for such mango orchards. An experiment was conducted on 40 years old senile mango orchard of mango cv. Alphonso from 2011 to 2015 with two treatments viz., T1-Rejuvenated plants and T2-Non-Rejuvenated plants replicated 13 times in randomized block design. The observations viz., twig girth (cm), avg. leaf area (cm2), rate of photosynthesis (μ mol CO2/m2/sec), rate of respiration (μ mol CO2/m2/sec), length of panicle (cm), breadth of panicle (cm), hermaphrodite flowers (%), number of fruits per plant, yield per plant (kg) and yield per hectare (t) were recorded on both rejuvenated and non-rejuvenated plants from 2013–14 to 2015–16. The rejuvenation technology was also demonstrated on farmers’ field at Katta, Adeli, Nadan in Sindhudurg district and Asore and Mazgaon in Ratnagiri district. High rate of photosynthesis, high hermaphrodite flower percentage (%), more fruits per plant with better fruit weight and higher yield (per plant and per hectare) were recorded in rejuvenated plants as compared to non-rejuvenated plants. The chemical composition of the fruits viz., T.S.S, acidity, Total sugars and reducing sugars were non-significant. Due to rejuvenation there was appreciable reduction in the use of quantity of insecticide, fungicide and human labour in rejuvenated plants. The performance of rejuvenated plants on farmer's field was also better than non-rejuvenated plants.

Influence of water stress on grape quality and aroma precursors in Sauvignon Blanc grown in Bolgheri area (Tuscany)

Climate change has a direct impact on the phenological stages of the grapevine, with consequences on the anticipation of aging and on the qualitative characteristics of the grapes. In fact, there is a decrease in the skin/pulp ratio, with possible reduction of the aromatic potential. This work was aimed at assessing the effects of water stress on technological maturity and thiol precursors of Sauvignon Blanc grapes in two vineyards of Bolgheri. To this purpose, 3 theses have been established: WW, well watered; WS, moderate stress; CTRL, control. During the season, measurements of single leaf gas exchange, stem water potential were made; moreover parameters of technological maturity (° Brix, acidity, pH and berry weight) and thiol precursors were analyzed. As expected, the water potential was less negative in the irrigated thesis due to the greater availability of water, as well as the highest rates of photosynthesis, transpiration and stomatal conductance. Technological analyses showed no significant differences among the treatments. The analysis of the 3MH/3-mercaptoesan-1-ol precursors showed that the WW had a greater accumulation than the other theses. These results suggest that lower water stress favors a better aromatic content.