Plants In Full Sun Research Articles

Influence of integrated crop-livestock-forest on morphological composition and nutritional value of Marandu palisadegrass under continuous grazing

This study characterizes the changes in leaf mass, morphological composition and nutritional value of leaf blades of palisadegrass (Urochloa brizantha cv. Marandu) under continuous grazing in the first year of implementation of pasture and after second year of the eucalyptus planting in an Integrated Crop-Livestock System and Integrated Crop-Livestock-Forest, which were tested in the four seasons. The experimental design was in random blocks, with three treatments: Crop-Livestock System (ICL) and Integrated Crop-Livestock-Forest with two eucalyptus tree densities (ICLF-1L, 196 eucalyptus trees ha-1 and ICLF-3L, 448 eucalyptus trees ha-1) and four replicates. Sixty castrated Nellore cattle with initial weight of 235.43 ± 25.46 kg and mean age of 16 ± 2.81 months were used during the growing phase under continuous grazing. The agronomic variables were: total dry mass of forage, leaves, stem and dead material; leaf: stem and live: senescent material ratios; and accumulation rate. The leaf: stem and live: senescent material relation did not obtain any difference between the evaluated systems. Dry matter, crude protein, fiber fractions and digestibility of leaf blades were evaluated. Dry mass of the forage (6775 kg ha-1), stem (2175 kg ha-1), senescent material (3175 kg ha-1) and dry matter content (28.6%) were greater in the ICL, whereas crude protein (11.3%) was greater in the ICLFs. On the other hand, accumulation rate and dry mass of leaf blades did not change between systems. Thus, until the first year of grazing, tree systems have advantages, because the forage production (accumulation rate) and leaf mass are similar to those of plants in full sun, besides showing higher nutritional value.

Concurrent starch accumulation in stump and high fruit production in coffee (Coffea arabica).

In coffee, fruit production on a given shoot drops after some years of high yield, triggering pruning to induce resprouting. The timing of pruning is a crucial farmer's decision affecting yield and labour. One reason for fruit production drop could be the exhaustion of resources, particularly the non-structural carbohydrates (NSC). To test this hypothesis in a Coffea L. arabica agroforestry system, we measured the concentrations of NSC, carbon (C) and nitrogen (N) in leaves, stems and stumps of the coffee plants, 2 and 5years after pruning. We also compared shaded vs full sun plants. For that purpose, both analytical reference and visible and near infrared reflectance spectroscopy (VNIRS) methods were used. As expected, concentrations of biochemical variables linked to photosynthesis activity (N, glucose, fructose, sucrose) decreased from leaves to stems, and then to stumps. In contrast, variables linked more closely to plant structure and reserves (total C, C:N ratio, starch concentration) were higher in long lifespan organs like stumps. Shading had little effect on most measured parameters, contrary to expectations. Concentrations of N, glucose and fructose were higher in 2-year-old organs. Conversely, starch concentration in perennial stumps was three times higher 5years after pruning than 2years after pruning, despite high fruit production. Therefore, the drop in fruit production occurring after 5-6years was not due to a lack of NSC on plant scale. Starch accumulation in perennial organs concurrently to other sinks, such as fruit growth, could be considered as a 'survival' strategy, which may be a relic of the behaviour of wild coffee (a tropical shade-tolerant plant). This study confirmed that VNIRS is a promisingly rapid and cost-effective option for starch monitoring (coefficient of determination for validation, R2val=0.91), whereas predictions were less accurate for soluble sugars, probably due to their too similar spectral signature.

Coffea arabica L. genes from isoprenoid metabolic pathways are more expressed in full sun cultivation systems than in agroforestry systems

Coffee synthesizes two unique isoprenoid diterpenes, cafestol (C20H28O3) and kahweol (C20H26O3), ent-kaurene compounds produced through the mevalonate or mevalonate-independent pathway. These compounds are relevant to beverage quality, plant defense, human health and nutraceutical properties. We investigate the expression profile of genes in the early (CaHMGR, CaMVD, CaDXR and CaIDS) and final steps of isoprenoid diterpenes biosynthesis (Coffea arabica L. cytochrome P450s: CaCYP82C2, CaCYP71A25, CaCYP74A1 and CaCYP701A3) in two fruits development stages (90 and 210 days after flowering). We also observed total lipid, cafestol and kahweol accumulation in C. arabica grown using two crop systems (full sun and agroforestry) at IDR-Parana Londrina, PR, Brazil. Plants in full sun presented higher gene expression than plants grown in agroforestry systems, except for CaHMGR. Fruits showed higher levels of transcript activity 210 days after flowering, about 2.8 times more in the genes expressed during the first steps and 3.6 times in those in the later steps. Although lipid, cafestol and kahweol were higher in the full sun than the agroforestry system, only increased lipid content was statistically significant. Cultivation system plays an important role in the expression of the genes, particularly as regards light incidence.

Tradeoffs in the evolution of plant farming by ants

Diverse forms of cultivation have evolved across the tree of life. Efficient farming requires that the farmer deciphers and actively promotes conditions that increase crop yield. For plant cultivation, this can include evaluating tradeoffs among light, nutrients, and protection against herbivores. It is not understood if, or how, nonhuman farmers evaluate local conditions to increase payoffs. Here, we address this question using an obligate farming mutualism between the ant Philidris nagasau and epiphytic plants in the genus Squamellaria that are cultivated for their nesting sites and floral rewards. We focused on the ants' active fertilization of their crops and their protection against herbivory. We found that ants benefited from cultivating plants in full sun, receiving 7.5-fold more floral food rewards compared to shade-cultivated plants. The higher reward levels correlated with higher levels of crop protection provided by the ants. However, while high-light planting yielded the greatest immediate food rewards, sun-grown crops contained less nitrogen compared to shade-grown crops. This was due to lower nitrogen input from ants feeding on floral rewards instead of insect protein gained from predation. Despite this tradeoff, farming ants optimize crop yield by selectively planting their crops in full sun. Ancestral state reconstructions across this ant-plant clade show that a full-sun farming strategy has existed for millions of years, suggesting that nonhuman farmers have evolved the means to evaluate and balance conflicting crop needs to their own benefit.

Rescue strategies for Xylopia sericea A.St.-Hil. plants from natural regeneration

The objective of this study was to test different rescue strategies of Xylopia sericea plants from natural regeneration. Two experiments were conducted in a completely randomized design, in split-plots, with the first one consisting of four levels of shading (0 or full sun, 30, 50 and 70% of shading) and four substrates; and the second consisting of four levels of shading and three leaf reduction intensities (0, 50 and 100%). After 150 days from the rescue, the survival and increments in height and diameter were obtained. The general mean survival was 26.1% in the first experiment and 26.7% in the second one. In both experiments the plants in full sun resulted in 100% mortality, while the 70% shading showed to be more effective concerning the survival and in the growth resumption. It is recommended to use substrates whose mixture has at least 50% subsoil as one of its components. Overall, the results obtained by leaf reduction were not sufficient to justify and recommend this procedure, taking into account the increase of the process total costs.

Strong Solar Irradiance Reduces Growth and Alters Catechins Concentration in Tea Plants over Winter

An experiment was conducted to investigate the effect of sunlight and chilling on growth, photosynthesis and chemical composition of tea plants growing in South Korea. The plants were grown in full sun (mid-day photosynthetic photon flux density, PPFD of 563 μmol-2s-1), slight shade (PPFD of 99 μmol-2s-1) or heavy shade (HS, PPFD of 5 μmol-2s-1) in a field at the foot of pine forest from October to March, 2012. Mean and minimum daily temperature fell below 0 °C in December and January. Shading had a small or no effect on shoot and leaf growth. Shading increased the concentration of chlorophyll compared with plants in full sun, with relatively stable values within a treatment over time. Shading increased chlorophyll fluorescence, with lower values in all treatments in late January. The concentration of total catechins was lower under shading, and lower in early January. Low temperatures appear to decrease chlorophyll fluorescence independently of light levels. Growth under heavy shade was dependently of stored reserves and would be unsustainable over the long term. Overall quality as reflected by the concentration of catechins was best under full sun conditions.

Diurnal Serianthes nelsonii Merr. leaflet paraheliotropism reduces leaflet temperature, relieves photoinhibition, and alters nyctinastic behavior

The diel cycle of Serianthes nelsonii leaflet movements was characterized under four levels of shade from full sun to 22% sunlight transmission to determine the photoprotective components of diurnal leaflet movements and the relationship to patterns of nocturnal leaflet movements. Treatments also included negating paraheliotropism by re-orienting plants every 15min throughout the photoperiod such that the plants never experienced a predictable solar vector. The timing of leaflet closure to avoid high light, the shape of the diurnal curve depicting leaflet angle, and the maximum extent of leaflet closure were influenced by the shade treatments. Protection of leaf function by paraheliotropism was also influenced by shade treatment, with the full sun plants exhibiting the greatest level of protection. Leaflet heat gain was reduced 50% by leaflet movement as determined by direct measurements of leaf-to-air temperature differences. Midday quantum efficiency of photosystem II was increased 120% by leaflet movement as determined by direct measurements of pulse modulated chlorophyll fluorescence. The extent of nyctinastic leaflet closure was greatest in the high light plants that moved the most midday and least in the shaded plants that moved the least midday, indicating the extent of diurnal paraheliotropism controlled the amplitude of nocturnal leaflet movement. Serianthes nelsonii is highly skilled at using movement to reduce leaflet exposure to the solar vector, providing instantaneous behavioral control over heat gain and photoinhibition. This case study of an endemic tree species in Micronesia has added to the nascent field of conservation physiology, and indicated that heliotropism of S. nelsonii leaves may provide the species with the ability to minimize high light damage during increased temperatures associated with climate change.

Production of Three Eastern U.S. Native Shrubs: Effects of Auxin Concentration on Rooting and Shade Level on Container Plant Growth

American fly honeysuckle (Lonicera canadensis), hobblebush (Viburnum lantanoides), and sweetbells (Eubotrys racemosa) are eastern U.S. native shrubs with ornamental value, which might become successful nursery crops if they propagate readily from stem cuttings and grow uniformly in containers. We evaluated rooting success for hobblebush and sweetbells using stem cuttings treated with indole-3-butyric acid (IBA) in talc at concentrations of 0, 1000, 3000, or 8000 ppm. For hobblebush, IBA at 1000, 3000, or 8000 ppm will yield 70% rooting success. For sweetbells, IBA treatment did not enhance rooting, and 88% rooting success can be achieved with untreated cuttings. Stem cuttings of american fly honeysuckle root at 49% (previously published). We also evaluated all three native shrubs grown in nursery trade #1 containers under shade levels of 0%, 40%, or 70%. American fly honeysuckle grown under 40% or 70% shade were larger, had a greener hue angle, and higher chlorophyll fluorescence (Fv/Fm) than plants grown in full sun. Throughout the study period, Fv/Fm values for full-sun american fly honeysuckle were 0.6 or below, indicating plants were stressed. Hobblebush in 40% and 70% shade were wider, had more leaves, and enhanced foliage color compared with full-sun plants. Hobblebush in 70% had the highest Fv/Fm values at 0.78 or higher across the study period. For sweetbells, plant width increased as shade level increased. Even though sweetbells in 70% shade were wider and larger, they lacked density and had a less appealing habit than 40% shade and full-sun plants. Of the three study species, sweetbells might be the easiest plant for growers to incorporate into production because it propagates readily from stem cuttings and can be grown in full sun to 40% shade. Hobblebush and american fly honeysuckle may present more challenges for growers because hobblebush requires considerable shade to grow and american fly honeysuckle is more difficult to propagate.

The nocturnal larvae of a specialist folivore prefer Chromolaena odorata (L.) foliage from a sunny environment, but does it matter?

Increasing evidence suggests that the responses of insect herbivores to environment-mediated changes in the phenotypic and phytochemical traits of their host plants are more complex than previously thought. Here, we examined the effects of habitat conditions (shaded versus full-sun habitats) on plant traits and leaf characteristics of the invasive alien plant, Chromolaena odorata (L.) (Asteraceae). We also determined neonate larval preference of the specialist herbivore, Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Erebidae) (a biological control agent) for shaded versus full-sun leaves. The study further evaluated the performance of the moth on C. odorata leaves obtained from both shaded and full-sun habitats. Leaves of C. odorata plants growing in the shaded habitat had higher water and nitrogen contents compared with full-sun leaves. Plants growing in shade had longer leaves but full-sun plants were taller and had greater aboveground biomass compared with shaded plants. Although neonate larvae of P. pseudoinsulata preferred to feed on full-sun foliage, development was faster when reared on shaded foliage. However, survival, pupal mass, growth rate, and Maw’s host suitability index of the moth did not significantly differ between full-sun and shaded foliage. Our inability to demonstrate significant differences in key insect performance metrics in P. pseudoinsulata between shaded and full-sun foliage, despite neonate larval preference for one of the foliage types, suggests that neither of the foliage types can be considered a superior host, and reiterate the fact that relationships between host plant quality (modulated by light intensity) and phytophagous insect performance are not simple.

Exacerbation of photosynthetic damage through increased heat–light stress resulting from Gargaphia decoris sap-feeding

Solanum mauritianum (Bugweed) is one of the world’s worst ecological weeds, being targeted for biological control in South Africa since 1984. One of two promising biocontrol agents released against S. mauritianum is a sap-sucking lace bug, Gargaphia decoris (Hemiptera: Tingidae). There are few studies on physiological changes induced by feeding damage of biological control agents on their target weeds. Chlorophyll removal by G. decoris feeding caused metabolic impairment which resulted in a reduction of photosynthetic rates of S. mauritianum leaves, with a greater effect on plants growing in full sun compared to plants growing in shade. This difference was related to higher leaf temperatures in the sun. Herbivory caused a 52% reduction in transpiration rates, resulting in a reduction in evaporative cooling of the leaf. Although G. decoris’s feeding rates were greater on the shade plants, feeding per unit area was significantly more damaging to plants continually exposed to sunlight. The increased physiological damage experienced by full-sun plants may be a combination of stresses, particularly the direct effect of chlorophyll removal via herbivory and the indirect effect of accumulated heat–light stress. Given G. decoris’s effectiveness for biological control, factors constraining its performance in the field need to be identified and addressed.

Tolerancia a la sombra en plantas de caléndula (Calendula officinalis)

Pot marigold ( Calendula officinalis L.) is the second most commonly-sold medicinal herb in Colombia. The study was performed in Tunja, Colombia, in which chlorophyll and carotenoid content were evaluated in pot marigold grown under low and high light conditions (35% and 100% of full daylight). Chlorophyll fluorescence parameters and electron transport rate were also evaluated. Compared to full sun plants, shaded plants had a higher ratio of chlorophyll a to chlorophyll b, and a lower ratio of carotenoids to chlorophyll. Values for maximum fluorescence ( Fm ), variable fluorescence ( Fv ), and maximum quantum efficiency of photosystem II (the ratio Fv/Fm ) increased in shaded plants, while electron transport rate was reduced. These results suggest that pot marigold plants are very sensitive to low-light conditions.

Relationship Between Woody Plant Colonization and Typha L. Encroachment in Stormwater Detention Basins

We studied stormwater detention basins where woody vegetation removal was suspended for 2 years in Virginia, USA to determine if woody vegetation can control Typha populations and how early woody plant succession interacts with Typha, other herbaceous vegetation, and site factors. Distribution and composition of woody vegetation, Typha and non-Typha herbaceous vegetation biomass, and site factors were assessed at 100 plots in four basins ranging in age from 7 to 17 years. A greenhouse study examined the interaction of shade and soil moisture on Typha biomass and persistence. Principal component analysis identified an environmental gradient associated with greater water table depths and decreased elevation that favored Typha but negatively influenced woody vegetation. Elevation was correlated with litter layer distribution, suggesting that initial topography influences subsequent environmental characteristics and thus plant communities. Soil organic matter at 0-10 cm ranged from 5.4 to 12.7%. Woody plants present were native species with the exception of Ailanthus altissima and Pyrus calleryana. In the greenhouse, shade and reduced soil moisture decreased Typha biomass and rhizome length. The shade effect was strongest in flooded plants and the soil moisture effect was strongest for plants in full sun. Typha in dry soil and heavy shade had 95% less total biomass and 83% smaller rhizomes than Typha in flooded soil and full sun, but even moderate soil moisture reductions decreased above- and below-ground biomass by 63 and 56%, respectively. Suspending maintenance allows restoration of woody vegetation dominated by native species and may suppress Typha invasion.

Influência do sombreamento na qualidade de mudas de Sclerolobium paniculatum Vogel para recuperação de área degradada

O conhecimento do comportamento das espécies florestais em áreas com diferentes intensidades de luz permite a definição e recomendação das espécies no processo de recuperação. Assim, objetivou-se verificar a influência do sombreamento na qualidade das mudas de Sclerolobiumpaniculatum Vogel em projetos de restauração de áreas degradadas. O experimento foi conduzido como delineamento em blocos casualizados, com 15 repetições. Os tratamentos consistiram em três níveis de brilho (T1: 0%, pleno sol, T2: 50%, Sombrite com retenção de 50% da luz e T3: Shadow Natural). As plantas cultivadas em um ambiente com 50% de luz solar apresentaram uma taxa de crescimento em altura (β2: 0,0266) 40% maior que as plantas em pleno sol (β2: 0,0161), principalmente na avaliação de 103 dias. Sob sombreamento natural, a taxa de desenvolvimento mais baixa foi registrada ao longo do período avaliado, representando apenas 5,43% (β2: 0,0193) da taxa de desenvolvimento de plantas sob luz solar total (β2: 0,3557). O aumento da intensidade da luz favorece o maior desenvolvimento de Sclerolobiumpaniculatim Vog. Com isso, pode ser indicado para uso em projetos voltados à recuperação de áreas degradadas no pioneiro da sucessão inicial e no secundário secundário.

Attenuation of the Jasmonate Burst, Plant Defensive Traits, and Resistance to Specialist Monarch Caterpillars on Shaded Common Milkweed (Asclepias syriaca)

Plant responses to herbivory and light competition are often in opposing directions, posing a potential conflict for plants experiencing both stresses. For sun-adapted species, growing in shade typically makes plants more constitutively susceptible to herbivores via reduced structural and chemical resistance traits. Nonetheless, the impact of light environment on induced resistance has been less well-studied, especially in field experiments that link physiological mechanisms to ecological outcomes. Accordingly, we studied induced resistance of common milkweed (Asclepias syriaca, a sun-adapted plant), and linked hormonal responses, resistance traits, and performance of specialist monarch caterpillars (Danaus plexippus) in varying light environments. In natural populations, plants growing under forest-edge shade showed reduced levels of resistance traits (lower leaf toughness, cardenolides, and trichomes) and enhanced light-capture traits (higher specific leaf area, larger leaves, and lower carbon-to-nitrogen ratio) compared to paired plants in full sun. In a field experiment repeated over two years, only milkweeds growing in full sun exhibited induced resistance to monarchs, whereas plants growing in shade were constitutively more susceptible and did not induce resistance. In a more controlled field experiment, plant hormones were higher in the sun (jasmonic acid, salicylic acid, abscisic acid, indole acidic acid) and were induced by herbivory (jasmonic acid and abscisic acid). In particular, the jasmonate burst following herbivory was halved in plants raised in shaded habitats, and this correspondingly reduced latex induction (but not cardenolide induction). Thus, we provide a mechanistic basis for the attenuation of induced plant resistance in low resource environments. Additionally, there appears to be specificity in these interactions, with light-mediated impacts on jasmonate-induction being stronger for latex exudation than cardenolides.

Crescimento de mudas de pau-brasil (Caesalpinia echinata Lam.), submetidas a cinco níveis de sombreamento

O objetivo deste estudo foi avaliar o crescimento de mudas de pau-brasil (Caesalpinia echinata Lam.), submetidas a cinco níveis de sombreamento. As mudas, com 18 meses de idade, foram submetidas aos níveis de 0, 20, 40, 60 e 80% de sombreamento, sob estrutura de telados pretos, tipo sombrite. Os maiores valores para altura foram obtidos em plantas cultivadas sob 20, 40 e 60% de sombreamento. Plantas sob pleno sol e sob 20% de sombreamento apresentaram maiores diâmetros do colo e menores relações entre altura e diâmetro do colo, o que revela maior equilíbrio no crescimento. O maior número de folhas foi obtido em plantas sob pleno sol. O aumento da luminosidade ocasionou maiores massas de matéria seca da parte aérea, do sistema radicular e total, além de menores índices entre massa de matéria seca da parte aérea e das raízes, o que sugere maior investimento de biomassa para as raízes. Os maiores valores do Índice de Qualidade de Dickson (IQD) foram observados em mudas cultivadas sob menores índices de sombreamento, sendo um bom indicador da qualidade das mudas.

Boldo ( Peumus boldus) cultivated under different light conditions, soil humidity and plantation density

Boldo ( Peumus boldus Mol.) is a medicinal plant native to the central zone of Chile and part of the sclerophyll forest. More than 2000 tons of dried leaves exported annually are wild collected. To develop a cultivation system that supports sustainable production of boldo leaves, we have studied growth and harvest of boldo under different light and soil water conditions. The leaf yield per plant as well as the alkaloid and essential oil content were the same for plants grown under shade and for plants exposed to full sun. The only difference between the shaded and the full sun plants was a higher percentage of stem in the harvested product of shade grown plants. This result would permit the intercropping of boldo in forest plantations without affecting the leaf yield and medicinal quality. The excellent adaptation to dry conditions was confirmed, as the different treatments of soil water led to similar leaf yields and plant heights. Plants submitted to water stress produced fewer but longer shoots and contained less essential oil. None of the treatments except water stress affected the medicinal quality requirements of alkaloid or essential oil concentration in the leaves. Wild collected leaves are inexpensive because of low production costs. To be able to compete with wild supplied leaves in the international market, we have evaluated high density plantings as a way to lower costs of a cultivated product by mechanizing harvest. High planting densities led to loweryielding individuals, but leaf yield per area increased. Plant height and the percentage of leaves in the harvested product was the same for densities of 8- and 16 plants m −2. The leaves produced by cultivated boldo generally fulfill the requirements described in the European Pharmacopoeia. We conclude that boldo can be successfully cultivated under the described cultivation conditions.

Light Exposure and Shade Effects on Growth, Flowering, and Leaf Morphology of Spiraea alba Du Roi and Spiraea tomentosa L

Two native shrubs, Spiraea alba (meadowsweet) and Spiraea tomentosa (hardhack or steeplebush), have potential as landscape plants, but little is known about light requirements for these species. The performance of plants from four geographical seed sources of each species was evaluated in the field under six different light treatments: full sun; morning full sun; afternoon full sun; and 40%, 60%, and 80% shade. Provenance differences did exist for height, flowering, and leaf greenness. Growth, flowering, and canopy density were greater in full sun and 40% shade and least in 80% shade. Both species responded to shade with increased individual leaf area and higher specific leaf area. Relative leaf greenness decreased with shade in S. tomentosa but did not change in S. alba. Plants grown in morning or afternoon shade were shorter and smaller and had fewer inflorescences than did the full-sun plants. These species can survive in deep shade, but based on growth and appearance, they are best suited to full sun or light shade in the landscape.

Metabolismo de nitrogênio em dois sistemas de cultivo de café sob veranico da estação úmida

Com o objetivo de avaliar o efeito do veranico ocorrido na estação úmida sobre o metabolismo de nitrogênio em cafeeiros em sistema a pleno sol e associados com abacateiro (Persea americana Mill.) e ingazeiro (Inga edulis Mart.), foi realizado este experimento. O estudo foi conduzido em propriedade situada no município de Barra do Choça, BA, composto por plantas de café (Coffea arabica L.), variedade Catuaí, sendo caracterizados dois campos experimentais (sistema sombreado x sistema a pleno sol). As avaliações foram realizadas em janeiro (período de veranico) e março (final da estação úmida), em cinco repetições por campo experimental. Os dados foram submetidos ao teste t por meio do programa SAEG, versão 9.1. Maior teor de NO3 - foi verificado no sistema a pleno sol, tanto no período de veranico como no final da estação úmida. Em março foi observado maior acúmulo de N-orgânico no terço superior do cafeeiro a pleno sol e no terço médio do cafeeiro sombreado. Maiores teores de nitrogênio total e a tendência de maior atividade enzimática da redutase do nitrato foram verificados nos sistemas arborizados, quando avaliados dentro do mesmo terço do cafeeiro nas duas estações.

Corn Response to Competition: Growth Alteration vs. Yield Limiting Factors

Competition mechanisms among adjacent plants are not well understood. This study compared corn growth and yield responses to water, N, and shade at 74,500 plants ha−1 (1×) with responses to water and N when planted at 149,000 plant ha−1. Plant biomass, leaf area, chlorophyll content, reflectance, and enzyme expression (transcriptome analysis) were measured at V‐12. Grain and stover yields were measured with grain analyzed for 13C isotopic discrimination (Δ) and N concentration. At V‐12, 60% shade plants had increased chlorophyll and reduced leaf area and height compared to full sun plants. In the 2× treatment, plants had 11% less chlorophyll than 1× plants with leaf area and height similar to 60% shade plants. At harvest, plants in the 2× treatment were smaller, had increased water and N use efficiency, and an 11% per hectare yield increase compared with the 1× unstressed treatment. Per‐plant yields from 60% shade and 2× treatments were 50% less than 1× unstressed treatment. Yield reduction in shaded plants was attributed to light stress. Lower yield in the 2× treatment was attributed to a population‐density induced 20% decrease in the red/near‐infrared (NIR) ratio, which resulted in downregulation of C4 carbon metabolism enzymes (phosphoenolpyruvate carboxykinase, phosphoenolpyruvate carboxylase, and pyruvate orthophosphate dikinase). Although the net impact of high plant density and shade stress on per‐plant yield were similar, the stress compensation mechanisms differed.

Analysis of Kaolin Particle Film Use and Its Application on Coffee

Application of a kaolin-based particle film, Surround WP, was analyzed using glass plates and slides. The kaolin was sprayed on coffee grown in full sun to evaluate physiological responses to this shading technique. Kaolin reduced photosynthetically active radiation and ultraviolet transmission and decreased surface temperatures on glass slides. In the second year of application, photosynthesis of plants sprayed with kaolin was 71% greater than full-sun plants and yields were doubled. Leaf temperature was significantly lower in the kaolin treatment, but stable C isotope ratios, water use efficiency, nodal growth, and specific leaf area were not. The most likely mechanisms for increased yield are increased light transmittance to inner-canopy nodes or greater storage of photosynthate during the first year. Although results from this study suggest there is much promise for improving the performance and yield of coffee with kaolin application, studies with other species have shown inconsistent results. This inconsistency may be linked to variation in application techniques, kaolin coverage and subsequent effects on light transmission, leaf temperature, and physiological function. Thus, reports on physiological performance alone are insufficient to evaluate the use of kaolin application. Detailed information on application techniques combined with measurements of end-product criteria such as yield or quality are recommended to facilitate cross-study comparisons.