Total Leaf Dry Mass Research Articles

Forage Mass Estimation in Silvopastoral and Full Sun Systems: Evaluation through Proximal Remote Sensing Applied to the SAFER Model

The operational slowness in the execution of direct methods for estimating forage mass, an important variable for defining the animal stocking rate, gave rise to the need for methods with faster responses and greater territorial coverage. In this context, the aim of this study was to evaluate a method to estimate the mass of Urochloa brizantha cv. BRS Piatã in shaded and full sun systems, through proximal sensing applied to the Simple Algorithm for Evapotranspiration Retrieving (SAFER) model, applied with the Monteith Radiation Use Efficiency (RUE) model. The study was carried out in the experimental area of Fazenda Canchim, a research center of Embrapa Pecuária Sudeste, São Carlos, SP, Brazil (21°57′S, 47°50′W, 860 m), with collections of forage mass and reflectance in the silvopastoral systems animal production and full sun. Reflectance data, as well as meteorological data obtained by a weather station installed in the study area, were used as input for the SAFER model and, later, for the radiation use efficiency model to calculate the fresh mass of forage. The forage collected in the field was sent to the laboratory, separated, weighed and dried, generating the variables of pasture total dry mass), total leaf dry mass, leaf and stalk dry mass and leaf area index. With the variables of pasture, in situ, and fresh mass, obtained from SAFER, the training regression model, in which 80% were used for training and 20% for testing the models. The SAFER was able to promisingly express the behavior of forage variables, with a significant correlation with all of them. The variables that obtained the best estimation performance model were the dry mass of leaves and stems and the dry mass of leaves in silvopastoral and full sun systems, respectively. It was concluded that the association of the SAFER model with the proximal sensor allowed us to obtain a fast, precise and accurate forage estimation method.

Plant growth and phytoactive alkaloid synthesis in kratom [Mitragyna speciosa (Korth.)] in response to varying radiance.

Leaves harvested from kratom [Mitragyna speciosa (Korth.)] have a history of use as a traditional ethnobotanical medicine to combat fatigue and improve work productivity in Southeast Asia. In recent years, increased interest in the application and use of kratom has emerged globally, including North America, for its potential application as an alternative source of medicine for pain management and opioid withdrawal syndrome mitigation. Although the chemistry and pharmacology of major kratom alkaloids, mitragynine and 7-hydroxymitragynine, are well documented, foundational information on the impact of plant production environment on growth and kratom alkaloids synthesis is unavailable. To directly address this need, kratom plant growth, leaf chlorophyll content, and alkaloid concentration were evaluated under three lighting conditions: field full sun (FLD-Sun), greenhouse unshaded (GH-Unshaded), and greenhouse shaded (GH-Shaded). Nine kratom alkaloids were quantified using an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Greenhouse cultivation generally promoted kratom height and width extension by 93–114% and 53–57%, respectively, compared to FLD-Sun. Similarly, total leaf area and leaf number were increased by 118–160% and 54–80% under such conditions. Average leaf size of plants grown under GH-Shaded was 41 and 69% greater than GH-Unshaded and FLD-Sun, respectively; however, no differences were observed between GH-Unshaded and FLD-Sun treatments. At the termination of the study, total leaf chlorophyll a+b content of FLD-Sun was 17–23% less than those grown in the greenhouse. Total leaf dry mass was maximized when cultivated in the greenhouse and was 89–91% greater than in the field. Leaf content of four alkaloids to include speciociliatine, mitraphylline, corynantheidine, and isocorynantheidine were not significantly impacted by lighting conditions, whereas 7-hydroxymitragynine was below the lower limit of quantification across all treatments. However, mitragynine, paynantheine, and corynoxine concentration per leaf dry mass were increased by 40%, 35%, and 111%, respectively, when cultivated under GH-Shaded compared to FLD-Sun. Additionally, total alkaloid yield per plant was maximized and nearly tripled for several alkaloids when plants were cultivated under such conditions. Furthermore, rapid, non-destructive chlorophyll evaluation correlated well (r2 = 0.68) with extracted chlorophyll concentrations. Given these findings, production efforts where low-light conditions can be implemented are likely to maximize plant biomass and total leaf alkaloid production.

Trade-offs between growth, reproduction and defense in response to resource availability manipulations.

The Brazilian Cerrado is one of the most endangered biomes in the world. We evaluated the sustainability of leaf harvest in one of the most important Cerrado tree species, Stryphnodendron adstringens. The bark of this tree is used as a source of medicinal tannin. Harvesting bark, however, often kills the tree. In a manipulative field experiment, we tested the hypothesis that harvesting leaves, which might serve as an alternative source of tannin, would be less detrimental for tree survival, growth, reproduction, and defense than harvesting bark. In a two-way crossed experimental design, we either clipped 100% of a plant’s leaves or applied NPK fertilizer to the soil. Our predictions of the experimental outcomes were based on plant resource and defense theory. Growth was determined by total leaf dry mass production, reproduction by inflorescence and fruit production traits, and defense by total phenolics, hydrolyzable tannins, and condensed tannins. Fertilization had a marginally positive effect on total leaf dry mass. Defoliation had no effect on subsequent leaf production, and most importantly, no plants died as a result of defoliation. We found high tannin amounts in leaves of S. adstringens produced both prior to and subsequent to clipping, further suggesting that leaves could serve as a sustainable alternative source of tannin. After clipping, plants invested more in tannin production and less in reproduction. Our results suggest that leaf harvest may be more sustainable than harvesting of bark in S. adstringens. We suggest the need for further investigation of the medicinal properties of leaf tannins to formulate a viable sustainable management plan for the exploitation of this plant species.

<b>Manihot leaf abscission induced by ethrel

This study aimed to assess the impact of ethrel spraying on cassava leaf abscission at different stages of cultivar development. Two experiments were performed using randomized block designs, with 15 total treatments (three repetitions of five conditions) arranged according to the factorial scheme 3 x 5. Experiment 1 (ethrel application in the vegetative development period) consisted of three seasons (November 2013 and 2014, January and February 2014) and four concentrations of ethrel (1,500, 3,000, 4,500, and 6,000 ppm) and a control (no application); Experiment 2 (application in pre-harvest period) consisted of three periods of ethrel spraying (20, 40, and 60 days before harvest), four ethrel concentrations (1,500, 3,000, 4,500, and 6,000 ppm) and a control (without ethrel). The characteristics evaluated included the number of fallen leaves at 20 and 70 days after application, total leaf dry mass and foliar degreening. The effects of different concentrations and times of application of ethrel were significant during the first seven days. Ethrel application during the second period of vegetative development did not affect the number of fallen leaves over a period of 70 days.

Modeling Allometric Relationships in Leaves of Young Rapeseed (Brassica napus L.) Grown at Different Temperature Treatments.

Functional–structural plant modeling (FSPM) is a fast and dynamic method to predict plant growth under varying environmental conditions. Temperature is a primary factor affecting the rate of plant development. In the present study, we used three different temperature treatments (10/14°C, 18/22°C, and 26/30°C) to test the effect of temperature on growth and development of rapeseed (Brassica napus L.) seedlings. Plants were sampled at regular intervals (every 3 days) to obtain growth data during the length of the experiment (1 month in total). Total leaf dry mass, leaf area, leaf mass per area (LMA), width-length ratio, and the ratio of petiole length to leaf blade length (PBR), were determined and statistically analyzed, and contributed to a morphometric database. LMA under high temperature was significantly smaller than LMA under medium and low temperature, while leaves at high temperature were significantly broader. An FSPM of rapeseed seedlings featuring a growth function used for leaf extension and biomass accumulation was implemented by combining measurement with literature data. The model delivered new insights into growth and development dynamics of winter oilseed rape seedlings. The present version of the model mainly focuses on the growth of plant leaves. However, future extensions of the model could be used in practice to better predict plant growth in spring and potential cold damage of the crop.

Estimating aboveground biomass and leaf area of low-stature Arctic shrubs with terrestrial LiDAR

Arctic tundra ecosystems are responding to effects of climatic warming via shifts in vegetation composition and increased woody biomass. In this sensitive ecosystem, minor increases in woody plant biomass may induce significant changes in ecosystem structure and function. However, establishing methods for quantifying and potentially scaling woody plant biomass in low-stature biomes is challenging. In this study, we investigated the potential to use terrestrial laser scanning (TLS) to remotely estimate harvested biomass and leaf area of two dominant low-stature (<1.5m tall) Arctic shrub species in 0.64m2 subplots established in northern Alaskan tundra. We explored two biomass estimation approaches (volumetric surface differencing and voxel counting) applied to point clouds obtained from close-range (2m) and variable-range (<50m) terrestrial laser scans. Relationships between harvested biomass and TLS metrics were strong for all combinations of approaches, with voxel counting giving a marginally better result than surface differencing for close-range data (R2=0.94 vs 0.92; RMSE=102g vs 117g) and surface differencing proving stronger than voxel counting for variable-range data (R2=0.91 vs 0.82; RMSE=119g vs 169g). Strong relationships between total harvested biomass and total leaf dry mass (R2=0.93; RMSE=13.4g), and between leaf dry mass and leaf wet area (R2=0.99; RMSE=9.01cm2) justify estimation of shrub leaf area from TLS-derived shrub biomass. Our results show that rapidly acquired, repeatable terrestrial laser scans taken at multiple ranges can be processed using simple biomass estimation approaches to yield aboveground biomass and leaf area estimates for low-stature shrubs at fine spatial scales (sub-meter to ~50 meters) with the fidelity required to monitor small but ecologically meaningful changes in tundra structure. Further, these data may be employed as ground reference data for broader scale remote sensing data collection, such as airborne LiDAR scanning, that would enable shrub biomass and leaf-area estimates at fine spatial resolution over large spatial extents.

Acclimation to irradiance of leaf photosynthesis and associated nitrogen reallocation in photosynthetic apparatus in the year following thinning of a young stand of Chamaecyparis obtusa

In order to quantify the effects of thinning on photosynthetic parameters and associated change in leaf nitrogen (N) contents, half of the trees in a 10-year-old Chamaecyparis obtusa (Sieb. et Zucc.) Endl. stand (36° 3'N, 140°7'E) were removed, giving a final density of 1 500 trees ha-1, in May 2004. Photosynthetic photon flux density (PPFD) and leaf N and carbon (C) contents in the lower (L), middle (M), and upper (U) crowns were monitored one, three, and five months after thinning in both the thinned stand and a non-thinned control stand. In addition, leaves' photosynthetic responses to CO2 concentration were simultaneously measured in situ to estimate the maximum rates of carboxylation (Vcmax) and electron transport (Jmax). Thinning increased PPFD in the L and M crowns but not in the U crown. Vcmax in both the L and M crowns of the thinned stand increased significantly in comparison with the same crown position of the control stand in the three and five months following thinning. In addition, the thinned stand exhibited an increase in N partitioned to ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in the L and M crowns relative to the control stand three and five months after thinning, indicating that N had been redistributed within the photosynthetic machinery. Thinning did not affect N per unit area at any of the crown positions, but significantly increased the content of N as a fraction of the total leaf dry mass in the L and M crowns three and five months after thinning. This was a consequence of a decrease in leaf dry mass due to rapid shoot growth. Thus thinning did not cause a redistribution of N between leaves. Thinning improved irradiance in the L and M crowns of C. obtusa, leading to photosynthetic acclimation. Photosynthetic acclimation in the first year mainly occurred via redistribution of N within but not between leaves.

Frequency and Timing of Leaf Removal Affect Growth and Podophyllotoxin Content ofPodophyllum peltatumin Full Sun

Podophyllotoxin is a pharmaceutical compound found in leaves and rhizomes of American mayapple (P. peltatum L.), a species being investigated as an alternative to that of the Indian mayapple (P. emodi). Leaves alone can serve as a renewable source of podophyllotoxin (and other lignans) leaving rhizomes undisturbed to produce leaf biomass in subsequent years. It is not known, however, how frequently or severely plants can be defoliated without adversely affecting future plant growth, lignan content, or podophyllotoxin yield (g.m(-2)). This study compared harvest strategies that were mild to severe in frequency and timing of leaf removal. A wild population in full sun was subjected to leaf removal treatments of varying frequency (every year, every 2nd or 3rd year) and timing (early or late). Control plots not previously harvested were included every year. Plots were 1.0 m2 and established during spring of 2001. Duration of the study was four years. P. peltatum plants did not tolerate the most severe harvest treatment: annual harvest frequency in combination with early harvest time. Early annual harvests reduced total leaf dry mass and total leaf area in a consistent and linear manner. In contrast, plants tolerated annual harvests when conducted late in the growing season and tolerated early harvests when conducted every 2nd or 3rd year. The number of sexual shoots was reduced to zero by early annual harvests. Podophyllotoxin content was 2.7 to 6.5 times greater in leaves harvested early compared to those harvested late, though content was significantly greater in only two out of four years. In conclusion, we can recommend leaf removal every year from well-established P. peltatum populations grown in full sun if harvests are conducted late in the growing season. This harvest strategy ensures maximum podophyllotoxin yield without jeopardizing future leaf biomass yield. Leaves harvested early appear to have greater podophyllotoxin content, but we discourage early harvest every year. Instead, our results indicate that leaves can be harvested early every other year without reducing long-term performance of P. peltatum populations.

Frequency and Timing of Leaf Removal Affect Growth and Podophyllotoxin Content of American Mayapple in Shade

Leaves of American mayapple (Podophyllum peltatum) are being investigated as an alternative and renewable source of podophyllotoxin, a pharmaceutical compound used in the manufacture of several drugs. This study examined long-term performance of mayapple populations subjected to different harvest strategies. A naturally occurring population in shade was subjected to leaf removal treatments of frequency (every year, every 2nd or 3rd year) or timing (early or late season). Plots were 1.0 m2, established during Spring 2001, and treatments were applied from 2001 to 2004. Control plots not previously harvested were also included each year. Plants did not tolerate the severest of leaf removal treatments: early harvest time in combination with annual harvest frequency. Early annual harvests reduced total leaf dry mass and total leaf area in a quadratic manner. Late harvest conducted annually, and early harvest conducted every other year, also reduced leaf dry mass and area but not as much as early annual harvest. Plants harvested every year, early, or early every year produced fewer sexual shoots than other treatment combinations. Contents of α-peltatin, β-peltatin, and total lignans were higher for leaves harvested early than those harvested late during each year of the study, demonstrating that lignan contents were affected by leaf age and not treatment. In conclusion, our results for plants grown in shade show that leaves can be removed late in the growing season every 2nd or 3rd year or early every 3rd year without reducing long-term performance of the population. This is more restrictive than that reported for populations in full sun where plants tolerated late harvests every year.

Sennoside Yields in Tinnevelly Senna Affected by Deflowering and Leaf Maturity

Manual deflowering and leaf maturity were evaluated for effect on the yields of the bioactive sennosides A and B in Tinnevelly senna (Cassia angustifolia Vahl). Deflowering increased sennoside A and B concentration (percent dry weight) in leaves by 25%, the total leaf dry mass by 63%, and the harvest index by 22%, with the result that the sennoside A and B yield (grams) per plant doubled in response to deflowering. During the same time, net photosynthesis remained consistently lower in the deflowered plants. Youngest leaves had the greatest sennoside A and B concentration. A clone raised from cuttings of one seedling had lower sennoside A:B ratio than the plants raised from the seedlings. Although crop type and possibly environmental conditions influenced the sennoside A:B ratio, deflowering and leaf maturity had no effect. The sennoside A and B concentrations in the dried leaves of deflowered plants harvested in 1.5-hour intervals appeared to increase during the course of the day. Deflowering, harvesting of young leaves, and harvesting time of day constitute promising component technologies for field investigations.

Comparison of photosynthetic acclimation to elevated CO2 and limited nitrogen supply in soybean

Plants grown at elevated CO2 often acclimate such that their photosynthetic capacities are reduced relative to ambient CO2‐grown plants. Reductions in synthesis of photosynthetic enzymes could result either from reduced photosynthetic gene expression or from reduced availability of nitrogen‐containing substrates for enzyme synthesis. Increased carbohydrate concentrations resulting from increased photosynthetic carbon fixation at elevated CO2 concentrations have been suggested to reduce the expression of photosynthetic genes. However, recent studies have also suggested that nitrogen uptake may be depressed by elevated CO2, or at least that it is not increased enough to keep pace with increased carbohydrate production. This response could induce a nitrogen limitation in elevated‐CO2 plants that might account for the reduction in photosynthetic enzyme synthesis. If CO2 acclimation were a response to limited nitrogen uptake, the effects of elevated CO2 and limiting nitrogen supply on photosynthesis and nitrogen allocation should be similar. To test this hypothesis we grew non‐nodulating soybeans at two levels each of nitrogen and CO2 concentration and measured leaf nitrogen contents, photosynthetic capacities and Rubisco contents. Both low nitrogen and elevated CO2 reduced nitrogen as a percentage of total leaf dry mass but only low nitrogen supply produced significant decreases in nitrogen as a percentage of leaf structural dry mass. The primary effect of elevated CO2 was to increase non‐structural carbohydrate storage rather than to decrease nitrogen content. Both low nitrogen supply and elevated CO2 also decreased carboxylation capacity (Vcmax) and Rubisco content per unit leaf area. However, when Vcmax and Rubisco content were expressed per unit nitrogen, low nitrogen supply generally caused them to increase whereas elevated CO2 generally caused them to decrease. Finally, elevated CO2 significantly increased the ratio of RuBP regeneration capacity to Vcmax whereas neither nitrogen supply nor plant age had a significant effect on this parameter. We conclude that reductions in photosynthetic enzyme synthesis in elevated CO2 appear not to result from limited nitrogen supply but instead may result from feedback inhibition by increased carbohydrate contents.

Browse production and leaf phenology of some trees and shrubs in differentColophospermum mopanesavanna communities

Abstract Leaf dry mass (DM) at peak biomass was estimated for different plant communities in a semi‐arid savanna. These estimates included the total leaf DM, as well as estimates of the leaf DM at browsing heights of 1.5 m, 2.0 m and 5.0 m. The total leaf DM in the different plant communities ranged between 1 224 kg ha−1 and 2 672 kg ha−1. The contribution of individual woody species to the total leaf DM ha−1 is presented for each plant community. Colophospermum mopane contributed substantially to the total leaf DM in all communities. Monthly assessments were made of the abundance of leaves in different phonological states for the most important woody species in each plant community. Differences in the leaf carriage patterns and phenological composition of leaves between different plant communities, as well as between the most important woody species, were established. The long leaf‐carriage period of C. mopane, relative to the other represented tree species, underlies its potential importance as a fodder...