What Traits Should Be Measured for Biomass in Kenaf?

Kenaf (Hibiscus cannabinus L.) is widely used as an important industrial crop. It has the potential to act as a sustainable energy provider in the future, and contains beneficial compounds for medical and therapeutic use. However, there are no clear breeding strategies to increase its biomass or leaf volume. Thus, to attain an increase in these parameters, we examined potential key traits such as stem diameter, plant height, and number of nodes to determine the relationship among them. We hypothesized that it would be easier to reduce the amount of time and labor required for breeding if correlations among these parameters are identified. In this study, we found a strong positive correlation between height and number of nodes (Spearman’s Rho = 0.67, p < 0.001) and number of nodes and stem diameter (Spearman’s Rho = 0.65, p < 0.001), but a relatively low correlation (Spearman’s Rho = 0.34, p < 0.01) between height and stem diameter in the later stages of kenaf growth. We suggest that an efficient breeding strategy could be devised according to the breeding purpose, considering the correlations between various individual traits of kenaf.

Accelerating leaf area measurement using a volumetric approach

Despite the advances in the techniques of indirect estimation of leaf area, the destructive measurement approaches have still remained as the reference and the most accurate methods. However, even utilizing the modern sensors and applications usually requires the laborious and time-consuming practice of unfolding and analyzing the single leaves, separately. In the present study, a volumetric approach was tested to determine the pile leaf area based on the ratio of leaf volume divided by thickness. For this purpose, the suspension technique was used for volumetry, which is based on the simple practice and calculations of the Archimedes principle. The results indicated that the wheat volumetric leaf area (VLA), had an approximately 1:1 correlation with the conventionally measured optical leaf area (OLA). Exclusion of the midrib volume from calculations, did not affect the estimation error (i.e. NRMSE less than 2.61%); however, improved the slope of the linear model by about 6%. The error of sampling for determining the mean leaf thickness of the pile, was also less than 2% throughout the season. Besides, a more practical and facilitated version of the pile volumetry was tested using a Specific Gravity Bench (SGB), which is currently available as a laboratory equipment. As an important observation, which was also expectable according to the 3D shape of the leaf (i.e. expansion in a 2D plane), it was evidenced that the variations in the OLA exactly follows the pattern of the changes in the leaf volume. Accordingly, it was suggested that the relative leaf areas of various experimental treatments may be compared directly based on the volume, and independently of leaf thickness. Furthermore, no considerable difference was observed among the OLAs measured using various image resolutions (NRMSE < 0.212%); which indicates that even the current superfast scanners with low resolutions as 200 dpi may be used for a precision optical measurement of leaf area. It is expected that utilizing the reliable and simple concept of volumetric leaf area, based on which the measurement time may be independent of the sample size, facilitate the laborious practice of leaf area measurement; and consequently, improve the precision of the field experiments.

Maximum CO 2 diffusion inside leaves is limited by the scaling of cell size and genome size

Maintaining high rates of photosynthesis in leaves requires efficient movement of CO 2 from the atmosphere to the mesophyll cells inside the leaf where CO 2 is converted into sugar. CO 2 diffusion inside the leaf depends directly on the structure of the mesophyll cells and their surrounding airspace, which have been difficult to characterize because of their inherently three-dimensional organization. Yet faster CO 2 diffusion inside the leaf was probably critical in elevating rates of photosynthesis that occurred among angiosperm lineages. Here we characterize the three-dimensional surface area of the leaf mesophyll across vascular plants. We show that genome size determines the sizes and packing densities of cells in all leaf tissues and that smaller cells enable more mesophyll surface area to be packed into the leaf volume, facilitating higher CO 2 diffusion. Measurements and modelling revealed that the spongy mesophyll layer better facilitates gaseous phase diffusion while the palisade mesophyll layer better facilitates liquid-phase diffusion. Our results demonstrate that genome downsizing among the angiosperms was critical to restructuring the entire pathway of CO 2 diffusion into and through the leaf, maintaining high rates of CO 2 supply to the leaf mesophyll despite declining atmospheric CO 2 levels during the Cretaceous.

Impact of colchicine on leaf morphology and stomatics of Kalanchoe tubiflora (Harv.) Raym.-Hamet (Crassulaceae)

The demand of medicinal plants for consumption is greatly increasing worldwide. The conventional breeding programs are generally dependent on the environment prone to biotic and abiotic stresses. These added to the low content of secondary metabolites at harvest, bring the need for artificial development of polyploid individuals as an alternative to increase productivity. Consequently, the present study evaluated the effect of different colchicine concentrations and exposure time, on Kalanchoe tubiflora leaf morphology and stomata. Initially, K. tubiflora seedlings were harvested and submitted to colchicine concentrations of 0, 0.025, 0.05 and 0.1 % and at two exposure times (24 and 48 hours). Subsequently, morphological measurements such as plant height, leaf width, leaves number, leaf length, leaf thickness and leaf volume every 15 days were made for 16 weeks after planting. Then, the stomata were characterized, taking into account the width, length, stomatal index and the number of chloroplasts per stoma. A significant increase in leaf morphology was found in colchicine treatments of 0.025 % at 48 h and 0.1 % at 24 h. A significant increase in stomatal morphology with the treatment of 0.025 % at 24 h was also recorded. This shows that the correct application of colchicine in term of quantity and time could produce greater growth in a short period and increase the biomass of K. tubiflora medicinal plant.

Differential shrinkage of mesophyll cells in transpiring cotton leaves: implications for static and dynamic pools of water, and for water transport pathways

Shrinkage of palisade cells during transpiration, previously measured for sclerophyllous leaves of Eucalyptus where cells shrank equally, was compared with shrinkage in thin mesophytic leaves of cotton (Gossypium hirsutum L.). Selected vapour pressure differences (Δe) from 0.6 to 2.7 kPa were imposed during steady-state photosynthesis and transpiration. Leaves were then cryo-fixed and cryo-planed paradermally, and images obtained with a cryo-scanning electron microscope (CSEM). Diameters of palisade ‘cavity cells’ within sub-stomatal cavities, and surrounding palisade ‘matrix cells’ were measured on CSEM images. Cavity and spongy mesophyll cells shrank progressively down to Δe = 2.7 kPa, while matrix cells remained at the same diameter at all Δe. Diameters were also measured of cavity and matrix cells quasi-equilibrated with relative humidities (RHs) from 100% to 86%. In leaves quasi-equilibrated with 95% RH, the cavity cells shrank so much as to be almost unmeasurable, while matrix cells shrank by only 6%. These data suggest that there are two distinct pools of water in cotton leaves: cavity plus spongy mesophyll cells (two-thirds of leaf volume) which easily lose water; and matrix cells (one-third of leaf volume), which retain turgor down to relative water loss = 0.4, providing structural rigidity to prevent wilting. This phenomenon is probably widespread among mesophytic leaves.

Seasonal dynamics of three inquiline species in isolated island populations of Sarracenia purpurea L. in Lake Michigan

A seasonal survey of the abundances of three inquilines species in Sarracenia purpurea L. leaves was conducted by sampling 240 leaves from three pitcher plant populations on Beaver Island in Lake Michigan, United States. Leaf characteristics such as fluid pH, fluid volume, and keel length were quantified. The study focused primarily on the larvae of three dipteran inquiline species – the midge, Metriocnemus knabi Coquillet, the mosquito, Wyeomyia smithii (Coquillet), and the flesh fly, Fletcherimyia fletcheri Aldrich. Dipteran inquiline abundances varied with sampling season. Most pitchers contained one of the three studied inquilines species. Mosquito abundances were low relative to the other inquilines. In samples collected soon after new leaves open, a mixture of mosquito and midge larvae was characteristic. We related inquilines abundances to leaf parameters using generalized linear mixed models. The midge and mosquito responded differently to leaf parameters during different sampling seasons, where as the flesh fly showed no response. The most important leaf parameters were pH and percent of total leaf volume filled with fluid (relative volume). The midge and mosquito were more likely to be present in pitchers with low pH and higher fluid volume. Our results indicate that pitchers of isolated northern populations of S. purpurea are inhabited by a less diverse insect community than reported elsewhere. Our study also suggests that site isolation may play an important role in the seasonal variation of inquiline community structure.

AVALIAÇÃO DOS TEORES NUTRICIONAIS EM LARANJEIRA ‘VALÊNCIA’, SOB FERTIRRIGAÇÃO

AVALIAÇÃO DOS TEORES NUTRICIONAIS EM LARANJEIRA ‘VALÊNCIA’, SOB FERTIRRIGAÇÃO Carlos Renato Alves Ragozo1; Leonardo Theodoro Büll2; Roberto Lyra Villas Bôas2; Luiza Helena Duenhas31JR Ragozo Ltda., São Manuel, SP, [email protected] de Recursos Naturais, Faculdade de Ciências Agronômicas, Universidade Estadual Paulista, Botucatu, SP3Centro de Pesquisa Agropecuária do Trópico Semi-Árido, EMBRAPA, Petrolina, PE 1 RESUMO O objetivo deste trabalho foi comparar fertirrigação e adubação convencional em um pomar de laranja ‘Valência’ com cinco anos de idade, irrigado por microaspersão. As adubações convencionais, utilizando a dosagem recomendada para a cultura, foram parceladas em três vezes durante o ano. Nos tratamentos de fertirrigação, utilizou-se a dose inteira, ½ e ⅓ da adubação convencional, parceladas em dez vezes ao ano. Avaliou-se a circunferência do tronco e volume de copa, o teor de clorofila nas folhas, a produção e qualidade dos frutos. Para o primeiro ano de experimentação não ocorreram diferenças significativas entre os tratamentos para as características avaliadas, porém observou-se que os tratamentos fertirrigados ocasionaram menores desequilíbrios nutricionais, determinados pelo DRIS. O tratamento de fertirrigação com ½ da dose da adubação convencional mostrou o melhor desempenho com relação à produção e qualidade da fruta. UNITERMOS: Citrus sinensis, fertirrigação, DRIS. RAGOZO, C. R. A.; BÜLL, L. T.; BÔAS, R. L. V.; DUENHAS, L. H. EVALUATION OF MINERAL NUTRIENT CONTENTS IN PLANTS OF ‘VALÊNCIA’ ORANGE SUBMITTED TO FERTIGATION 2 ABSTRACT This work aimed to compare fertigation to conventional fertilization in a five- year-old ‘Valência’ orange orchard, irrigated by microsprinklers. The conventional fertilization, using the recommended dosage for the crop, was parceled out in three during the year. In the fertigation treatments a complete dose, ½ and ⅓ of the conventional fertilization dose, parceled out in ten in a year, were used. Trunk circumference and leaf volume, leaf chlorophyll content and fruit yield and quality were measured. For the first year, significant differences among the treatments for the evaluated parameters were not observed; however, it was noticed that fertigation treatments caused less nutritional unbalance, obtained by DRIS. The fertigation treatment using half dosage showed the best result regarding to fruit yield and quality. KEY WORDS: Citrus sinensis range, fertigation, DRIS

Photosynthesis and Growth Responses to Irradiance in Soybean (Glycine max) and Three Broadleaf Weeds

Photosynthesis and growth responses to irradiance level during growth were compared in soybean (Glycine maxL. Merr. ‘Century’) and three broadleaf weeds to determine if these responses were associated with differences in shade tolerance among species. In response to reduced irradiance during growth, leaf thickness of all species decreased, while chlorophyll content per unit leaf volume and photosynthetic rate per unit leaf volume, measured at low irradiance, increased. Soybean and common cocklebur (Xanthium strumariumL. #3XANST) also exhibited a decrease in soluble proteins on a leaf volume basis under reduced irradiance, and common cocklebur further exhibited a decrease in ribulose-1,5-bisphosphate carboxylase (RuBPcase) protein per unit leaf volume. Decreased irradiance during growth did not alter the content of RuBPcase or other soluble proteins per unit leaf volume in jimsonweed (Datura stramoniumL. # DATST) or velvetleaf (Abutilon theophrastiMedic. # ABUTH). The superior shade tolerance of common cocklebur compared to the other species was attributed in part to the levels of RuBPcase and other photosynthetic proteins in leaves developed at low irradiance.

Effects of Shade on Gas Exchange and Growth in Seedlings of Eucalyptus grandis Hill ex Maiden

E. grandis seedlings grown under conditions of high (12.6) and low (2.8 Em-2 day-) daily integrals of photon flux density exhibited the same light response of photosynthesis when the rates were expressed on a unit leaf volume basis. The conversion of photosynthetic substrate to dry matter was more efficient in larger than in smaller plants. Allocation of dry matter between leaves, stem and roots was influenced relatively little by the shading treatments, but the utilization of dry matter by the leaves and stem was affected. Plants raised under low light exhibited significantly greater areas per unit weight of leaf, and significantly greater lengths per unit weight of stem than did plants raised in the high-light treatment. Adaptation to shading in E. grandis seedlings was judged to be limited. A model was constructed which described adequately the growth of these seedlings after the age of about 14 days.

The leaf anatomy of beech, Fagus grandifolia

Observations have been made on the anatomy of beech, Fagus grandifolia Ehrh., with an emphasis on quantitative features. All surface areas and volumes were determined by projecting 2-μm serial sections, measuring them with a map tracer, and multiplying cell perimeters by section thickness or by the trace–cut–weight method. The organization of tissues, including a complex reticulate venation, is typical of many dicotyledons. Of the minor veins, only the quinternaries and veinlets lack bundle sheath extensions and have wholly parenchymatous bundle sheaths, the cells of which are often oriented at right angles to the vein. There are 12.1 mm of vein per square millimetre of leaf surface area, and 10 μm of vein (the diameter of a mesophyll cell) serves about 21.5 mesophyll cells. The mean maximum distance over which water and solutes must move between vascular tissue and mesophyll is 55 μm. The mesophyll cell walls may provide the pathway through which the bulk of the water moves; the volume occupied by the mesophyll cell walls is 55.7 mm3 or 11% of total leaf volume. The evaporative surface of the mesophyll is 13.36 mm2/mm2 leaf surface area.