Correlating Coffea canephora 3D architecture to plant photosynthesis at a daily scale and vegetative biomass allocation.

Coffea canephora (C. canephora) has two botanical varieties, Robusta and Conilon. Intraspecific variability was hypothesized and projected for the selection of C. canephora plants able to maintain production in the context of global climate changes. For that, architectural, C-assimilation and biomass analyses were performed on 17-month-old Robusta (clones 'A1' and '3 V') and Conilon (clones '14' and '19') varieties grown in non-limiting soil, water and mineral nutrient conditions. Nondestructive coffee plant architecture coding, reconstruction and plant photosynthesis estimations were performed using a functional-structural plant modeling platform OpenAlea. 3D reconstructions and inclusion of parameters calculated and estimated from light response curves, such as dark respiration (Rd), maximum rate of carboxylation of RuBisCO and photosynthetic electron transport allowed the estimation of instantaneous and daily plant photosynthesis. The virtual orchard leaf area index was low, and light was not a limiting factor in early C. canephora development stages. Under such conditions, Robusta assimilated more CO2 at the plant and orchard scale and produced higher total biomass than Conilon. Lower plant daily photosynthesis and total biomass were correlated to higher Rd in Conilon than in Robusta. Among the architectural traits, leaf inclination, size and allometry were most highly correlated with plant assimilation and biomass. Relative allocation in leaf biomass was higher in '19' Conilon than in young Robusta plants, indicating intraspecific biomass partitioning. Similarly, variation in relative distribution of the root biomass and the root volume reflected clonal variation in soil occupation, indicating intraspecific variability in space occupation competitiveness. Coffea canephora denoted high root allocation in both Conilon and Robusta clones. However, relevant differences at subspecific levels were found, indicating the high potential of C. canephora to cope with drought events, which are expected to occur more frequently in the future, because of climate changes. The methodology developed here has the potential to be used for other crops and tree species. Highlights Functional-structural plant model was used to estimate photosynthesis on a plant and daily scales in Coffea canephora (C. canephora). Among the architectural traits, leaf shape and inclination had the most impact on photosynthesis and biomass. Under non-limiting conditions, Robusta had higher plant photosynthesis and biomass than Conilon. A higher leaf biomass allocation in Conilon clone '19' than in Robusta suggested variety-specific partitioning. Variation in the relative distribution of the root biomass indicated C. canephora intraspecific soil occupation variability.

Biomass and Leaf Acclimations to Ultraviolet Solar Radiation in Juvenile Plants of Coffea arabica and C. canephora.

Despite the negative impacts of increased ultraviolet radiation intensity on plants, these organisms continue to grow and produce under the increased environmental UV levels. We hypothesized that ambient UV intensity can generate acclimations in plant growth, leaf morphology, and photochemical functioning in modern genotypes of Coffea arabica and C. canephora. Coffee plants were cultivated for ca. six months in a mini greenhouse under either near ambient (UVam) or reduced (UVre) ultraviolet regimes. At the plant scale, C. canephora was substantially more impacted by UVam when compared to C. arabica, investing more carbon in all juvenile plant components than under UVre. When subjected to UVam, both species showed anatomic adjustments at the leaf scale, such as increases in stomatal density in C. canephora, at the abaxial and adaxial cuticles in both species, and abaxial epidermal thickening in C. arabica, although without apparent impact on the thickness of palisade and spongy parenchyma. Surprisingly, C. arabica showed more efficient energy dissipation mechanism under UVam than C. canephora. UVam promoted elevated protective carotenoid content and a greater use of energy through photochemistry in both species, as reflected in the photochemical quenching increases. This was associated with an altered chlorophyll a/b ratio (significantly only in C. arabica) that likely promoted a greater capability to light energy capture. Therefore, UV levels promoted different modifications between the two Coffea sp. regarding plant biomass production and leaf morphology, including a few photochemical differences between species, suggesting that modifications at plant and leaf scale acted as an acclimation response to actual UV intensity.

Linking root and stem hydraulic traits to leaf physiological parameters in Coffea canephora clones with contrasting drought tolerance.

Knowing the key hydraulic traits of different genotypes at early seedling stages can potentially provide crucial information and save time for breeding programs. In the current study we investigated: (1) how root, stem and whole plant conductivities are linked to xylem traits, and (2) how the integrated hydraulic system impacts leaf water potential, gas exchange, chlorophyll a fluorescence and the growth of three coffee cultivars (clones of Coffea canephora Pierre ex Froehner cv. Conilon) with known differences in drought tolerance. The Conilon clones CL 14, CL 5 V and CL 109A, classified as tolerant, moderately tolerant, and sensitive to drought respectively, were grown under non-limiting soil-water supply but high atmospheric demand (i.e., high VPDair). CL 14 and CL 5 V displayed higher root and stem hydraulic conductance and conductivity, and higher whole plant conductivity than CL 109A, and these differences were associated with higher root growth traits. In addition, CL 109A exhibited a non-significant trend towards wider vessels. Collectively, these responses likely contributed to reduce leaf water potential in CL 109A, and in turn, reduced leaf gas exchange, especially during elevated VPDair. Even when grown under well-watered conditions, the elevated VPDair observed during this study resulted in key differences in the hydraulic traits between the cultivars corresponding to differences in plant water status, gas exchange, and photochemical activity. Together these results suggest that coffee hydraulic traits, even when grown under non-water stress conditions, can be considered in breeding programs targeting more productive and efficient genotypes under drought and high atmospheric demand.

Physical and physiological quality of seeds of Campo Grande Stylosanthes coated with different binder materials / Qualidade física e fisiológica de sementes de Stylosanthes Campo Grande revestidas com diferentes materiais cimentantes

ABSTRACT: The binder materials used in seed coating provide adherence of the filler materials onto the seeds. Adequate concentrations of the binder promote good physical characteristics of coating while not impairing seed physiological characteristics. Thus, the objective of this study was to evaluate the type and the concentration of binder materials that allow the best physical and physiological characteristics in coated seeds of Campo Grande Stylosanthes. Seed coating was carried out in a coating pan, using sand as the filling material. The treatments consisted of 2 types of binders mixed in 3 ratios (PVA glue and gum arabic glue, diluted in water, 3:1, 2:1, and 1:1), and uncoated seeds as control. The coated seeds were evaluated for physical and physiological characteristics. The laboratory and greenhouse experiments were arranged in a completely randomized design. Results showed that at the different concentrations used this study, neither the PVA glue nor the gum arabic glue had any effect on the physiological quality of Campo Grande Stylosanthes seeds. However, PVA glue in the ratio of 2:1 provided the greatest surface area, maximum diameter, minimum diameter, and sphericity to coated seeds.

RESUMO: No processo de revestimento, os materiais cimentantes são os responsáveis por conferir a adesão dos materiais de enchimento às sementes. Concentrações adequadas de material cimentante promovem revestimento com boas características físicas e que não prejudiquem as características fisiológicas das sementes. Assim, o objetivo desse trabalho foi verificar o tipo e a concentração de material cimentante que possibilite as melhores características físicas e fisiológicas em sementes revestidas de estilosantes Campo Grande. O revestimento foi realizado em drageadora, utilizando areia como material de enchimento. Os tratamentos foram compostos por 2 tipos de materiais cimentantes em 3 proporções (cola cascorez extra e cola goma arábica, diluídas em água, 3:1, 2:1 e 1:1), além das sementes não revestidas, como controle. Após o revestimento, as sementes foram avaliadas quanto às características físicas e fisiológicas. O delineamento adotado foi inteiramente casualizado em laboratório e em casa de vegetação. Verificou-se que as colas cascorez extra e goma arábica não interferiram na qualidade fisiológica das sementes de estilosantes Campo Grande nas diferentes concentrações utilizadas. Entretanto, a cola cascorez extra na proporção 2:1 proporcionou maior área, diâmetro máximo, diâmetro mínimo e esfericidade nas sementes revestidas.