Decoding the effects of drought stress on popcorn (Zea mays var. everta) flowering combining proteomics and physiological analysis

Under conditions of soil water limitation and adequate irrigation, we conducted an investigation into the growth dynamics, gas exchange performance, and proteomic profiles of two inbred popcorn lines-L71, characterized as drought-tolerant, and L61, identified as drought-sensitive. Our goal was to uncover the mechanisms associated with tolerance to soil water limitation during the flowering. The plants were cultivated until grain filling in a substrate composed of perlite and peat within 150cm long lysimeter, subjected to two water conditions (WC): i) irrigated (WW) at lysimeter capacity (LC - 100%), and ii) water-stressed (WS). Under WS conditions, the plants gradually reached 45% of LC and were maintained at this level for 10 days. Irrespective of the WC, L71 exhibited the highest values of dry biomass in both shoot and root systems, signifying its status as the most robust genotype. The imposed water limitation led to early senescence, chlorophyll degradation, and increased anthocyanin levels, with a more pronounced impact observed in L61. Traits related to gas exchange manifested differences between the lines only under WS conditions. A total of 1838 proteins were identified, with 169 differentially accumulated proteins (DAPs) in the tolerant line and 386 DAPs in the sensitive line. Notably, differences in energy metabolism, photosynthesis, oxidative stress response, and protein synthesis pathways were identified as the key distinctions between L71 and L61. Consequently, our findings offer valuable insights into the alterations in proteomic profiles associated with the adaptation to soil water limitation in popcorn.

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.

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 VPD_air). 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 VPD_air. Even when grown under well-watered conditions, the elevated VPD_air 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.