Lower Transpiration Rates Research Articles

Effects of organic mulching and regulated deficit irrigation on crop water status, soil and yield features in an orange orchard under Mediterranean climate

The adoption of soil and water conservation measures (SWCM) is essential for improving the use of natural resources and making the agro-systems more resilient to climate change. In this context, a three-years trial was carried-out in an orange orchard characterized by different soil management (SM, i.e., bare and organic mulched soils) and water regimes (WR, i.e., full irrigation, FI, and regulated deficit irrigation, RDI). In response to the applied SWCM, crop water status (CWS), soil and yield main features were explored using multiple soil-plant-atmosphere continuum (SPAC) monitoring approaches.Overall average water saving of 24 % was achieved under RDI in comparison to FI. The stem water potential revealed a year-dependent behaviour in accordance to the patterns of the main ancillary physiological indicators. The adoption of additional plant-based measurements provided continuous information on the CWS, both in terms of trunk water potential (TWP) and sap flow fluxes, resulting in higher absolute values of TWP (−0.93 ± 0.01 MPa versus −0.83 ± 0.00 MPa) and lower transpiration rates (0.64 ± 0.00 mm d−1 versus 0.88 ± 0.01 mm d−1) in mulched compared to bare soils. The soil water content showed higher rates under mulched soils than in bare soil condition, both in FI (up to 15 %) and RDI (up to 27 %) at 0.75 m from the tree trunk to the inter-row. Soil temperature was lower in mulched soils under RDI. However, a great time-variability was observed for most of the soil physical-chemical variables under study. Nevertheless, the application of SWCM improved the yield over the years, resulting in higher fruit weights under mulched FI conditions.Finally, the study suggests that the adoption of SWCM can serve as an efficient strategy to enhance soil and yield features, highlighting the critical role of using SPAC methodological tools for monitoring the CWS at the field level.

Characterization of Citrus Rootstock Under Conditions of Boron Toxicity

Boron (B) is an essential element for an adequate development of citrus orchards. However, citrus trees are vulnerable to high B concentrations, generating morphological and physiological alterations incompatible with the proper production of citrus. In this sense, citrus rootstocks can provide valuable capabilities to citrus trees including tolerance to different stresses. The objective of this work is the characterization of 2247 × 6070–02–2 citrus rootstock using as a reference Carrizo citrange rootstock under B toxicity conditions (2.5 mM boric acid). Carrizo citrange is a diploid hybrid, and 2247 × 6070–02–2 is a novel low-HLB-sensitive tetraploid. B excess effects were analyzed after four weeks of treatment using 0.05 (control) and 2.5 mM (toxicity) H3BO3 concentrations, respectively, in hydroponic growth conditions. The characterization of 2247 × 6070–02–2 rootstock compared to Carrizo citrange was performed by measuring physiological parameters in leaves related to photosynthesis, stress oxidative responses, B content, and gene expression. The lower transpiration rate and, especially, the higher expression of the CsXIP1;1 gene and the better antioxidant defense mechanisms shown by 2247 × 6070–02–2 make this rootstock more tolerant to high B content than Carrizo citrange.

Droughts Amplify Soil Moisture Losses in Burned Forests of Southeastern Amazonia

AbstractSoil moisture is a crucial variable mediating soil‐vegetation‐atmosphere water exchange. As climate and land use change, the increased frequency and intensity of extreme weather events and disturbances will likely alter feedbacks between ecosystem functions and soil moisture. In this study, we evaluated how extreme drought (2015/2016) and postfire vegetation regrowth affected the seasonality of soil water content (0–8 m depth) in a transitional forest in southeastern Amazonia. The experiment included three treatment plots: an unburned Control, an area burned every three years (B3yr), and an area burned annually (B1yr) between 2004 and 2010. We hypothesized that (a) soil moisture at B1yr and B3yr would be higher than the Control in the first years postfire due to lower transpiration rates, but differences between burned plots would decrease as postfire vegetation regrew; (b) during drought years, the soil water deficit in the dry season would be significantly greater in all plots as plants responded to greater evaporative demand; and (c) postfire recovery in the burned plots would cause an increase in evapotranspiration over time, especially in the topsoil. Contrary to the first expectation, the burned plots had lower volumetric water content than the Control plot. However, we found that droughts significantly reduced soil moisture in all plots compared to non‐drought years (15.6%), and this effect was amplified in the burned plots (19%). Our results indicate that, while compounding disturbances such as wildfires and extreme droughts alter forest dynamics, deep soil moisture is an essential water source for vegetation recovery.

Adaptation of stomatal conductance, photosynthesis and water-use efficiency at shoot and canopy scales in adjacent stands of Dacrycarpus dacrydioides and Podocarpus totara.

We tested an approach to estimate daily canopy net photosynthesis, A, based on estimates of transpiration, E, using measurements of sap flow and water-use efficiency, ω, by measuring δ13C in CO2 respired from shoots in the canopies of two conifers (Podocarpaceae) native to New Zealand. The trees were planted in adjacent 20-year-old stands with the same soil and environmental conditions. Leaf area index was lower for Dacrycarpus dacrydioides D.Don in Lamb (1.34m2m-2) than for Podocarpus totara G.Benn. ex D.Don var. totara (2.01m2m-2), but mean (± standard error) stem diameters were the same at 152±21mm for D. dacrydioides and 154±25mm for P. totara. Over a 28-day period, daily A (per unit ground area) ranged almost five-fold but there were no significant differences between species (mean 2.73±1.02 gC m-2 day-1). This was attributable to higher daily values of E (2.63±0.83mm day-1) and lower ω (1.35±0.53 gC kg H2O-1) for D. dacrydioides compared with lower E (1.82±0.72mm day-1) and higher ω (1.90±0.77 gC kg H2O-1) for P. totara. We attributed this to higher nitrogen availability and nitrogen concentration per unit foliage area, Na, and greater exposure to irradiance in the D. dacrydioides canopy compared with P. totara. Our findings support earlier observations that D. dacrydioides is more adapted to sites with poor drainage. In contrast, the high retention of leaf area and maintaining low rates of transpiration by P. totara, resulting in higher water-use efficiency, is an adaptive response to survival in dry conditions. Our findings show that physiological adjustments for two species adapted to different environments led to similar canopy photosynthesis rates when the trees were grown in the same conditions. We demonstrated consistency between whole-tree and more intensive shoot-scale measurements, confirming that integrated approaches are appropriate for comparative estimates of carbon uptake in stands with different species.

Comparison of transpiration activity of Quercus robur L. and Acer campestre L. trees under different conditions of moisture supply in the Viiskova ravine

Determining the role of trees in the water cycle and their impact on soil moisture and atmospheric humidity is crucial. This study aimed to investigate the patterns of leaf transpiration in Quercus robur and Acer campestre in a maple-oak forest under varying water supply conditions. The research was conducted in the lower third of the lower third of the north-facing slope and the middle third of the south-facing slope in the Viiskova ravine. A silvicultural and taxation survey of model trees was conducted on both sample plots, where the plantations are moderately dense. The diurnal course of transpiration patterns of these deciduous species was studied throughout the vegetation period. This physiological process reached its highest values in both species on the north-facing slope during the summer months, especially in Quercus robur. On the south-facing slope, in May and June, the average daily transpiration values in both species were almost indistinguishable. During the remaining months of the vegetation period, the intensity of water evaporation by Quercus robur leaves was statistically higher than that of Acer campestre. It was established that on the south-facing slope, under more arid conditions, this process is less active. This pertains to the daily transpiration loss of water by leaves per unit of their mass, monthly transpiration, and the intensity of this process per tree. The difference between the results of water loss by the leaves of a single Quercus robur and Acer campestre tree is significant and is attributed to the lower transpiration rate of Acer campestre, except in May and June under xerophytic conditions, as well as the smaller leaf mass of this species. Both Quercus robur and Acer campestre are hydrostable medium-transpiring species. The maple forest on the north-facing slope evaporates 30.6% more moisture per 1 ha per vegetation period than on the south-facing slope. The results obtained indicate that Acer campestre in a maple-oak forest, under fresh and dry forest-growing conditions, does not pose a significant competition for moisture for Quercus robur when they grow together. The results obtained can be used to develop effective forest management strategies in maple-oak forest

Solid humic substance enhanced spinach abiotic stress tolerance under combined drought, salinity, and daily heat stress

Spinach is a crop of economic importance in the Wintergarden region of Texas, where increasing soil salinity, irrigation water restrictions, and heat stress challenge its production. Improving abiotic stress tolerance and resource use efficiency are important goals for sustainable agricultural production. Although the effect of humic substances (HS) on abiotic stress tolerance in spinach has been evaluated under single stress, such as heat, drought, or salinity, their impact under combined abiotic stresses is unknown. We hypothesized that solid humic substances would be effective in alleviating multifactorial abiotic stress in spinach, which we examined in our first experiment, and further hypothesized that salinity stress in spinach would occur after a threshold intensity but that humic substance applications would ameliorate stress intensity past this threshold, which we examined in our second experiment. Three-week-old spinach seedlings (Spinacia oleracea L. cv. ‘Seaside’) were grown using an automatic gravimetric watering system in a climate-controlled high tunnel where daily maximum temperatures exceeded 32 °C. In a factorial experiment, we applied HS (control and 1 % v/v HS media amendment), drought (100 % and 50 % field capacity), and salinity (25 mL of RO water or 100 mM NaCl every other day) treatments. HS and HS×Salinity treatments more than doubled shoot and root FW and DW, leaf area, root length, and root surface area compared to other stresses, indicating HS improved growth and stress tolerance. Improved growth was matched with improved resource use efficiency, as HS and HS×Salinity treated plants exhibited the greatest WUE. Drought stress also increased WUE relative to the control but lowered transpiration rate responses to VPD in contrasts to HS and HS×Salinity treated plants, which increased their transpiration rates in response to increasing VPD. Salinity treatments increased sodium content (Na+) in both shoots and roots. No HS effect was observed in shoot Na+ accumulation, but HS reduced Na+ in roots under the Drought×Salinity treatment. Strong interactions between drought and salinity were observed for shoot and root Na+, Na+/K+, and shoot K+, showing that spinach accumulates Na+ and reduces K+ when drought and salinity stress are combined. HS had no apparent effect on leaf metabolites. Drought and salinity differentially impacted MDA, proline, and antioxidant content and activities, while HS showed no effect. Drought stress significantly increased MDA and proline while reducing TPC, TFC, ABTS, and FRAP. Salinity stress significantly decreased MDA, TPC, ABTS, FICA, and FRAP. In conclusion, HS improved overall spinach growth and WUE while decreasing root Na accumulation, and subsequently enhancing spinach stress tolerance.

Impact of Soil Moisture Depletion on Various Yield Components and Water Usage to Trigger Pods in Chickpea (Cicer arietinum L.) Desi Genotypes

ABSTRACTChickpeas are well adapted to rainfed conditions, but a lack of moisture during the reproductive phase can result in lower pod setting and ultimately reduced grain yield. The exact reasons for this reduction are not fully understood, partly because of the lack of information on soil moisture content (SMC) and water use during podding. This study aimed to address this knowledge gap by quantifying the impact of gradual drought on various yield components of desi‐type genotypes using the fraction of transpirable soil water (FTSW) method. Two water treatments were applied at the start of anthesis: well‐watered (WW) and drought‐stressed (DS). The WW was maintained at 24% SMC, whereas the DS was dried to 3% SMC. The results showed that DS caused early podding (3.3 days less), with reductions in plant height (11.4 cm), leaf area (1249.5 cm2), flowers (18.6), pods (27.4), seeds (37.0), grain yield (0.2 g), aboveground dry biomass (11.4 g) and harvest index (0.2 g), while increasing flower abortion (14.6) and seed biomass (1.5 g). However, diverse genotypic responses were observed to treatments, as well as water usage, FTSW and SMC that triggered pods which ranged from 1.12 to 1.89 L, 0.05 to 0.43 and 4.0% to 12.2%, respectively. A positive association between days taken and the amount of water used to terminate pods indicated that quicker‐triggering genotypes, such as Rupali and Genesis 836, consumed less water to develop pods than Flipper, ICCV_06109 and PBA Slasher did. Conversely, the negative association between the amount of water used and the number of pods triggered, seeds and grain yield explained the superior performance of Rupali and Genesis 836. These genotypes extracted less water (FTSW = 0.36 and 0.43; SMC = 10.3% and 12.2%, respectively) to develop pods and maintained favourable photosynthesis at lower transpiration rates for longer periods, allowing them to use residual moisture more efficiently. Our research offers crucial insights that can be beneficial to breeders and physiologists, paving the way for future studies aimed at developing drought‐tolerant genotypes.

Nighttime Warming Reduced Copper Concentration and Accumulation in Wheat Grown in Copper-Contaminated Soil by Affecting Physiological Traits

The changes in biomass (including yield), copper (Cu) concentration, and the accumulation of wheat (Triticum aestivum. L) in response to soil Cu pollution under nighttime warming had still not been explored. Hence, this study was carried out, and these variations were analyzed from a physiological perspective. Pot trials were performed at two levels of ambient temperatures (no-warming (NT) and average nighttime warming of 0.28 °C (WT)) and two levels of soil Cu concentrations (control check without Cu application (CK) and 100 mg/kg Cu application (Cu)). Soil was collected from the carbonate cinnamon soil region of central China. The warming effects of the passive nighttime warming system were prominent, and the average increment was 0.28 °C. Antioxidant enzyme activities were promoted by warming (p < 0.05) and Cu. The highest yield was achieved in NT-Cu, mainly attributed to relatively strong root activity and photosynthesis caused by supplemental Cu, but the Cu concentration in its grains was close to the threshold (10 mg/kg) for Cu concentration in foodstuff and could present a potential food safety risk. Though nighttime warming did not increase the total biomass and yield of wheat, it decreased the Cu accumulation of wheat grown in Cu-contaminated soil, especially in grains. Moreover, WT-CK and WT-Cu increased the Cu concentration in the roots and glumes and reduced the Cu concentration in grains by 13.09% and 55.84%, respectively, probably because of a lower transpiration rate. Among them, the Cu concentration of grains in WT-Cu was the lowest and significantly lower than other applications. Our findings reveal that nighttime warming has the potential to reduce the Cu risk of grains in wheat grown in the Cu-contaminated carbonate cinnamon soil region of central China and could then provide a theoretical reference for risk assessment of food quality for wheat subjected to dual stress from nighttime warming and Cu pollution.

Exploring genotypic diversity in sorghum breeding lines for water‐saving traits to enhance drought adaptation during the post‐rainy season

AbstractSorghum [Sorghum bicolor (L.) Moench], a crucial staple crop in South Asia and sub‐Saharan Africa, faces challenges amid increasing climate variability. Post‐rainy sorghum serves as a dominant food and fodder crop in India. Aligned with International Crops Research Institute for the Semi‐Arid Tropics's post‐rainy sorghum product profile, this research extensively characterizes sorghum lines, emphasizing the traits vital for post‐rainy drought adaptation in hybrid parents. We examined genotypic differences and trait correlations in 25 sorghum hybrid parents and varieties (B line for seed parent, R line for restorer, and check for varieties) through atmospheric and soil drought experiments. Results from atmospheric drought experiments revealed significant variation in transpiration rate (TR) under high vapor pressure deficit (VPD), with certain lines showing limited TR (BTX623 and ICSR 21002), while others exhibited high TR. In soil drought experiments, transpiration decline occurred at fractions of transpirable soil water ranging between 0.38 (ICSR 174) and 0.65 (40162 and ICSR 21005). R lines consistently displayed superior plant growth, water use, and biomass compared to B lines. Transpiration efficiency (TE) and total biomass showed positive correlations (r2 = 0.69) in well‐watered and (r2 = 0.45) in water‐stressed conditions. Most R lines displayed higher biomass and TE. Genotypes exhibiting enhanced vigor and limited TR in high VPD conditions and high TE hold potential for enhancing drought adaptation in post‐rainy sorghum. Notably, genotypes with higher biomass, lower TR, and increased TE within both R and B line groups represent valuable genetic resources for enhancing sorghum crops, post‐rainy sorghum adaptation to water deficit.

Agronomic response, transpiration and water productivity of four almond production systems under different irrigation regimes

In recent years, more intensive production systems have been developed, coinciding with a growing scarcity of water resources. This context underscores the imperative of prioritizing water productivity (WP) as a critical factor in choosing the optimal production system to minimize agricultural water use. This study aims to contribute by evaluating WP in almond orchards under four production systems: open vase with severe pruning (open vase), open vase with minimal pruning (open vase (MP)), central axis and hedgerow. Three irrigation treatments were applied over two consecutive growing seasons: fully irrigated, mild stress and severe stress. Crop transpiration was monitored over the two years using both sap flow sensors and the two-source energy balance (TSEB) model with remote sensing. The severe stress treatment exhibited a notable reduction in kernel yield and nut load of 31.6 % and 34.5 %, respectively, in the second year of water deficit. The hedgerow system tended to have similar kernel yield to the open vase (MP) and central axis systems, and higher compared to the open vase system. Additionally, both transpiration measurement methods revealed that hedgerow exhibited lower transpiration rates across all irrigation treatments. Therefore, the highest WP was observed in the hedgerow system throughout both studied years. Similar findings were derived from the analysis of long-term data. Our findings indicate that the hedgerow production system had the highest WP, averaging 0.43 kg m−3 historically, compared to 0.33 kg m−3 for the open vase, 0.34 kg m−3 for the open vase (MP), and 0.36 kg m−3 for the central axis systems.

The role of thermodiffusion in transpiration.

Plant leaf temperatures can differ from ambient air temperatures. A temperature gradient in a gas mixture gives rise to a phenomenon known as thermodiffusion, which operates in addition to ordinary diffusion. Whilst transpiration is generally understood to be driven solely by the ordinary diffusion of water vapour along a concentration gradient, we consider the implications of thermodiffusion for transpiration. We develop a new modelling framework that introduces the effects of thermodiffusion on the transpiration rate, E. By applying this framework, we quantify the proportion of E attributable to thermodiffusion for a set of physiological and environmental conditions, varied over a wide range. Thermodiffusion is found to be most significant (in some cases > 30% of E) when a leaf-to-air temperature difference coincides with a relatively small water vapour concentration difference across the boundary layer; a boundary layer conductance that is large as compared to the stomatal conductance; or a relatively low transpiration rate. Thermodiffusion also alters the conditions required for the onset of reverse transpiration, and the rate at which this water vapour uptake occurs.

Elevated CO2-conferred sodium homeostasis is linked to abscisic acid-mediated stomatal closure and signalling pathway in tomato plants

Soil salinity hampers plant performance. Elevated atmospheric CO2 (e[CO2]) could alleviate the detrimental effect of salinity on plants but whether abscisic acid (ABA) is involved in this process is unclear. To address this issue, three tomato (Solanum lycopersicum) genotypes with varying endogenous ABA concentrations (wild-type AC, ABA-deficient mutant flacca and ABA-overproduction line SP5) were grown in pots under ambient (400 μmol · mol–1) or elevated (800 μmol · mol–1) CO2 with or without the addition of 100 mmol · L−1sodium chloride (NaCl). The results showed that e[CO2] favored ion homeostasis by decreasing root-to-shoot delivery of Na+, which was mainly attributed to lowered transpiration rate rather than altered xylem-sap Na+ concentration. In AC and SP5, the low transpiration rate of e[CO2]-plants under salinity was accompanied by enhanced endogenous ABA levels, which might play a role in upregulating the abundance of specific transcripts related to Na+ homeostasis (i.e., SALT OVERLY SENSITIVE) under salt stress. In flacca, e[CO2]-induced Na+ homeostasis was abolished, which could be ascribed to the low and unaltered ABA levels, albeit the ethylene biosynthesis was enhanced in flacca under salt stress, indicating an antagonistic relationship between ABA and ethylene. Furthermore, e[CO2] inhibited ethylene biosynthesis under salt stress in all three genotypes. The results enrich our comprehension of the fundamental processes of e[CO2]-conferred salt tolerance in tomato.

Effect of a QTL on wheat chromosome 5B associated with enhanced root dry mass on transpiration and nitrogen uptake under contrasting drought scenarios in wheat.

A sufficient nitrogen supply is crucial for high-quality wheat yields. However, the use of nitrogen fertilization can also negatively influence ecosystems due to leaching or volatile atmospheric emissions. Drought events, increasingly prevalent in many crop production areas, significantly impact nitrogen uptake. Breeding more efficient wheat varieties is necessary to achieve acceptable yields with limited nitrogen and water. Crop root systems play a crucial role as the primary organ for absorbing water and nutrients. To investigate the impact of an enhanced root system on nitrogen and water use efficiency in wheat under various irrigation conditions, this study conducted two experiments using precision phenotyping platforms for controlled drought stress treatment. Experiment 1 involved four contrasting winter wheat genotypes. It included the Chinese variety Ning0604, carrying a quantitative trait locus (QTL) on chromosome 5B associated with a higher root dry biomass, and three elite German varieties, Elixer, Genius, and Leandrus. Experiment 2 compared near-isogenic lines (NIL) of the three elite varieties, each containing introgressions of the QTL on chromosome 5B linked to root dry mass. In both experiments, nitrogen partitioning was tracked via isotope discrimination after fertilization with 5 Atom % 15N-labeled KNO3-. In experiment 1 the quantification by 15N isotope discrimination revealed significantly (p < 0.05) higher nitrogen derived from fertilizer in the root organ for Ning0604 than those of the three German varieties. In experiment 2, two out of three NILs showed a significantly (p < 0.05) higher uptake of N derived from fertilizer than their respective recipient line under well-watered conditions. Furthermore, significantly lower transpiration rates (p < 0.1) were observed in one NIL compared to its respective recipient. The combination of the DroughtSpotter facility coupled with 15N tracer-based tracking of N uptake and remobilization extends the insight into the impact of genetically altered root biomass on wheat NUE and WUE under different water availability scenarios. The study shows the potential for how a modified genetic constitution of the locus on wheat chromosome 5B can reduce transpiration and enhance N uptake. The dependence of the observations on the recipient and water availability suggests a need for further research to investigate the interaction with genetic background traits.

Direct numerical simulations of turbulent channel flow with wall transpiration using lattice Boltzmann method

Abstract Direct numerical simulations of turbulent channel flow with wall transpiration are conducted using the multi-relaxation time lattice Boltzmann method for the first time. Flows with two friction Reynolds numbers, $Re_\tau$ = 150 and 250, are investigated, and the explored transpiration rates based on the friction velocity range from 0.05 to 0.26. A successive block mesh-refinement strategy is adopted to resolve the near-wall structure, where the grid sizes are $\Delta ^+ \sim$1, 2, and 4. Under such resolution, the size of the maximum grid density employed is $775 \times 10^6$. At the low transpiration rate ($V^+=0.05$), the turbulence level at the suction side is damped relative to the less altered values along the injection side. However, at the high level of wall transpiration, i.e. $V^+=0.26$, turbulence levels are severely retarded on both the injection and suction sides. The predicted mean and turbulence quantities show good agreements with the available direct numerical simulation data, indicating the effectiveness of lattice Boltzmann method combined with mesh refinement in reproducing the correct physics of turbulent channel flows with different levels of wall transpiration.

Preference of Silicon Accumulation on the Shade Foliage of Tree Crown and its Implication in Juniperus chinensis L.

PurposeThe passive accumulation of silicon (Si) generally depends on the regulation of plant transpiration rates after its uptake. It is challenging to comprehend how plants use Si to adapt to shady habitats where they have low transpiration rates and photothermal energy. Therefore, we speculated that Si accumulation is not entirely dependent on the transpiration rate.MethodsTo test this speculation, the concentrations of Si and total minerals and water status at various positions of shady shoots (stems and their foliage) and stems within the crown of Juniperus chinensis L. were examined to determine whether shady shoots or stems had a preferred allocation to resist shade.ResultsThe concentrations of total minerals and Si in the shoots were consistently higher in shady areas than in areas within the same crown, regardless of the position within the crown or shoot age. However, shoot Si accumulation displayed a greater dependence on available light or photothermal supply, which is linked to crown orientation. Additionally, stem Si accumulation displayed a weak dependence on available light. Compared with the bound water content, the water potential and free water content of shady shoots were higher than those of sunny shoots. In light of the fact that water prefers to move readily towards regions with low water potential, these results demonstrate that the movement of minerals and water is not fully coupled in the same crowns.ConclusionTherefore, the accumulation of Si and minerals in shady foliage is partially independent of water flow, which helps to offset the low-carbon supply due to the photothermal decrease in the shady crown area.

Comparison of Physiological, Anatomical, and Morphological Traits between Sugarcane Hybrids and Their Parents with Different Stalk Dry Weights in the Early Growth Stage under Hydroponic Conditions

The high stalk weight sugarcane cultivar has a special mechanism to obtain greater growth, which was inherited from its parents. Thus far, comparisons of the high stalk weight sugarcane cultivar growth with its parents and cultivars with a low stalk weight have never been reported. The purpose of this research was to reveal the growth mechanism of the high stalk dry weight cultivar KK3 by comparing its physiological, anatomical, and morphological traits to those of a low stalk dry weight cultivar (UT12) and their four parental cultivars under hydroponic conditions. Their growth characteristics were evaluated at 15-day intervals from 30 to 90 days after planting. The root traits were measured at 2 months after planting (MAP), whereas the anatomical and physiological parameters were collected at 3 MAP. Biomass was recorded at 1, 2, and 3 MAP. KK3 had similar anatomical root traits to its female parent, whereas it had similar aboveground morphological traits to its male parent. The comparison between UT12 and its parents revealed that almost all its root anatomical traits were similar to the female parent, but it did not differ in leaf anatomy and root system size. Some physiological traits of KK3 were not different from those of its parents. In contrast, the net photosynthesis rate (PN), height, tiller number, stem dry weight, and stomatal density of UT12 were lower than those of its parent. For KK3, its small root stele and vessel size and high root length, surface area, and volume supported water uptake. The increase in stomatal density and decreased stomatal pore length may be appropriate characteristics for reducing water loss in this drought-resistant cultivar. Furthermore, KK3 exhibited a high water use efficiency (WUE) to promote biomass accumulation and growth despite its low transpiration and photosynthesis rates. This basic knowledge will be useful for selecting the parents based on their characteristics to create new sugarcane cultivars with a high stalk dry weight for drought stress during the early-growth-stage breeding programs and predicting their performance.

Aquaporins-mediated water availability in substrates for cannabis cultivation in relation to CBD yield

Abstract Aims The objective of this study was to identify the most suitable substrate for Cannabis sativa L. cultivation based on its effects on water relations and Cannabidiol (CBD) production. Methods Biomass, physiological parameters, minerals, changes in the expression levels of plasma membrane intrinsic Proteins (PIP) and CBD concentration was measured in C. sativa (var. Tiborszallasi) plants cultivated on 5 substrates with different physical–chemical characteristics. Results The substrates available water (AW) was the main factor affecting growth and production. The efficiency of the water use was governed fundamentally by transpiration. Experimental substrates(S) 1 and 3 (S1 and S3) were those in which the plants grew optimally and allows plants to invest energy in secondary metabolites production acquiring high levels of CBD. The plants grown in S2 and S5, composed by coconut fiber and perlite, showed the lowest growth in agreement with low transpiration rates which reduce the water uptake. S5 substrate, with some available water (AW) still present, is forcing plants to invest energy in improving water and nutrient transport, as observed by the high levels of nutrients in planta and PIPs expression levels. S4 plants presented the highest inflorescence production and CBD content, which can be attributed to plant stress due to the low levels of AW and high pH and electrical conductivity (EC). Conclusion The absorption of water and minerals by plants has been affected by PIP-mediated water transport, playing key roles for the optimal utilization of the water present in the substrates, with specific isoforms involved in these responses.

Genetic variation and correlations for some physiological characters and seed yield in Indian mustard (Brassica juncea L.) under rainfed conditions

An experiment was conducted with 42 Indian mustard genotypes in Randomized Complete Block design to estimate genetic parameters and correlations of some physiological characters and seed yield under rainfed conditions. Specific leaf area, transpiration rate and relative water content were recorded at 30 (vegetative stage), 45-50 (50% flowering stage) and 60-65 days aftersowing (full flowering stage). Total drymatter, harvest index, pod intensity, pod area on main and primary branches, seed : husk ratio and seed yield were recorded at the time of harvest. The analysis of variance indicated highly significant differences among the genotypes for all the characters studied. The maximum phenotypic and genotypic variability was observed for transpiration rate at full flowering stage. Heritability estimates in broad-sense were high for all the characters except relative water contents (RWC) at all the 3 stages, pod area of main and primary branches and pod intensity on main shoot. High heritability combined with high genetic advance was observed for specific leaf area at all the 3 stages, transpiration rate at 50%and fullflowering and total drymatter/plant suggested scope for selection for these characters owing to predominance of additive effects in the expression of these characters. Seed yield/plant had significant and positive correlations with harvest index (r = 0.581**), total drymatter/plant (r = 0.869**), pod intensity on main shoot (r = 0.467**), pod area of main (r = 0.536**) and primary branches ((r = 0.317*) and RWC at all the 3 developmental stages. Thus, selection for high harvest index, total dry matter/plant and pod intensity coupled with low transpiration rate at flowering stage, resulting in maintenance of high RWC in leaves, should be emphasized to increase yield under rainfed conditions.

Testing transpiration rates of juvenile Aleppo pine trees using the heat ratio method under laboratory conditions

AbstractTree transpiration considerably contributes to evaporative fluxes to the atmosphere in terrestrial ecosystems. Accurate transpiration quantification provides relevant information about forest water use and may benefit adaptive forest management, especially in a global change context. Tree transpiration can be measured by several methods, and sap flow measurements are one of the most valued. However, species‐specific validations of these techniques are required to avoid undesirable bias. This is especially relevant in species with low transpiration rates where errors may be relevant, such as Aleppo pine trees (Pinus halepensis Mill.). Moreover, another significant source of uncertainty in sap flow measurements is probe misalignment. Hence, the aim of this study was to correlate transpiration rates estimated by sap flow probes using the heat ratio method (THRM) and load cells to independently monitor water transpiration in juvenile Aleppo pine trees. The corrections to improve transpiration measures, including misalignment correction, were applied to THRM results to test if the accuracy of results improved. These measurements were recorded in greenhouse under controlled conditions to implement different environmental conditions. The environmental variables that ruled the experiment, mainly vapour pressure deficit and soil water availability, spanned in a wide range of values. The results showed an accurate linear correspondence between TOBS and THRM for low and medium values, but moderate underestimations at high transpiration rates were observed. These underestimations were partly removed when applying probe misalignment correction. This study supports the notion that HRM offers accurate Aleppo pine transpiration estimations with low and medium values under a variety of abiotic conditions, which also has implications for HRM application in other isohydric species. The results also support the interest in the use of probe misalignment correction to estimate transpiration, mainly when high transpiration values are recorded. The results of this study can be considered as a preliminary approach for future research in order to improve the estimates of the transpiration rates of the Aleppo pine under the limiting conditions of the Mediterranean.

Genome-material costs and functional trade-offs in the autopolyploid Solidago gigantea (giant goldenrod) series.

Increased genome-material costs of N and P atoms inherent to organisms with larger genomes have been proposed to limit growth under nutrient scarcities and to promote growth under nutrient enrichments. Such responsiveness may reflect a nutrient-dependent diploid versus polyploid advantage that could have vast ecological and evolutionary implications, but direct evidence that material costs increase with ploidy level and/or influence cytotype-dependent growth, metabolic, and/or resource-use trade-offs is limited. We grew diploid, autotetraploid, and autohexaploid Solidago gigantea plants with one of four ambient or enriched N:P ratios and measured traits related to material costs, primary and secondary metabolism, and resource-use. Relative to diploids, polyploids invested more N and P into cells, and tetraploids grew more with N enrichments, suggesting that material costs increase with ploidy level. Polyploids also generally exhibited strategies that could minimize material-cost constraints over both long (reduced monoploid genome size) and short (more extreme transcriptome downsizing, reduced photosynthesis rates and terpene concentrations, enhanced N-use efficiencies) evolutionary time periods. Furthermore, polyploids had lower transpiration rates but higher water-use efficiencies than diploids, both of which were more pronounced under nutrient-limiting conditions. N and P material costs increase with ploidy level, but material-cost constraints might be lessened by resource allocation/investment mechanisms that can also alter ecological dynamics and selection. Our results enhance mechanistic understanding of how global increases in nutrients might provide a release from material-cost constraints in polyploids that could impact ploidy (or genome-size)-specific performances, cytogeographic patterning, and multispecies community structuring.