Crop Ecophysiology: From Lab to Field

Maize is essential in ensuring food security in China as a primary food and feed crop. One of the main ways to increase yield in maize production systems is to increase planting density as appropriate. Clarifying the relationship between planting density and grain nutritional quality can provide theoretical guidance for high-yielding high-quality maize cultivation and management practices. To this end, five representative high-yielding maize varieties from the 1970s to the 2010s in China were used as experimental material, and two planting densities of 45,000 plants hm⁻² and 105,000 plants hm⁻² were set to analyze the changing patterns of yield traits and grain nutrient quality of maize varieties in different eras, as well as their responses to densification conditions. The results showed that, under low-density conditions, the grain nutrient quality components of the 2010s’ variety (DH618) were all different 75 days after anthesis compared with the 1970s’–2000s’ varieties and yields also significantly increased by 11.15% to 19.18% (p < 0.05). The increase in planting density led to a rise in total grain starch and soluble sugar content 75 days post-anthesis in all varieties from the 1970s to the 2010s, with increases of 0.65–1.65% and 39.44–69.01%, and a decrease in crude grain protein and crude fat content, with reductions of 4.15–8.50% and 3.00–11.18%. The increase in total grain starch content 75 days post-anthesis was mainly due to the rise in grain starch accumulation between 23 and 47 days post-anthesis in the 1970s’–2010s’ varieties, with an increase of 7.72–9.19% in all varieties. The higher accumulation of crude fat and soluble sugar in the 0–23 days post-anthesis period also contributed to the increase in total starch accumulation in the 23–47 days post-anthesis period. Ultimately, densification conditions also contributed to a significant increase in yield across all eras of the varieties based on changes in grain nutritional quality, with a more significant increase in yield due to densification and a smaller decrease in grain crude fat content due to densification 75 days after anthesis in the 2010s’ variety (DH618). Therefore, in cultivation and production processes that do not have specific requirements for the nutritional quality components of maize grain, we suggest that the use of a representative high-yielding maize variety (DH618) from the 2010s, together with appropriate planting at close planting distances, can significantly increase maize yields based on an increase in the total starch content of the grain at physiological maturity. Full article

In order to explore the changes in biochemical components and mechanical properties of cucumber seedlings with dwarfing characteristics under airflow disturbance treatment, ‘Jinyou No. 1’ cucumber seedlings were used as experimental materials and the split-plot design was used. The cucumber seedlings were treated with airflow disturbance with two airflow temperatures of 25 ± 5 °C and 35 ± 5 °C as the main factors and four airflow velocities of 1, 3, 6 and 9 m/s as the secondary factors. At the same time, cucumber seedlings without airflow disturbance were used as controls to study the effects of airflow temperature and velocity on the biochemical components and mechanical properties of cucumber seedling stems. The results showed that with the increase in airflow velocity, the content of the stems’ biochemical components increased to varying degrees, and the bending load, shear load, elastic modulus, bending strength and shear strength of the seedling stems also increased. Under the same airflow velocity, the biochemical component content and the accepted load of seedlings under the 25 ± 5 °C airflow temperature treatment were larger than those under the 35 ± 5 °C airflow greenhouse treatment, but the elastic modulus, bending strength and shear strength of seedlings under the 25 ± 5 °C airflow temperature treatment were lesser than those under the 35 ± 5 °C airflow temperature treatment. Using the grey relational analysis method, the correlation degree between the biochemical components of the stem and the mechanical properties of the stem was different. The correlation degree between the biochemical components of the seedling stem and the mechanical properties under different airflow temperature treatments was significant. The correlation degree between the biochemical components of the seedling stem and the mechanical properties under different airflow velocity treatments was greater than 0.60, indicating that the biochemical components of the seedling stem under airflow velocity treatments had a greater influence on the mechanical properties. In summary, airflow disturbance significantly affected the biochemical components and mechanical properties of cucumber seedlings. The biochemical components and mechanical properties of seedlings were negatively correlated with airflow temperature and positively correlated with airflow velocity. With a decrease in airflow temperature and an increase in airflow velocity, the biochemical components and mechanical properties of seedlings increased. Full article

Soil waterlogging is one of the most serious abiotic stresses on plant growth and crop productivity. In this study, two potassium application levels (0 and 150 kg K₂O hm⁻²) with three types of soil waterlogging treatments (0 d, 3 d and 6 d) were established during cotton flowering and boll-forming stages. The results showed that soil waterlogging markedly reduced RWC (relative water content), gas exchange parameters and cotton biomass. However, potassium application considerably improved the aforementioned parameters. Specifically, 3 d soil waterlogging with potassium increased Pn (net photosynthetic rate), Gs (stomatal conductance), Ci (intercellular CO₂ concentration) and Tr (transpiration rate) by 4.55%, 27.27%, 5.74% and 3.82%, respectively, compared with 3 d soil waterlogging under no potassium, while the abscission rate reduced by 2.96%. Additionally, the number of bolls and fruit nodes under 6 d soil waterlogging with potassium increased by 16.17% and 4.38%, compared with 6 d soil waterlogging under no potassium. Therefore, it was concluded that regardless of 3 d or 6 d soil waterlogging, potassium application alleviated the negative effects of waterlogging by regulating the plant water status, photosynthetic capacity and plant growth in cotton. These results are expected to provide theoretical references and practical applications for cotton production to mitigate the damage of soil waterlogging. Full article

Changes of water-soluble carbohydrate (WSC) content such as fructose, glucose, sucrose, maltose, nystose, raffinose, stachyose and fructan were analyzed in wheat kernels in Fusarium epidemic and non-epidemic seasons. In both season types, eight commercial fungicides were applied and three wheat varieties with differing Fusarium resistance were tested. In the epidemic year, the average total amount of WSC was above 1.6% which was 2 times higher than in the non-epidemic year (0.7%). Sucrose, maltose, raffinose and fructan components determined the increased WSC value, but the most substantial change was observed in maltose content where its average amount was 28 times higher in the epidemic year. Fungicide application also significantly increased all the carbohydrate components except maltose, where significant reduction was observed. WSC components had strong correlation with several farinograph or extensograph parameters, but only the maltose content showed positive strong correlation (r = 0.9) with deoxynivalenol (DON) toxin that was highly affected by the applied fungicide. The changes of WSC indicate altered carbohydrate synthesis along with abnormal degradation processes and thus have impaction on the baking features. It seems that the sugar metabolism interacts with DON synthesis and the results give important additional information to the altered metabolism of the attacked plant. Full article

One of the promising trends in modern agronomy is the development of automated closed urban vertical farms with controlled environmental conditions, which can improve dynamics of the crop vegetation process. In the frame of this work, the analysis of the vegetative stages of potato seed material (minitubers and microplants) grown in the conditions of the automated vertical farm was conducted. The study was performed at the vertical farm of the Federal Research Center “Fundamentals of Biotechnology” of the Russian Academy of Sciences by the analysis of water consumption dynamics. It was established that the 20-day reduction in the vegetative period of the vertical-farm-grown potatoes in comparison with the field-grown ones occurred due to the reduction in the final stage of vegetation (mass gain of newly formed tubers) under the minitubers planting. The same reduction occurred due to both final and initial vegetative stage (absence of tubers germination) under the planting of microplants. The obtained result shed new light on the vegetation dynamics of potato grown under controlled conditions of the urban vertical farms and demonstrated a possibility to perform the study of plant development process using automated diagnostics systems of vertical farms. Full article

Meteorological factors are one of the important factors that determine maize kernel weight and grain nutritional quality. Analyzing the influence of meteorological factors before and after anthesis on maize kernel weight and nutritional quality components is of great significance for improving corn yield and quality. Therefore, five different maize hybrids and conducted continuous experiments from 2018 to 2021 were selected in this study, to explore the response of maize kernel weight and grain nutritional quality to meteorological factors in different growth periods, and to quantify the linear relationship between grain nutritional quality parameters, grain weight, and meteorological factors. The main results were as follows: the 100-grain weight reached the maximum value of 39.53 g in 2018; the contents of crude protein, total starch, and crude fat in grains reached the maximum in 2018, 2020, and 2018, respectively, which were 9.61%, 69.2%, and 5.1%. Meteorological factors significantly affected the maize grain weight (p < 0.05). Before anthesis, total sunshine duration, average temperature, relative humidity, and the accumulated temperature had strong effects on grain weight. After anthesis, average daily temperature, total rainfall, temperature difference, accumulated temperature, average daily highest temperature, and total sunshine hours had strong effects on grain weight. There was also a significant correlation between grain weight and grain nutritional quality components (p < 0.05). The multivariate polynomial equation analysis revealed that further potential for maize grain weight could be exploited by adjusting the content of each quality component of the kernels under the current test conditions. Meteorological elements can indirectly affect the 100-grain weight through their relationship with the nutritional quality of the grains, with accumulated temperature before anthesis, average temperature after anthesis, and accumulated temperature after anthesis having the greatest indirect effect on the 100-grain weight. Therefore, the effects of pre-anthesis accumulation temperature, post-anthesis average temperature, and post-anthesis accumulation temperature on the nutritional quality of the grains can be harmonized by the application of hybrids of different lengths of vegetation and by adjusting the sowing time in agricultural production. Ultimately, maize grain weight can be increased on the basis of optimizing the content of various quality components in the grains. Full article

Changes in sugar composition occur continuously in plant tissues at different developmental stages. Tuber dormancy induction, stability, and breaking are very critical developmental transitions in yam crop production. Prolonged tuber dormancy after physiological maturity has constituted a great challenge in yam genetic improvement and productivity. In the present study, biochemical profiling of non-structural sugar in yam tubers during dormancy was performed to determine the role of non-structural sugar in yam tuber dormancy regulation. Two genotypes of the white yam species, one local genotype (Obiaoturugo) and one improved genotype (TDr1100873), were used for this study. Tubers were sampled at 42, 56, 87, 101, 115, and 143 days after physiological maturity (DAPM). Obiaoturugo exhibited a short dormant phenotype and sprouted at 101-DAPM, whereas TDr1100873 exhibited a long dormant phenotype and sprouted at 143-DAPM. Significant metabolic changes were observed in non-structural sugar parameters, dry matter, and moisture content in Obiaoturugo from 56-DAPM, whereas in TDr1100873, significant metabolic changes were observed from 101-DAPM. It was observed that the onset of these metabolic changes occurred at a point when the tubers of both genotypes exhibited a dry matter content of 60%, indicating that a dry matter content of 60% might be a critical threshold for white yam tuber sprouting. Non-reducing sugars increased by 9–10-fold during sprouting in both genotypes, which indicates their key role in tuber dormancy regulation in white yam. This result implicates that some key sugar metabolites can be targeted for dormancy manipulation of the yam crop. Full article

The application of pulp and paper mill sludge to agricultural soils is commonly considered as a strategy to improve soil properties, promote plant growth, and reduce the demand for costly chemical fertilization. The aim of this study was to evaluate if sodium lignosulfonate (sLS), one of the sludges of pulp production, may affect the biomass production, the respiration (R) and net CO₂ assimilation rate (A_n) at the leaf level, and the content and accumulation of trace elements in the leaves of cucumbers grown under a sufficient nutrient supply or soil nutrient deficit. A pot culture experiment was conducted using sLS application rates of 0, 1.0, 2.5, 5.0, and 10 vol% to sandy loam soil. The decline in nutrient availability caused an increase in the R/A_n ratio and dramatically depressed biomass accumulation. The leaf Fe, Ni, Cr, Co, Al, and Pb contents were lower under low nutrient availability than under sufficient nutrient supply. Although sLS was not very effective in lessening the negative effect of nutrient deficiency on biomass accumulation, it reduced respiratory carbon losses and cell membrane permeability in the leaves of cucumbers grown under nutrient deficit. The reduction in the toxic level of leaf Mn in seedlings grown under sufficient nutrient availability and the toxic level of leaf Fe under a nutrient deficit might also be considered as a positive effect of the sLS application to sandy soil. Full article

Priming involves the exposure of plants to a mild stress to increase tolerance to a more intense stress in the future. Chemical priming with brassinosteroids reduces the negative effects of flooding on the physiology and survival of some plant species. Avocado trees are very susceptible to flooding, and flooding susceptibility is related to the rootstock, which is often derived from seeds. In this study, the effects of chemical priming with two brassinosteroids, 28-homobrassinolide or 24-epibrassinolide, to improve the tolerance of avocado (Persea americana Mill.) trees to short-term flooding was assessed in two separate experiments with seedling trees of avocado cultivars Monroe (Experiment 1) and Reed (Experiment 2). In each experiment, trees were treated with a soil drench of 28-homobrassinolide, 24-epibrassinolide, or deionized water as a control. Trees in each chemical treatment were divided into two flooding treatments: flooded by submerging potted trees in water to above the soil surface or nonflooded. After the flooding treatments had begun, we measured the leaf gas exchange (net CO₂ assimilation (A), stomatal conductance (g_s), transpiration (Tr) and water use efficiency (WUE)) and the maximal potential quantum efficiency of photosystem II (the ratio of variable to maximum chlorophyll fluorescence; Fv/Fm) daily during the flooding period as indicators of plant stress. After the trees had been unflooded, leaf gas exchange and Fv/Fm were measured periodically during the recovery period. In both experiments, flooding reduced leaf gas exchange and Fv/Fm of trees in the chemical control and 28-homobrassinolide treatments beginning 2–3 days after flooding began until the end of the experiment. However, there was a negligible effect of flooding on leaf gas exchange or Fv/Fm of trees treated with 24-epibrassinolide. In both experiments, a greater percentage of the flooded plants treated with 24-epibrassinolide survived compared to plants in the two other chemical treatments. The results of this study indicate that pretreatment (priming) with 24-epibrassinolide as a soil drench prior to flooding reduces flooding stress of avocado trees. Full article

Cotton has a high salt tolerance. However, due to the high salt content and low K⁺/Na⁺ ratio in saline soils, cotton yield and fiber quality are difficult to improve. To investigate the effects of potassium (K) on cotton fiber length under salt stress, a two-year bucket-based field experiment was conducted using two different cultivars (CCRI 79, salt tolerant, and Simian 3, salt sensitive). Three K rates (K0, 0 kg K₂O ha⁻¹; K150, 150 kg K₂O ha⁻¹; and K300, 300 kg K₂O ha⁻¹) were applied at low, middle, and high soil electrical conductivities (S1, 1.7–1.8 dS m⁻¹; S2, 6.4–6.9 dS m⁻¹; and S3, 10.6–11.8 dS m⁻¹) to investigate the absorption, transport, and distribution characteristics of K⁺ and Na⁺ in the boll-leaf system (including the leaf subtending the cotton boll (LSCB), fruiting branch, boll shell, and fiber) of both cotton cultivars, as well as the relationship with fiber length. The results showed that K application (K150 and K300) significantly increased the cotton fiber length under salt stress, with the largest fiber length alleviation coefficients (AC) in the middle fruiting branches. The AC decreased with an increase in salt stress and was greater in CCRI 79 than in Simian 3. The K150 treatment (soil K⁺/Na⁺ = 1/13) completely mitigated the reduction in fiber length caused by S2 salt stress in CCRI 79, whereas the K300 treatment (soil K⁺/Na⁺ = 1/10) completely eased the reduction in fiber length caused by S2 salt stress in Simian 3. An application of K under salt stress increased the K⁺ content and K⁺/Na⁺ ratio in the soil and the organs of the boll-leaf system, regulated the K⁺/Na⁺ homeostasis in the boll-leaf system, enhanced the K⁺-selective transport coefficient (S_K-Na) in the LSCB, maintained a high K⁺/Na⁺ ratio in the fiber, and mitigated the fiber length reduction. In conclusion, the fiber length reduction in salt-tolerant cultivars was completely mitigated by K150 (i.e., soil K⁺/Na⁺ = 1/13) under moderate salt stress; however, it was not completely mitigated by K application under high salt stress. Full article

Intraspecific trait variation is a critical determinant of ecosystem processes, especially in agroecosystems where single species or genotypes exist in very high abundance. Yet to date, only a small number of studies have evaluated if, how, or why traits forming the Leaf Economics Spectrum (LES) vary within crops, despite such studies informing our understanding of: (1) the environmental factors that drive crop LES trait variation and (2) how domestication has altered LES traits in crops vs. wild plants. We assess intragenotype variation in LES traits in ‘Chardonnay’ (Vitis vinifera)—one of the world’s most commercially important crops—across a soil compaction gradient: one of the most prominent characteristics of agricultural soils that may drive crop trait variation. Our early evidence indicates that ‘Chardonnay’ traits covary along an intragenotype LES in patterns that are qualitatively similar to those observed among wild plants: resource-acquiring vines expressed a combination of high mass-based photosynthesis (A_mass), mass-based dark respiration (R_mass), and leaf nitrogen concentrations (N), coupled with low leaf mass per area (LMA); the opposite set of trait values defined the resource-conserving end of the ‘Chardonnay’ LES. Traits reflecting resource acquisition strategies (A_mass, R_mass, and leaf N) declined with greater bulk density, while traits related to investment in leaf construction costs (LMA) increased with greater bulk density. Our findings contribute to an understanding of the domestication syndrome in grapevines and also provide information relevant for quantifying trait-based crop responses to environmental change and gradients. Full article

Crops are grown in natural conditions. Environmental factors such as temperature, humidity, and light irradiance have a regular pattern. A grower chamber is usually used to test the effect of environmental factors on the crops. If crops were cultivated under fixed environmental conditions, the results would be different from that for plants that are grown in a natural environment. Limits in the capability of an apparatus mean that most studies use a fixed temperature, a fixed relative humidity, or a fixed light intensity. In an accumulated temperature study, Pak choi and strawberry were used to compare the difference between fixed and oscillating temperature conditions in a growth chamber. There were three temperature patterns: the high-temperature (HVT) oscillation pattern (day: 22–32 °C; night: 19–25 °C), low-temperature (LVT) oscillation pattern (day: 21–29 °C; night: 19–23 °C), and the fixed temperature (CT) regime (day: 25 °C; night: 22 °C). The light intensity was 80 μmol∙m⁻²s⁻¹. The environments used for the Pak choi experiments were the HVT oscillation pattern, the CT pattern, and the inside air temperature for a net house. The strawberries had three treatments: the HVT and LVT oscillation patterns, and the CT pattern. The fresh weight of total plants, the leaf area, the leaf number, and the chlorophyll content were measured for the two crops. For strawberries, the fresh weight of the leaves and the Brix value were measured. The experimental results show that there is a significant difference in the growth characteristics for these three regimes. The results of the growth characteristics of Pak choi and strawberry for an oscillating temperature are better than those for a fixed temperature environment with a statistically significant difference. For the biological and agricultural experiments, an oscillating temperature in the growth chamber realistically simulates a natural environment. Full article

High grain water content at harvest stage is the main limiting factor for realizing mechanized maize grain harvest in China. Under the background of yield gain by density increase, it is necessary to clarify the effect of planting density increase on maize grain dehydration characteristics, which would provide theoretical support for realizing mechanized grain harvest under high planting density conditions. Therefore, this study selects five main hybrids, ZD2, DY13, YD13, XY335, and DH618, released in different eras that were widely promoted in Inner Mongolia from the 1970s to 2010s. The experiment was conducted in the Chilechuan Modern Agriculture Expo Park, Tumed Right Banner, Baotou city, Inner Mongolia, in 2018 and 2019. Under the three densities of 45,000 plants ha⁻¹ (low density), 75,000 plants ha⁻¹ (medium density) and 105,000 plants ha⁻¹ (high density), the indexes of grain dehydration, leaf stay-green, bract and cob dehydration of the different maize hybrids were measured and analyzed. The results show that MCpm (moisture content at physiological maturity) of hybrids in the 1970s and 1990s was significantly reduced by 1.57 and 1.14 percentage points, respectively, and MCh (moisture content at harvest time) in the harvest period of hybrids in the 1970s was significantly reduced by 0.99 percentage points, from a low to medium density. The GDRbm (rate of grain dehydration before maturation) and the GDRam (rate of grain dehydration after maturation) showed an increasing trend from a low to medium density. From a medium to high density, the MCpm from the 1980s to 2000s could be significantly reduced by 1.78, 1.53 and 1.88 percentage points; the MCh from the 1980s could be significantly reduced by 1.77 percentage points; and the GDRbm from the 1970s was significantly increased by 0.101%/d, but the improvement of GDRam was not significant. With the planting density increase, the decreased ratios of relative GLAD (green leaf area duration) and leaf SPAD (soil and plant analyzer development) per plant of old maize hybrids were more than that of modern maize hybrids, which promoted the decrease in grain water content and the rate increase in grain dehydration for old maize hybrids. There was a direct positive correlation between the bract and grain dehydration rates, but the cob dehydration rate had no significant effect on the grain dehydration rate. With the increase in planting density, the relative GLAD and leaf SPAD values of plants decreased, and the stay-green of plants worsened, and a significant increase in the dehydration rate of bracts in old and modern eras was an important reason for the decrease in grain moisture content and increase in dehydration rate. Full article