Full-grown Artemisia annua plants were subjected to chemical and physical stress conditions, and the effect of these on the concentration and chemical composition of essential oil components (EOC) in the leaves was studied. The chemical stress treatments were performed by foliar application of NaCl, H₂O₂, salicylic acid and chitosan oligosaccharide (COS). The EOC of the leaves were extracted with n-hexane and identified and quantified by GC–MS and GC–FID, respectively. Approximately 96 % of EOC in the extracts were identified and quantified of which β-pinene, camphene, germacrene D, camphor, coumarin and dihydro-epi-deoxyarteannuin B were the major EOC accounting for about 75 % of the total content of EOC in the extracts. The physical stress treatment, sandblasting of the plants resulted in a significant enhancement in the content of α-pinene, camphene, coumarin and dihydro-epi-deoxyarteannuin B. The total yield of identified EOC in non-treated plants (control) was 86.2 ± 13.8 μg g⁻¹ fresh weight (FW) compared with 104.0 ± 9.1 μg g⁻¹ FW in sandblasted plants. The chemical stress treatments did not affect the composition of EOC significantly. The results indicate that chemical stress treatments do not affect the concentration and composition of EOC in full-grown A. annua plants to the same extent as physical stress treatment by sandblasting.

The study investigated the cultivars of non-obligatorily requiring vernalization plant Festulolium braunii and assessed the influence of non-hardy reproductive and hardy vegetative structures on overwintering effect. The study was conducted taking into account systemic relations between these types of structures. The results show the cultivars differ according to the percentage of headed and overwintered plants, when the cultivars with the most abundant heading – ‘Felopa’ and ‘Sulino’ – are also better at overwintering. The positive correlation between heading and overwintering characteristics was also observed, what seemed to be a rather new finding. It can be explained by systemic effect: non-hardy later reproductive structures induce the post-generative regrowth of vegetative shoots, which during shorter days halt development and become potentially hardy. More detailed interpretation is also provided including discussion of causal mechanisms of the detected phenomenon. The authors suppose that these mechanisms constitute a survival strategy for such perennial plants. The observed late heading which represents reproductive structures could be applied in plant breeding as a marker of winter-hardiness among perennial grass plants which non-obligatorily demand vernalization.

Spikelet sterility in rice (Oryza sativa L.) induced by high temperatures is a major concern given global warming predictions. We studied differences among eight rice cultivars in spikelet fertility at five different temperature levels in temperature gradient chamber (TGC) experiments. Six japonica and two indica cultivars were exposed to high-temperature gradients in TGCs during the 2005 flowering season. Spikelet sterility increased with temperature in TGCs and differed among cultivars because of both variations in temperature tolerance and timing of heading. The correlation between spikelet fertility of individual panicles and both air temperature and panicle temperature during flowering was analyzed to compare tolerances among cultivars. The temperature (T₇₅) at which spikelet fertility was 75 % of maximum ranged from 34 to 39 °C air temperature and differed significantly among cultivars. Indica varieties had higher T₇₅ values than japonica varieties. The T₇₅ values based on panicle temperature also differed among cultivars, but the difference between indica and japonica varieties were less significant. We concluded that the higher temperature tolerances of indica cultivars in our experiments could be attributed to lower spikelet temperatures, and cultivars with similar spikelet temperatures still had different heat tolerances due to differences in pollination ability.

Salinity is one of the major factors limiting agricultural productivity in arid and semi-arid regions. Saline areas around the world are increasing and sources of fresh water are decreasing. The increasing importance of the use of brackish water to supplement regular irrigation has demonstrated a need for finding new potential plants with tolerance to irrigation with saline water which can be used in industrial agriculture. The aim of this study was to determine whether irrigation with brackish water of Crambe Abyssinica, a plant commonly used for industrial oil production and for ornamental purposes and with high economical value, especially in Central Asia and the Aral Sea region, is feasible. One more goal was to study how it influences growth and development, seed and oil yield and some physiological parameters such as photosynthesis, transpiration, chlorophyll content, osmotic potential and accumulation of fresh and dry weight. The effects of three salinity levels, 3, 6 and 9 dS m⁻¹, were investigated in a greenhouse experiment during two consecutive years. Results of this study showed that growth of Crambe abyssinica in arid zones and irrigation with mild saline water up to EC 6 dS m⁻¹, mostly common in these areas is feasible, suggesting tolerance to moderate salinity levels and feasibility of its culture in areas of the Aral Sea with adequate salinity levels. Consequently, in spite of the fact that biomass and seed yield were significantly decreased in plants irrigated with brackish water, Crambe abyssinica might be cultivated as an alternate source of green biomass and for industrial vegetable oil under conditions not suitable for conventional plant production.

Within the framework of climate change mitigation by sequestrating recalcitrant carbon in soil, biochar is considered as a promising soil amendment. Testing any such soil additives is vitally important, as they should not cause abiotic stress for plants due to chemical constituents they may contain. Thus, germination tests with spring barley (Hordeum vulgare) were conducted to assess phytotoxic effects of biochar, hydrochar and process-water from hydrothermal carbonization (HTC) as soil amendments. Additionally, single-component tests with substances found in process-waters were carried out with cress (Lepidium sativum). While biochars generally had no effect on germination, hydrochars and process-waters significantly inhibited germination. The dissolved organic carbon content predicted the germination-inhibiting effects observed. Three compounds resulted in partial (guaiacol) or total (levulinic acid and glycolic acid) inhibition of cress seed germination, and three others (acetic acid, glycolaldehyde dimer and catechol) had a negative impact on growth. Phytotoxic substances in chars appeared to be mostly water soluble and volatile. Pre-treatments of hydrochars and process-waters (i.e. storage and washing) were able to reduce germination inhibition. While phytotoxic substances that are generated during HTC stay in the products, biochars from kiln carbonization of the same feedstocks had no negative effects on germination, likely because volatiles evaporate during the conversion. Our study highlights the importance of comprehensively testing carbonized products for their compatibility with agricultural and horticultural systems.

This study illustrates the importance of randomization using two hypothetical field trials, one with a marked systematic trend and the other with a more erratic spatial pattern. The insights from these two examples are reinforced by analysis of a uniformity trial and a small simulation study. Results illustrate that both model-based spatial analysis and randomization-based analysis assuming independent errors are valid with full randomization but may be invalidated when randomization is lacking. It is concluded that randomization provides protection against different forms of spatial trend. The examples given in the study serve as a general reminder that agricultural experiments should be randomized whenever possible.

Abiotic stress can enhance the heterogeneity of fields, which leads to imprecise estimates of genotypic effects in variety trials. Our study is based on multilocation field trials of triticale (×Triticosecale Wittm.). Two of the six locations were affected by drought stress and showed increased field heterogeneity. At Willstätt, drought stress intensity was visually scored twice, and at Issoudun, overall impression of a plot was scored once. We investigated if the visual scorings can be used as covariates in an analysis of covariance (ancova) to eliminate the influence of different drought stress intensity on plot yields. For evaluation of the ancova models, we examined if the covariates were independent from the genotypic effects and linearly associated with grain yield. In addition, ancova models were compared with baseline and spatial models based on AIC and phenotypic correlation between genotype means estimated with the model under investigation in a drought stress location with genotype means calculated across the remaining locations. We found that both scorings in Willstätt fulfilled the requirements of an ancova and led to an increase in broad-sense heritability (h²) and efficiency. ancova with the second scoring increased h² from 0.03 for the baseline model to 0.60, whereas the best spatial model increased h² only up to 0.50. The scoring at Issoudun was not independent from the genotypic effects and reduced phenotypic correlations. We concluded that environmental factors causing spatially differing yield potential can be scored or measured and used as covariates to obtain more precise genotypic estimates.

This study analysed the alleviating effect of elevated CO₂ on stress-induced decreases in photosynthesis and changes in carbohydrate metabolism in two wheat cultivars (Triticum aestivum L.) of different origin. The plants were grown in ambient (400 μl l⁻¹) and elevated (800 μl l⁻¹) CO₂ with a day/night temperature of 15/10 °C. At the growth stages of tillering, booting and anthesis, the plants were subjected to heat stress of 40 °C for three continuous days. Photosynthetic parameters, maximum quantum efficiency of photosystem II (PSII) photochemistry (F_v/F_m) and contents of pigments and carbohydrates in leaves were analysed before and during the stress treatments as well as after 1 day of recovery. Heat stress reduced P_N and F_v/F_m in both wheat cultivars, but plants grown in elevated CO₂ maintained higher P_N and F_v/F_m in comparison with plants grown in ambient CO₂. Heat stress reduced leaf chlorophyll contents and increased leaf sucrose contents in both cultivars grown at ambient and elevated CO₂. The content of hexoses in the leaves increased mainly in the tolerant cultivar in response to the combination of elevated CO₂ and heat stress. The results show that heat stress tolerance in wheat is related to cultivar origin, the phenological stage of the plants and can be alleviated by elevated CO₂. This confirms the complex interrelation between environmental factors and genotypic traits that influence crop performance under various climatic stresses.

The development of low-water-input forages would be useful for improving the water-use efficiency of livestock production in semi-arid and arid regions. The desiccation-tolerant (DT) species Sporobolus stapfianus Gandoger and two desiccation-sensitive (DS) species, Sporobolus pyramidalis and Sporobolus fimbriatus (Trin.) Nees. (Poaceae), were evaluated for aerial biomass production and seed productivity under three different irrigation regimes. Sporobolus stapfianus displayed the least biomass production, whereas S. pyramidalis and S. fimbriatus produced up to 3.8- and 11.2-fold greater dry biomass, respectively, at the highest irrigation rate of 12 334 l (0.01 acre-feet). Sporobolus fimbriatus and to a lesser extent S. pyramidalis showed significant increases in biomass production in response to increased irrigation rates, whereas S. stapfianus did not. Sporobolus pyramidalis and S. fimbriatus exhibited 3.2- and 6.0-fold greater seed production, respectively, in response to increased irrigation rates, whereas S. stapfianus showed only a 1.4-fold increase. All Sporobolus species possessed forage quality traits (e.g. crude protein, fibre content) comparable to those of timothy, a forage grass grown widely in the Great Basin in the western United States. Micronutrient content exceeded the minimum requirements of beef cattle, without surpassing tolerable limits, with the exception of zinc, which appeared low in all three Sporobolus species. The low water requirements displayed by these species, combined with their acceptable forage qualities, indicate that these grasses have the potential to serve farmers and ranchers in semi-arid and arid regions of the western United States where irrigation resources are limited.

Predictions of extreme weather resulting from climate change will present huge challenges for scientists trying to maintain and increase agricultural production. A greater frequency of dry periods is predicted placing emphasis on the development of plant varieties that are able to maintain performance in dry conditions. The aim of this research was to determine the genetic variation for drought resistance among a large range of potential pasture or turf bermudagrasses (Cynodon spp.). Four hundred and sixty genotypes including ecotypes collected from different climatic zones of Australia, and commercial cultivars were established in the field and assessed during natural and imposed drought periods. Using descriptors of drought resistance such as turf quality and green cover, genotypes were classified into different groups; 436 genotypes were clustered into ten groups in one experiment, and 72 genotypes were clustered into three groups in a second. There was a high correlation of response (r = 0.78) for 47 genotypes common to both experiments suggesting that the drought resistance techniques used to group genotypes were robust. Physiological analyses of the genotypes within the superior drought resistance groups indicated that these group members were probably able to extract more available soil water during the drought period. No commercial cultivars were found in the most drought resistance groups. These field studies also suggested that future collections of bermudagrass ecotypes designed to select for drought resistance might best be carried out from regions that experience Mediterranean climates. The field evaluations presented here did not correlate well with drought resistance determined in previously reported shallow lysimeter (40 cm deep) experiments.

With world population expected to reach 9.2 billion people by 2050, improved irrigation methods will be needed to increase the productivity of agricultural land and improve food supply worldwide. The objective of this work was to examine the effect of regulated deficit irrigation (RDI) and alternate furrow irrigation (AFI) on the yield and yield components of two legume species (common bean and mungbean) produced as a second crop following winter wheat in Uzbekistan, Central Asia. Water relations and crop development were also examined. The research was conducted during two successive growing seasons in the Fergana valley. Production of mungbean using the severe stress RDI treatment in combination with AFI resulted in the highest yields with the lowest quantity of applied water in 2004. In addition, yields of common bean in the moderate stress treatment were not different from the recommended schedule, although irrigation events were decreased from 4 to 2. AFI did not reduce yields, and it did not interact with RDI to reduce yields further. In general, mungbean yields were higher than those of common bean. The combination of AFI and RDI can allow legume production with reduced water inputs.

Recent studies propose the combination of electrical energy and plant production, in which often only radiation peaks were used for energy production. Then, the effect on plant growth is assumed to be negligible. However, photosynthesis is known to be a monotonically increasing function of radiation. We studied the response of tomato to constraining the intensity of solar radiation. Tomato crops in greenhouse compartments were shaded when the outside photosynthetic photon flux density (PPFD) exceeded 640 and 1280 μmol m⁻² s⁻¹, resulting in a 57 % and 34 % reduction in the PPFD integral over the growing period compared to the non-shaded control. Constraining the intensity of solar radiation significantly reduced photosynthesis, growth and yield of tomato plants. Model-derived estimates of reduction in crop dry matter increment were 50 % and 28 % for the strongly and moderately PPFD constrained crops. However, measured plant dry matter increment decreased only by 31 % and 19 %, respectively, that is, light use efficiency increased markedly. This indicates a strong adaptation of the plant's metabolism to cope with the limitation in light availability such as increasing the specific leaf area and reducing respiration. Surprisingly, this was only of little concern to the fruit quality, because no effect of constraining PPFD on the concentration of total dry matter, sugars and lycopene in the fruits could be observed. The concentration of titratable acids was significantly increased, however, when constraining PPFD, while ß-carotene was slightly decreased. When combining plant and energy production, yield reductions in systems that reduce the supply of solar radiation to crops only at high irradiances will be less considerable than in systems that permanently shade the crop. However, yield losses in tomato production remain significant in both system types.

Our study was conducted to determine agronomic optimum seeding rates (AOSR) for irrigated maize under a range of agroecological conditions in Texas. Environmental factors that affect irrigated maize production vary considerably across Texas. This variability imposes region-specific limitations on statewide maize seeding rate recommendations. Our research examined the efficiency of varying seeding rates on irrigated maize grain yields in five USEPA Level IV Ecoregions that comprise most of the irrigated maize-producing area of Texas. The selected sites span a distance of 1200 km from south to north Texas and elevations from 20 to 1218 m above mean sea level. We conducted the study over three growing seasons from 2005 through 2007 in two Level IV Ecoregions of the High Plains of North Texas (N), one in the East Central Plains (E), one in the Southern Plains and one in Western Gulf Coastal Plains of South Texas (S). We observed that maximum grain yields and AOSR to achieve maximum maize grain yields vary considerably among ecoregions. In South Texas, we observed grain yield response rates of 125–129, 151 kg 1000 seeds⁻¹ in E and 163–199 kg 1000 seeds⁻¹ in N. We show that growing season average daily minimum air temperature (T_MIN) explains most of this variation (r² = 0.98, P-value < 0.01) and conclude that seeding rate efficiency is concomitant to T_MIN. Maximum grain yields (GY_MAX) determined with seeding rate response analysis also varied among ecoregions and with T_MIN from south to north Texas, from a low of 8.3 Mg ha⁻¹ in S to a high of 18.4 Mg ha⁻¹ in N (r² = 0.59, P-value < 0.01). We conclude that development of agronomic management models by Level IV Ecoregions of Texas combined with site-specific T_MIN climatological data serve as a valid template for delivering robust and agroecozone-specific irrigated maize seeding rate recommendations in Texas.

The adverse effects of tropospheric ozone (O₃) on crop photosynthesis, growth and yield have been documented in numerous studies over the last decades, but little information from field experimentation exists on how modern European winter wheat cultivars respond to O₃. Two winter wheat cultivars (Astron and Pegassos) differing in development characteristics were exposed to non-filtered ambient air or non-filtered air plus 30 ppb and non-filtered air plus 60 ppb O₃ (8 h day⁻¹) in open-top field chambers. At several dates during growth, green leaf area was determined by destructive harvests. Leaf gas exchange, pigment content and xanthophyll cycle activity, and photochemical efficiency by chlorophyll a fluorescence were measured. O₃ exposure induced accelerated senescence with no difference between cultivars. Photosynthesis declined especially in Pegassos; however, stomatal conductance was hardly affected by O₃. Pigment contents were reduced by O₃ exposure, and de-epoxidation index increased. Photochemical efficiency (F_v/F_m) declined, whereas actual quantum yield (Φ_PSII) did not respond to O₃. O₃ exposure reduced grain yield in both cultivars. However, yield of Pegassos was more affected by O₃ exposure than yield of Astron, suggesting a higher O₃ sensitivity of Pegassos. The data presented in this manuscript indicate a need to test whether high-yield varieties such as Pegassos are particularly sensitive to O₃ exposure.

Sorghum [(Sorghum bicolor L.) Moench] is a highly productive crop plant, which can be used for alternative energy resource, human food, livestock feed or industrial purposes. The biomass of sorghum can be utilized as solid fuel via thermochemical routes or as a carbohydrate substrate via fermentation processes. The plant has a great adaptation potential to drought, high salinity and high temperature, which are important characteristics of genotypes growing in extreme environments. However, the climate change in the 21st century may bring about new challenges in the cultivated areas. In this review, we summarize the most recent literature about the responses of sorghum to the most important abiotic stresses: nutrient deficiency, aluminium stress, drought, high salinity, waterlogging or temperature stress the plants have to cope with during cultivation. The advanced molecular and system biological tools provide new opportunities for breeders to select stress-tolerant and high-yielding cultivars.

Quinoa is a native Andean crop for domestic consumption and market sale, widely investigated due to its nutritional composition and gluten-free seeds. Leaf water potential (Ψ_leaf) and its components and stomatal conductance (g_s) of quinoa, cultivar Titicaca, were investigated in Southern Italy, in field trials (2009 and 2010). This alternative crop was subjected to irrigation treatments, with the restitution of 100 %, 50 % and 25 % of the water necessary to replenish field capacity, with well water (100 W, 50 W, 25 W) and saline water (100 WS, 50 WS, 25 WS) with an electrical conductivity (EC_w) of 22 dS m⁻¹. As water and salt stress developed and Ψ_leaf decreased, the leaf osmotic potential (Ψ_π) declined (below −2.05 MPa) to maintain turgor. Stomatal conductance decreased with the reduction in Ψ_leaf (with a steep drop at Ψ_leaf between −0.8 and 1.2 MPa) and Ψ_π (with a steep drop at Ψ_π between −1.2 and −1.4 MPa). Salt and drought stress, in both years, did not affect markedly the relationship between water potential components, RWC and g_s. Leaf water potentials and g_s were inversely related to water limitation and soil salinity experimentally imposed, showing exponential (Ψ_leaf and turgor pressure, Ψ_p, vs. g_s) or linear (Ψ_leaf and Ψ_p vs. SWC) functions. At the end of the experiment, salt-irrigated plants showed a severe drop in Ψ_leaf (below −2 MPa), resulting in stomatal closure through interactive effects of soil water availability and salt excess to control the loss of turgor in leaves. The effects of salinity and drought resulted in strict dependencies between RWC and water potential components, showing that regulating cellular water deficit and volume is a powerful mechanism for conserving cellular hydration under stress, resulting in osmotic adjustment at turgor loss. The extent of osmotic adjustment associated with drought was not reflected in Ψ_π at full turgor. As soil was drying, the association between Ψ_leaf and SWC reflected the ability of quinoa to explore soil volume to continue extracting available water from the soil. However, leaf ABA content did not vary under concomitant salinity and drought stress conditions in 2009, while differing between 100 W and 100 WS in 2010. Quinoa showed good resistance to water and salt stress through stomatal responses and osmotic adjustments that played a role in the maintenance of a leaf turgor favourable to plant growth and preserved crop yield in cropping systems similar to those of Southern Italy.

Combined effects of temperature and light quality on plants have received little attention. We investigated the single and interactive effects of temperature and light quality on growth and physiological characteristics of four canola (Brassica napus) cultivars – Clearfield 46A76 (cv₁), Clearfield 45H72 (cv₂), Roundup Ready 45H24 (cv₃) and Roundup Ready 45H21 (cv₄). Plants were grown under lower (24°/20 °C) and higher (30°/26 °C) temperature regimes at low red/far-red (R/FR), normal R/FR and high R/FR light ratios in environment-controlled growth chambers (16 h light/8 h dark). Higher temperature reduced stem height and diameter; leaf number and area; dry matter of all plant parts; and specific leaf weight, but increased leaf area ratio; and chlorophyll (Chl) fluorescence (Y). Low R/FR increased stem height; Y; and ethylene, but decreased stem diameter; F_v/F_m; Chl a; Chl b; and carotenoids. Among cultivars, plants from cv₄ were tallest with thickest stems and greatest dry matter. None of the main factors affected gas exchange. Higher temperature at high R/FR caused cv₃ to be shortest, whereas lower temperature at low R/FR caused cv₄ to be tallest. We conclude that heat and other stress factors will adversely affect sensitive crops, but tolerant genotypes should perform well under future climate.

Maize (Zea mays L.) yield is often restricted by low soil water availability, particularly late in the growing season. To increase yields, genetic options for more effective use of available soil water are being explored. One option is to select genotypes that have restricted transpiration rate under high vapour pressure deficit (VPD) conditions so that soil water is conserved for use later in the growing season. While genetic variation for this trait has been identified within several crop species, such variation has never been explored in maize. The objective of this study was to examine transpiration rate of 35 single-cross hybrids to determine whether hybrids can be identified that express limited transpiration under high VPD. Two sets of experiments were undertaken in which plants were exposed to a range of VPD in chambers. A two-phase transpiration response was observed in 11 hybrids in which there was a threshold VPD above which transpiration rate was restricted. The VPD threshold varied from 1.7 to 2.5 kPa among these hybrids. Eight hybrids were included in both sets of experiments, and the same results were obtained in both experiments, indicating that expression of the trait was consistent.

Salinity primarily affects plants by inhibiting shoot growth. Salt-sensitive plants have been suggested to accumulate Na⁺ within their leaf apoplast under salinity, leading to a reduced water status. Evidence related to apoplastic Na⁺ accumulation is still enigmatic. We have focused on the effect of a short-term salt treatment by using the salt-sensitive Vicia faba. Moreover, we have examined the role of silicon in alleviating sodium accumulation in the apoplast. Salt-sensitive field beans have been subjected to increasing levels of salinity, with and without the addition of silicon under hydroponic conditions. We have demonstrated that the dicot Vicia faba exhibits a rise in Na⁺ concentration in the leaf apoplast at higher salinity levels; this is significantly ameliorated by the addition of silicon. Further, enhanced shoot growth under high salt treatment in the presence of added silicon is correlated with a significant decrease in Na⁺ concentration in the leaves. The novelty of the current study is the detection of a high Na⁺ concentration in the leaf apoplast of the salt-sensitive dicot field bean. Our results support Oertli's hypothesis that extracellular salt accumulation can lead to wilting leaves, plant growth reduction and cell death.

High temperature (HT) stress is one of the major environmental factors influencing yield of soybean (Glycine max L. Merr.) in the semi-arid regions. Experiments were conducted in controlled environments to study the effects of HT stress on anatomical changes of pollen and their relationship to pollen function in soybean genotype K 03-2897. Objectives of this study were to (a) quantify the effect of HT stress during flowering on pollen function and pod set and (b) observe the anatomical changes in pollen grains of soybean plants grown under HT stress. Plants were exposed to HT (38/28 °C) or optimum temperature (OT, 28/18 °C) for 14 days at flowering stage. HT stress significantly decreased in vitro pollen germination by 22.7 % compared to OT. Pollen from HT stress was deformed; it had a thicker exine wall and a disintegrated tapetum layer. HT stress decreased pod set percentage (35.2 %) compared to OT. This study showed that decreases in pollen in vitro germination by HT stress were caused by anatomical changes in pollen, leading to decreased pod set percentage under HT stress.

High temperatures during rice grain ripening reduced yield and grain quality. The proportion of milky white grains was 43.6 % at 30 °C but only 6.5 % at 25 °C. Grain filling was initially faster at 30 °C and finished earlier, and the final dry matter content was less, than at 25 °C. High temperature strongly suppressed the expression of the sucrose transporter gene OsSUT1 and starch synthesis-related genes SuSy2, AGPS2b, BEIIb and Granule-bound starch synthase in grains during early grain filling; the transcription levels of OsSUT1 at 14 days after flowering (DAF) were about 60 % lower in grains, flag leaf blade, flag leaf sheath and first leaf sheath. These facts are possibly involved in the earlier termination of grain filling at 21 DAF, following the rapid rise of grain dry weight from 0 to 7 DAF, due to possible reduction in assimilate supply via OsSUT1 under the high temperature. When panicles were partly clipped, the resultant increase in assimilate supply to the remaining grains significantly upregulated the expression of OsSUT1 and the starch synthesis-related genes at 14 DAF, which consequently accelerated starch accumulation in the grains and ultimately increased the grain weight of remaining grains at 30 °C. These results indicate that high temperature during grain filling reduces grain yield and quality by changing the expression of OsSUT1 and starch synthase-related genes, resulting in earlier ripening due to hastened or premature assimilate supply to grains.

In this study, the impacts of climate variables on the mean and variability in Aus variety rice yield in Bangladesh are assessed. Using the theoretical framework of the Just–Pope production function, cross-sectional time series data on Aus rice yield and maximum temperature, minimum temperature and rainfall at a district level over a period of 38 years are analysed for evidence of rice yield variability as a result of climate change. The findings reveal that minimum temperature and rainfall decrease Aus yield variability. However, maximum temperature appears to increase variability, which may reduce Aus rice production. Therefore, government should create an enabling environment to develop temperature-tolerant rice varieties for Aus rice crop to ensure ongoing food security.

Plants at various stages of growth are differentiated in their susceptibility to environmental stresses and possibility of regeneration during recovery period after cessation of stress. The role of antioxidative enzymes in the stabilisation of the physiological state of field bean plants was studied. Catalase, peroxidises activity, and hydrogen peroxide accumulation were determined after 1 and 7 days of flooding and after 1 and 7 days of recovery from flooding. The influence of flooding on plants growth was analysed on the basis of leaf area index (LAI), relative growth rate (RGR) and net assimilation rate (NAR). Changes in antioxidative enzymes caused by flooding applied at vegetative stage were reversible. In generative plants, antioxidative enzymes were activated to a greater extent during recovery period and in contrast to vegetative plants did not attain the control level after that period. The reduction in growth was greater when flooding stress was applied at vegetative stage. Vegetative plants regardless of the stabilisation of antioxidant system were not able to restore the physiological function to attain the optimal growth level after flooding. Probably other injuries caused by flooding had a dominant effect on enzymatic antioxidant changes during stress period.

Two chilling-tolerant genotypes, that is, weedy rice WR03-45 and cultivated rice Lijiangxintuanheigu and two chilling-sensitive genotypes, that is, weedy rice WR03-26 and cultivated rice Xiuzinuo were used in this study to investigate the effects of exogenous abscisic acid (ABA) on protection against chilling damage as well as on changes in physiological features. The results showed that under chilling stress the increased levels of superoxide radical (), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) in WR03-45 and Lijiangxintuanheigu were lower than those in WR03-26 and Xiuzinuo. Activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR)) and non-enzymatic antioxidants (ascorbate acid (AsA) and reduced glutathione (GSH)) were enhanced in WR03-45 and Lijiangxintuanheigu, whereas they were decreased significantly in WR03-26 and Xiuzinuo. Application of exogenous ABA reduced the chilling damage in the four genotypes. The pre-treatment with ABA decreased the levels of , H₂O₂ and MDA caused by chilling stress in the four genotypes through increasing the activities of SOD, CAT, APX, GR and the contents of AsA and GSH in the four genotypes under chilling stress. Moreover, pre-treatment with Fluridone, the ABA biosynthesis inhibitor, prohibited the effects of ABA through enhancing the oxidative damages and suppressing the antioxidant defence systems under chilling stress. The results indicate the mechanism for rice with chilling tolerance is to enhance the capacity of antioxidant defence systems under chilling stress. Furthermore, ABA plays important roles in the tolerance of rice against chilling stress for it could induce the capacity of whole antioxidant defence systems including enzymatic and non-enzymatic constitutions under chilling stress.

Root activity plays a dominant role in grain filling in cereal crops. However, the importance of deep roots for regulating post-anthesis leaf senescence is not clearly understood in wheat (Triticum aestivum L.). In this study, we used ³²P tracing to estimate the difference in wheat root activity at soil depths of 30 and 70 cm and the root restriction method to investigate the effects of vertical distribution of deep roots on leaf senescence, with non-restricted plants as controls. Recovery of radioactive ³²P indicated that deep roots had significantly higher activity than upper roots in wheat. Root restriction at a soil depth of 50 cm caused significant decreases in the activities of superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6) and ascorbate peroxidase (EC 1.11.1.11) at 16 days after anthesis and thereafter resulting in an increase in malondialdehyde. As a result, chlorophyll levels and net photosynthesis decreased. Ultimately, the root-restricted wheat produced a significantly lower grain yield than the non-restricted controls. These data suggest that deep roots are pivotal for regulating plant senescence, duration of grain filling, and yield formation.

In every agroforestry system, the tree canopy reduces the incident radiation for the crop. However, cereal varieties were selected, and most crop growth models were designed for unshaded conditions, so both may be unsuited to agroforestry conditions and performance. In southern France, durum wheat productivity was monitored over 2 years in an agroforestry system including walnut trees and under artificial shade conditions. Yield components were measured in both full and reduced light conditions. The cereal yield was always decreased by shade; by almost 50% for the heaviest shade conditions (31% of light reduction). The main effect of the shade was the reduction in the number of grains per spike (35% at the most) and in the weight of grains (16% at the most). The mean grain weight was moderately affected, while the protein content was increased in shaded conditions (by up to 38% for artificial shade). Consequently, the protein yield per hectare was less reduced by the shade than the dry matter grain yield. A crop model (STICS) was also used to simulate the crop productivity in full light and shaded conditions, but the crop LAI and the yield components were not correctly simulated in the shade. The simulations emphasized the sensitivity of the wheat grain filling to shade during the critical period, 30 days before flowering, for yield elaboration. Further experimental and modelling studies should take into account the heterogeneity of shade intensity due to the shape of the tree crown, the width of the crop alley and the orientation of the tree rows and the modification of carbon allocation inside the plant.