Simulation of future global warming scenarios in rice paddies with an open-field warming facility

To simulate expected future global warming, hexagonal arrays of infrared heaters have previously been used to warm open-field canopies of upland crops such as wheat. Through the use of concrete-anchored posts, improved software, overhead wires, extensive grounding, and monitoring with a thermal camera, the technology was safely and reliably extended to paddy rice fields. The system maintained canopy temperature increases within 0.5°C of daytime and nighttime set-point differences of 1.3 and 2.7°C 67% of the time

Auxin and Cytokinin Interplay during Leaf Morphogenesis and Phyllotaxy

Auxins (IAA) and cytokinins (CKs) are the most influential phytohormones, having multifaceted roles in plants. They are key regulators of plant growth and developmental processes. Additionally, their interplay exerts tight control on plant development and differentiation. Although several reviews have been published detailing the auxin-cytokinin interplay in controlling root growth and differentiation, their roles in the shoot, particularly in leaf morphogenesis are largely unexplored. Recent reports have provided new insights on the roles of these two hormones and their interplay on leaf growth and development. In this review, we focus on the effect of auxins, CKs, and their interactions in regulating leaf morphogenesis. Additionally, the regulatory effects of the auxins and CKs interplay on the phyllotaxy of plants are discussed

Non-destructive assessment of plant nitrogen parameters using leaf chlorophyll measurements in rice

Non-destructive assessment of plant nitrogen (N) status is essential for efficient crop production and N management in intensive rice (Oryza sativa L.) cropping systems. Chlorophyll meter (SPAD-502) has been widely used as a rapid, non-destructive and cost-effective diagnostic tool for in-season assessment of crop N status. The present study was intended to establish the quantitative relationships between chlorophyll meters readings, plant N concentration (PNC), N nutrition index (NNI), accumulated N deficit (AND), and N requirement (NR), as well as to compare the stability of these relationships at different vegetative growth stages in Japonica and Indica rice cultivars. Seven multi-locational field experiments using varied N rates and seven rice cultivars were conducted in east China. The results showed that the PNC and chlorophyll meters readings increased with increasing N application rates across the cultivars, growing seasons, and sites. The PNC and chlorophyll meters readings under varied N rates ranged from 2.29 to 3.21, 1.06 to 1.82 and 37.10 to 45.4 and 37.30 to 46.6, respectively, at TL and HD stages for Japonica rice cultivars, while they ranged from 2.25 to 3.23, 1.34 to 1.91 and 35.6 to 43.3 and 37.3 to 45.5 for Indica rice cultivars, respectively. The quantitative relationships between chlorophyll meters readings, PNC, NNI, AND, and NR established at different crop growth stages in two rice ecotypes, were highly significant with R2 values ranging from 0.69 to 0.93 and 0.71 to 0.86 for Japonica and Indica rice, respectively. The strongest relationships were observed for AND and NR at panicle initiation and booting stages in both rice ecotypes. The validation of the relationships developed in the present study with an independent data exhibited a solid model performance and confirmed their robustness as a reliable and rapid diagnostic tool for in-season estimation of plant N parameters for sustainable N management in rice. The results of this study will offer a suitable approach for managing N application precisely during the growth period of the rice crop in intensive rice cropping systems in east China

Efficacy, Energy Budgeting, and Carbon Footprints of Weed Management in Blackgram (<i>Vigna mungo</i> L.)

Weed management in blackgram is one of the most efficient ways to improve its yield, as uncontrolled weed growth causes a significant decrease in crop yield. A field experiment was performed at Berthin, Himachal Pradesh, India, to investigate the efficacy, energy use efficiency (EUE), and carbon footprints of weed management tactics. Twelve weed control treatments were tested applied alone or in combination at pre and post emergence stages. The most prominent weeds were Cyperus iria, Dactyloctenium aegyptium, and Echinochloa colona, which caused a 68.1% loss in unweeded conditions. The application of weed control treatments reduced the weed count at 60 DAS from around 50% to 90%. The most efficient weed control treatment was pre-emergence (PRE) use of ready mix imazethapyr 35% + imazamox 35% WG @ 80 g ha−1, which resulted in a minimum weed infestation (i.e., weed count and weed biomass) and consequently highest yield. Its efficacy in weed control treatment was on par with PRE use of ready mix imazethapyr (35%) + imazamox (35% WG @ 70 g ha−1. Maximum energy use efficiency was also obtained upon PRE use of imazethapyr (35%) + imazamox (35% WG) @ 80 g ha−1 (8.27), trailed by PRE use of imazethapyr + imazamox @ 70 g ha−1 (7.84), mainly because of the higher yield obtained in these treatments which shows their efficiency in energy conversion. The carbon footprints were observed to be the lowest in ready mix combination of imazethapyr (35%) + imazamox (35% WG) applied at 80 g ha−1 (0.11 kg CE kg−1 yield), followed by imazethapyr (35%) + imazamox (35% WG) applied at 70 g ha−1 (0.12 kg CE kg−1 yield), as it resulted in the lowest emission per unit output production

Comparative Physiological, Biochemical, and Proteomic Responses of Photooxidation-Prone Rice Mutant 812HS under High Light Conditions

Photosynthetic efficiency decreases as light energy surpasses the photosynthesis capacity. This study was designed to investigate the potential effects of high-intensity light on the photooxidation-prone mutant 812HS of rice and its wild-type 812S during yellow and recovering stages. Results showed that in the yellowing stage, light oxidation occurs due to the exposure of mutant 812HS leaves to the high sunlight, which causes yellowing of the leaves, leading to a reduction in the photochemical activities, physiological mechanisms, and protein contents in mutant 812HS. In the recovery stage, mutant 812HS leaves were exposed to the maximum high brightness, the mutant’s leaves were draped with a dark cover to decrease the exposure of leaves of the plants from direct sunlight, which leads to the restoration of the green color again to the mutant 812HS leaves, leading to improving the performance of the photochemical activities, physiological mechanisms, and protein contents in mutant 812HS. Exposing leaves of mutant 812HS to high light at the yellow stage also resulted in a decrease in the net photosynthetic rate (Pn) in carotenoids content and chlorophyll a and b. Similarly, chlorophyll fluorescence of mutant 812HS decreased in (O-I-J-I-P) curves, and the ATP content, Mg2+-ATPase, and Ca2+-ATPase activities also decreased. An increase in energy dissipation was observed, while ABS/RC, DI0/RC, and TR0/RC values in mutant 812HS at the yellow stage increased. During photooxidation, an increase in O2•– and H2O2 contents was observed in mutant 812HS. While O2•– and H2O2 contents were decreased in mutant 812HS at the recovery stage. The rate of thylakoid membrane protein content was significantly decreased in mutant 812HS at the yellow stage, while at the recovery stage, there was no significant decrease. Our findings showed that photooxidation prompted oxidative damages and lipid peroxidation that caused severe damages to the membranes of the cell, photosynthetic pigments degradation, protein levels, and photosynthesis inhibition in mutant 812HS

Role of pollination in yield and physicochemical properties of tomatoes (Lycopersicon esculentum)

Very little is known about pollination and its effects on the yield and physicochemical properties of flowering plants in tropical countries. Wind and insect pollinators are among our natural resources because pollination is the most important ecosystem service performed by wind and insects, and is vital to the socio-economic status of human beings. In this experiment, different pollination methods for tomato plants were examined. Self-pollination was encouraged by covering the plants with a plastic sheet. Wind and insects were excluded from these plants, and thus only self-pollination was possible. The experiment occurred during the flowering stage. Wind-pollinated plants were covered with a muslin cloth, which excluded insects, and only wind could pass through the cloth. For insect pollination, plants remained uncovered, allowing free access to insects to pollinate the flowers. At fruit maturity, when fruits were completely red, fruits from each treatment were harvested on the same date and under the same conditions. Results illustrated the substantial importance of insects as pollinators of tomato crops. Open field had greater tomato yield and positive effects on physicochemical properties on fruit than under self and wind pollination. Keywords: Pollination methods, Tomato, Lycopersicon esculentum, Physicochemical properties, Yiel

Foliar Application of Potassium Mitigates Salinity Stress Conditions in Spinach (<i>Spinacia oleracea</i> L.) through Reducing NaCl Toxicity and Enhancing the Activity of Antioxidant Enzymes

Agronomic biofortification is the purposeful utilization of mineral fertilizers to increase the concentration of desired minerals in edible plant parts for enhancing their dietary intake. It is becoming crucial to enhance the dietary intake of K for addressing hidden hunger and related health issues such as cardiac diseases and hypertension. This study was designed to enhance the potassium concentration in edible parts of spinach through its foliar application under saline environment. The salinity levels of electrical conductivity (EC) = 4, 6, and 8 dS m−1 were applied using sodium chloride (NaCl) along with control. The levels of K for foliar sprays were 5 and 10 mM, along with control. The present experiment was performed under two factorial arrangements in a completely randomized design (CRD). After 60 days of sowing, the crop was harvested. Data regarding growth, ionic, physiological, and biochemical parameters, i.e., shoot dry weight, relative water content, electrolyte leakage, total chlorophyll content, tissue sodium (Na) and K concentration, activities of superoxide dismutase (SOD), and catalase (CAT) were recorded and those were found to be significantly (p ≤ 0.05) affected by foliar application of K on spinach under saline conditions. The highest growth, physiological and biochemical responses of spinach were observed in response to foliar-applied K at 10 mM. It is concluded that agronomic bio-fortification by foliar use of K can be a useful strategy to increase tissue K intakes and minimize Na toxicity in the vegetables studied under saline conditions

Effects of different tillage and residue management systems on soil organic carbon stock and grain yield of rice–wheat double cropping system

Of late, intensive agricultural practices are often associated with many negative implications for soil systems, such as decline in soil organic matter and biological diversity, and increase in the risk of soil erosion, and degradation of soil physical quality. However, conservation agriculture (CA) offers minimum soil disturbance, improving and creating more efficient use of natural resources, enhancing use efficiency of external inputs and increasing soil functioning, organic matter content, and biodiversity. However, CA practices need to be redefined at the specific field level or growing conditions to promote sustainable production system without deteriorating soil health, and to manage profitability. Therefore, a fixed-site field experiment was conducted to evaluate the effects of different tillage and residue management practices; CT0 (puddled transplanted rice followed by conventional tilled wheat sown with residue removal); CTR (puddled transplanted rice followed by conventional tilled wheat sown with residue retention); NT0 (direct seeded rice followed by zero-tilled wheat sown with residue removal); NTR (direct seeded rice followed by zero-tilled wheat sown with residue retention) on soil organic carbon (SOC) stock and grain yield of rice–wheat double cropping system. The results showed that the mean SOC stock increased by 31%, 21.9% and 15.3% and by 35.2%, 22% and 17% under NTR, CTR, and NT0 compared with CT0. Furthermore, the SOC sequestration rate in NTR was significantly higher than other treatments. Particulate organic carbon (POC) concentration was 58.4% higher in 0–15 cm than 15–30 cm soil layer, and the maximum concentration was recorded under NTR and minimum was under CT0. The highest average rice grain yield was recorded under CTR, which was 5.5%, 16.2% and 24.3% higher than CT0, NTR and NT0, respectively. Both NTR and CTR produced more average wheat yield, which was 8.4% and 8.5% higher than CT0 and NT0, respectively. Principal component analysis (PCA) also showed that cumulative cropping system yield and SOC were increased under CTR, NTR as compared to other treatments. Therefore, it can be drawn that residue retention could be a useful management practice to increase SOC stock and grain yield under both tillage practices in the rice–wheat cropping system

Effects of Soil Moisture Content on Germination and Physiological Characteristics of Rice Seeds with Different Specific Gravity

Soil relative water content and seed plumpness have been shown to be the key factors affecting seed germination and seedling growth of rice under direct drought cropping. It remains to be determined whether seed germination and seedling growth of water-saving and drought-resistant rice (WDR) and conventional rice with the same proportion of rice seed have the same response to soil moisture changes. The purpose of this study was to investigate the seed germination and physiological characteristics of the rice cultivars Guangliangyou 1813 (GLY-1813,indica hybrid rice) and Hanyou 73 ((HY-73), WDR) with four different specific gravities (T1, T2, T3, and T4; the rice seeds were divided into four specific gravity levels by weight using saline water, the representative specific gravities were 1.2 kg m−3, respectively), at five soil moisture content gradients (soil relative water contents of 10–20%, 20–40%, 40–60%, 60–80%, and 80–100%), under dry direct seeding conditions. The results showed that GLY-1813 had a higher germination potential, germination and seedling emergence rates, greater root dry weight, seedling dry weight, root oxidation activity, and chlorophyll content, and lower malondialdehyde (MDA) content when the soil relative water content was 20–40% or 40–60%. Cultivar HY-73 had the highest germination rate and seedling physiological activity at 20–40% relative water content; its growth vigor was better than that of GLY-1813 at the same soil moisture level. In conclusion, the soil relative water content for seed germination of HY-73 was 20–40%, which was less than that of GLY-1813. When soil relative water content was sufficient for seed germination and growth, the higher the plumpness of the rice seed, the easier it was to resist the negative effects of an adverse growth environment

Radiation efficiency and nitrogen fertilizer impacts on sunflower crop in contrasting environments of Punjab, Pakistan

Sunflower (Helianthus annuus L.) is the leading non-conventional oilseed crop in Pakistan. Nitrogen fertilizer can affect plant growth and productivity by changing canopy size which has an effect on the radiation use efficiency (RUE) of the crop. The response of sunflower hybrids in terms of phenology, fraction of intercepted radiation (F-i), and RUE to nitrogenous rates (0, 60, 120, 180, and 240 kg ha(-1)) was studied in three field experiments conducted in three various environments: Multan (arid), Faisalabad (semi-arid), and Gujranwala (sub-humid) during spring seasons 2008 and 2009. The treatments were laid out according to a randomized complete block design with split plot arrangements, keeping the sunflower hybrids in main plots and nitrogen rates in subplots, and replicated three times. The results showed Hysun-38 took a maximum number of days to anthesis (101) as compared to Pioneer-64A93 (100) and Hysun-33 (99). The mean values of F-i were 0.850, 0.903, and 0.978, and the estimated values of RUE for total aboveground dry matter were 2.14, 2.47, and 2.65 g MJ(-1) at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The values of RUE for grain yield (RUEGY) were 0.78, 0.98, and 1.26 g MJ(-1) at experimental locations of Multan, Faisalabad, and Gujranwala, respectively. The average RUEGY values over three locations were 2.61, 2.60, 2.43, and 2.36 g MJ(-2) in N-4 (180 kg ha(-1)), N-5 (240 kg ha(-1)), N-3 (120 kg ha(-1)), and N-2 (60 kg ha-1) treatments, respectively. Increasing rates of N increased RUEGY over the standard treatment N-3 (120 kg N ha(-1)); however, the averaged values over three locations were 1.22, 1.08, 0.99, and 0.92 g MJ(-2) in N-4, N-5, N-3, and N-2 treatments, respectively. Therefore, optimum water and N doses are important for attaining higher RUE, which may enhance sunflower growth and yield