Pre-flowering Stage Research Articles

Silicon Supplementation Improves Tolerance to Water Deficiency in Sorghum Plants by Increasing Root System Growth and Improving Photosynthesis

This study was conducted to assess the effects of silicon treatments on architecture and morphometry of root systems of sorghum plants grown at two different soil water levels and to elucidate whether physiological improvements caused by silicon were related to morphometric modifications of the root system. Plants of the sorghum genotype BRS332 which is sensitive to drought at pre-flowering stage were used in this study. These plants were grown in a greenhouse, either at field capacity or under water deficiency, and were treated with silicon or were untreated. Leaf water potential was evaluated at noon, and gas exchange, photosynthetic pigment levels, relative aquaporin expression, root system morphometry, and grain yield were assessed. Silicon treatments mitigated the effects of water deficiency on leaf potential, photosynthesis, instantaneous carboxylation efficiency, and morphometry of the root system. These positive effects contributed to a higher grain yield, and thus indicated higher tolerance to drought. The beneficial effects of silicon also occurred in plants grown at field capacity. Silicon treatments did not increase the relative expression of aquaporin genes. However, we observed that expression of aquaporin TIP4 responded more strongly to drought than that of aquaporins PIP1;6 and PIP1;3/1;4. We conclude that silicon supplementation increases the tolerance of sorghum plants to drought by increasing growth of the root system and mitigating adverse effects of drought on photosynthesis.

Understanding boosting selenium accumulation in Wheat (Triticum aestivum L.) following foliar selenium application at different stages, forms, and doses.

There are a lack of systematic studies comparing the effects of foliar-applied selenium (Se) with different Se sources at different growth stages in wheat. Herein, we biofortified wheat via the foliar application of selenite and selenate at different rates and different stages under field conditions. Results showed that foliar-applied selenate and selenite had no significant effect either on wheat biomass or grain yield (p < 0.05). Selenium distribution in different parts of wheat plant ranked decrease as leaf > root > grain > glume > stem with selenite treatment, and it appeared in the decline order as leaf > grain > glume > stem > root with selenate treatment. These results suggested that biofortification with selenate caused, relatively to selenite, a higher accumulation of Se in grains. Foliar application of Se of either selenate or selenite at pre-filling stage was superior in improving the Se concentration of wheat grains than application at pre-flowering stage. Meanwhile, organic Se comprised about 72-93% of total Se in wheat grains, which was reduced by 5.8% at high Se rate (100 g ha-1), irrespective of the forms of Se or stages applied. The organic Se proportion in wheat grains was 9% higher with the selenate treatment than with the selenite treatment. Selenomethionine (SeMet) was the main organic species (67-86%) in wheat grains, followed by selenocysteine (SeCys2). In summary, our results indicate that Se biofortification of wheat is most effective with 20 g ha-1 selenate foliar-applied at pre-filling stage.

Quinic acid derivatives from Artemisia annua L. leaves; biological activities and seasonal variation

Genus Artemisia is widely known to have various therapeutic applications and chemical constituents. A. annua L. (commonly known as sweet wormwood or Qinghao) is an annual herb native to China, traditionally used for treating fever and malaria, and as a source of artemisinin. In the present study, a bio-guided fractionation of the 70% ethanolic extract of the leaves of A. annua cultivated in Egypt produced a bioactive polar fraction. Daily doses of this fraction (100 mg/kg b.wt) for 4 weeks substantially reduced the level of the CCl4-mediated increase in the liver enzymes; AST, ALT and ALP. Similarly, daily doses of the polar fraction (100 mg/kg) significantly reduced the blood glucose level in alloxan-induced diabetic by 32.1% in the second week and 46.9% in the fourth week, relative to that demonstrated by metformin (66.2%), and significantly (p < 0.01) restored to normal the blood glutathione level (35.2 ± 1.3 mg/dL), almost identical to that shown by vitamin E. Further purification of the bioactive fraction led to the isolation of 5 quinic acid derivatives; 3-feruloylquinic acid, 3,5-dicaffoeylquinic acid, 4,5-dicaffoeylquinic acid, 3,4-dicaffoeylquinic acid, and 3,4-dicaffoeylquinic acid methyl ester. The isolated compounds are reported here for the first time in A. annua, leaves cultivated in Egypt and suggested to be responsible, at least in part, to the biological activities of the polar fraction. Seasonal variation in the content of quinic acid derivatives in the leaves of A. annua L. was investigated during four harvest seasons (March, May, July "pre-flowering stage" and August-September "flowering stage") using RP-HPLC. The content of 3-feruloylquinic acid varied greatly throughout the year. It was found to be the lowest (0.036% w/w) in March "leaf stage" but increased through the warmer months from May to June (0.61% w/w), and reached the highest (1.34% w/w) in leaves harvested in July "early summer". Then-after, gradual decline in the content of quinic acid derivatives was evident in leaves collected during flowering stage in late summer "August-September" (0.84% w/w).

Chitosan application in the induction of water deficit tolerance in maize plants

The present research seeks to elucidate the feasibility of chitosan (CHT) in the induction of water deficit tolerance in different maize hybrids, contrasting tolerance to water restriction, tolerance and sensitivity. The maize plants were subjected to water deficit and foliar application of different chitosan doses (60, 100, 140, and 180 mg L-1) at the pre-flowering growth stage and evaluated during the stress period of fifteen days. To understand the induction behaviour of the tolerance to water restriction, biophysical parameters, such as water potential, relative water content and chlorophyll content, gas exchange, and biochemical assays, were quantified based on the activity of SOD, CAT, APX, and PAL antioxidant enzymes, lipid peroxidation activity and hydrogen peroxide content. Among the treatments, maize plants subjected to chitosan foliar application at a dose of 140 mg L-1 presented similar behavioural responses to plants under favourable irrigation conditions. Such positive responses are related to the high degree of activity of antioxidant enzymes, gas exchange and low levels of lipid peroxidation and hydrogen peroxide. The results support the potential use of CHT to increase tolerance to water stress.

Metabolite profiling of Andrographis paniculata (Burm. f.) Nees. young and mature leaves at different harvest ages using 1H NMR-based metabolomics approach

Andrographis paniculata (Burm. F.) Nees. is considered as the herb of the future due to its precious chemical compounds, andrographolide (ANDRO), neoandrographolide (NAG) and 14-deoxyandrographolide (DAG). This study aims to profile the metabolites in young and mature leaf at six different harvest ages using 1HNMR-based metabolomics combined with multivariate data analysis. Principal component analysis (PCA) indicated noticeable and clear discrimination between young and mature leaves. A comparison of the leaves stage indicated that young leaves were separated from mature leaves due to its larger quantity of ANDRO, NAG, DAG, glucose and sucrose. These similar metabolites are also responsible for the PCA separation into five clusters representing the harvest age at 14, 16, 18, 20, 22 weeks of leaves extract. Loading plots revealed that most of the ANDRO and NAG signals were present when the plant reached at the pre-flowering stage or 18 weeks after sowing (WAS). As a conclusion, A. paniculata young leaves at pre-flowering harvest age were found to be richer in ANDRO, NAG and DAG compared to mature leaves while glucose and choline increased with harvest age. Therefore, young leaves of A. paniculata should be harvested at 18 WAS in order to produce superior quality plant extracts for further applications by the herbal, nutraceutical and pharmaceutical industries.

Effect of nitrogen fertilization on flea beetle (Phyllotreta cruciferae) and cabbage seedpod weevil (Ceutorhynchus obstrictus) injury and crop yield in dry land canola

Nitrogen (N) availability is an important factor affecting the canola (Brassica napus L.) yield. While N fertilization is commonly used to enhance the yield and quality of canola, it is also known to influence the incidence of insect pests in the crop. The flea beetle Phyllotreta cruciferae (Goeze) and the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsh), are two economically important pests of canola in the northern Great Plains of the United States. This study investigated the effects of N fertilization (0, 56, 112 and 168 kg/ha) with or without insecticide seed treatment application on P. cruciferae and C. obstrictus injury levels, canola seed yield, and quality in replicated field trials at the two locations (Conrad and Sweet Grass) of north central Montana. The study showed that N fertilization had no influence on P. cruciferae and C. obstrictus injury levels, regardless of the study location or sampling date. However, insecticide seed treatment application significantly influenced P. cruciferae injury ratings at the both locations. In Conrad, insecticide-treated plots had significantly lower injury levels at the four leaf, pre-flower, and pod formation stages but without an effect at the cotyledon stage of canola plants when compared with untreated control plots. Similarly, in Sweet Grass, injury levels were significantly lower in insecticide-treated plots from cotyledon to pre-flowering stages but not at the pod stage of canola plants. In contrast, insecticide seed treatment had no impact on pod infestation rates by C. obstrictus at either location. Insecticide seed treatment, averaged over all the N rates, improved canola seed yield and quality parameters compared to the untreated plots.

Non-Invasive Phenotyping Reveals Genomic Regions Involved in Pre-Anthesis Drought Tolerance and Recovery in Spring Barley.

With ongoing climate change, drought events are becoming more frequent and will affect biomass formation when occurring during pre-flowering stages. We explored growth over time under such a drought scenario, via non-invasive imaging and revealed the underlying key genetic factors in spring barley. By comparing with well-watered conditions investigated in an earlier study and including information on timing, QTL could be classified as constitutive, drought or recovery-adaptive. Drought-adaptive QTL were found in the vicinity of genes involved in dehydration tolerance such as dehydrins (Dhn4, Dhn7, Dhn8, and Dhn9) and aquaporins (e.g. HvPIP1;5, HvPIP2;7, and HvTIP2;1). The influence of phenology on biomass formation increased under drought. Accordingly, the main QTL during recovery was the region of HvPPD-H1. The most important constitutive QTL for late biomass was located in the vicinity of HvDIM, while the main locus for seedling biomass was the HvWAXY region. The disappearance of QTL marked the genetic architecture of tiller number. The most important constitutive QTL was located on 6HS in the region of 1-FEH. Stage and tolerance specific QTL might provide opportunities for genetic manipulation to stabilize biomass and tiller number under drought conditions and thereby also grain yield.

Spatial distribution and seasonal variation of Limicolaria spp. infesting banana plantations in South West, Cameroon

This study was carried out as a prelude to elucidate a management plan that could limit residues in fruits and the environment without compromising quality. In order to meet our objectives, snails were randomly sampled from banana growth stages, different plant parts, residues, polythene bag-covered and uncovered banana bunches, and at different distances from the field edges. To assess seasonality of snail infestations, snails were sampled from the pre-flowering growth stage (January to September, 2012). The egg-laying and aestivating behaviours of snails were assessed by counting them from residues, weeds and soil. We recorded a higher number of snails on growth stages and plant parts in the rainy season compared to the dry season. The number of snails were significantly higher in the pre-flowering growth stages in the wet season (72.1 snails/plant) compared to those from the same stage in the dry season (0.88 snails/plant) (p=0.05). Although the highest number of snails were recorded on leaves in both seasons compared to other plants parts, the numbers were significantly higher on leaves during the rainy season compared to those in the dry season (p=0.05). Residues were the most preferred egg-laying and aestivating sites for snails while leaves on the ground haboured the highest number of snails in both seasons. We therefore concluded that focus on monitoring and management of the snails should be intensified during the rainy season with special attention on pre-flowered plants, uncovered bunches, and residues.

Growth and Productivity of Chickpea Genotypes under Different Soil Moisture Environment

The field experiment was conducted in concrete drought plots at crop physiology field lab, Department of Agronomy at CCS Haryana Agricultural University, Hisar during rabi season 2017-18 with the objective to study the effect of soil moisture environment on growth and productivity of chickpea genotypes in Factorial Randomized Block Design with three replications. In one block two irrigations one at pre-flowering stage and other at pod development stage were applied and in other block no post sown irrigation was applied. Significantly more number of days were taken to reach various phenological stages, taller plants and higher dry matter accumulation and yield was recorded under irrigated environment in comparison to rainfed environment. Among genotypes, H 13-09 had taken significantly more number of days to 50 percent flowering, 50 percent podding and maturity as compared to other genotypes. Highest seed yield (2097 kg/ha) was recorded in genotypes H 13-36 as compared to other genotypes; however, it was statistically at par with genotypes H 12-63(1979 kg/ha) and H 13-09(2011 kg/ha).

Antioxidant and phytochemical activities of Amaranthus caudatus L. harvested from different soils at various growth stages

This study aimed at profiling the biological activities of Amaranthus caudatus cultivated on different soils in a glasshouse experiment. Five soil types namely; sandy clay loam, silty clay loam, clayey loam, loam and control (unfractionated soil) were experimentally formulated from primary particles of clay, sand and silt following the United State Department of Agriculture’s (USDA) soil triangle technique. After harvesting at pre-flowering (61 days after planting), flowering (71 days after planting) and post-flowering (91 days after planting) stages, crude extracts were obtained with water and ethanol. Total flavonoids, phenolic and proanthocyanidin contents of the extracts, as well as their biological activities, were determined using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2 diphenyl-1-picrylhydrazyl ethanol (DPPH), nitric oxide and phosphomolybdate assays. It was observed that biological activity of A. caudatus varied with soil types, stages of maturity and solvents of extraction. The highest phytochemical yield was recorded in ethanolic extracts of clayey loam harvested prior to flowering and the same trend was replicated in the antioxidant properties of the plant. For optimal biological activity, it is recommended that clayey loam soil should be used for cultivation of A. caudatus and harvest should be made near flowering to capture high phytochemical yield from the species.

Dittrichia viscosa (Asterales: Asteraceae) as an Arthropod Reservoir in Olive Groves

Non-crop cultivated plants can provide agriculture with ecosystem services such as biological pest control and, a sound knowledge of the relationships between these plants and arthropod communities is important. Given its entomophilous characteristics, Dittrichia viscosa, a plant commonly found in the Mediterranean region, could potentially be used in integrated pest management systems. The aim of this study is to investigate arthropofauna associated with D. viscosa in olive groves during its preflowering, flowering and postflowering stages and to determine the possible relationships between different groups of arthropods. Using vacuum-sampling, the study was carried out on D. viscosa plants bordering and inside olive groves. The plants produced new leaves in April and flowered between August and October. Miridae, Aphididae, Hymenoptera parasitoids, Formicidae, Araneae and Aleyrodidae were the most abundant groups of arthropods collected during the preflowering and flowering stages. Plant phenology differentially influenced the arthropod populations of the different groups, with the Aleyrodidae family found to be more abundant during the preflowering stage, while Hymenoptera parasitoids were more numerous during the flowering stage. During the postflowering stage, the number of arthropods captured was very low. Numerous correlations between and within the different functional groups were observed throughout the life cycle of D. viscosa. Our results clearly show that D. viscosa plants in olive groves have great potential as a reservoir of different predators and Hymenoptera parasitoids and that these olive groves were not attacked by any D. viscosa-related phytophages.

Down-Regulation of CYP79A1 Gene Through Antisense Approach Reduced the Cyanogenic Glycoside Dhurrin in [Sorghum bicolor (L.) Moench] to Improve Fodder Quality.

A major limitation for the utilization of sorghum forage is the production of the cyanogenic glycoside dhurrin in its leaves and stem that may cause the death of cattle feeding on it at the pre-flowering stage. Therefore, we attempted to develop transgenic sorghum plants with reduced levels of hydrogen cyanide (HCN) by antisense mediated down-regulation of the expression of cytochrome P450 CYP79A1, the key enzyme of the dhurrin biosynthesis pathway. CYP79A1 cDNA was isolated and cloned in antisense orientation, driven by rice Act1 promoter. Shoot meristem explants of sorghum cultivar CSV 15 were transformed by the particle bombardment method and 27 transgenics showing the integration of transgene were developed. The biochemical assay for HCN in the transgenic sorghum plants confirmed significantly reduced HCN levels in transgenic plants and their progenies. The HCN content in the transgenics varied from 5.1 to 149.8 μg/g compared to 192.08 μg/g in the non-transformed control on dry weight basis. Progenies with reduced HCN content were advanced after each generation till T3. In T3 generation, progenies of two promising events were tested which produced highly reduced levels of HCN (mean of 62.9 and 76.2 μg/g, against the control mean of 221.4 μg/g). The reduction in the HCN levels of transgenics confirmed the usefulness of this approach for reducing HCN levels in forage sorghum plants. The study effectively demonstrated that the antisense CYP79A1 gene deployment was effective in producing sorghum plants with lower HCN content which are safer for cattle to feed on.

Morphophysiology of Tahiti lime grafted onto Sunki mandarin hybrids under salt stress

ABSTRACT This study aimed to evaluate the growth and physiology of citrus scion/rootstock combinations irrigated with saline water until the pre-flowering stage. The experiment was conducted in drainage lysimeters with capacity for 150 dm3, in randomized block design in a 2 x 10 factorial scheme, corresponding to two electrical conductivities of water (S1 = 0.3 and S2 = 3.0 dS m-1) and ten scion/rootstock combinations (nine hybrids and one commercial variety) grafted with Tahiti lime, in three repetitions and one plant per plot. Grafted seedlings were transplanted one year after sowing, subjected to salt stress from 15 days after transplanting until the pre-flowering period, and evaluated for gas exchanges and growth. The irrigation with 3.0 dS m-1 saline water did not influence the photosynthetic activity of the studied citrus scion/rootstock combinations until the pre-flowering. The genotype Santa Cruz Rangpur lime (LCRSTC) was more sensitive to irrigation water salinity in terms of growth. The least sensitive combinations to salinity were Tahiti lime grafted onto TSKFL x (LCR x TR) - 018, TSKFL x TRBK - 011 and TSKFL x TRBK - 30.

Gas Exchange and Nitrogen Compartmentalization of Eggplant under Nitrogen and Silicon Doses

To evaluate the effect of fertilization with N and Si on gaseous exchanges, dry mass, concentrations, accumulations and compartmentalization of nitrogen fractions in eggplant.&#x0D; The experimental design was a randomized entirely design, in a 5 x 4 factorial arrangement with four replications and one plant per plot, totaling 80 experimental units.&#x0D; The experiment was conducted in a protected environment at Center of Sciences and Agri-Food Technology of the Federal University of Campina Grande, Campus of Pombal, Paraiba, Brazil, between July and September 2016. The nitrogen doses applied was 25, 125, 250, 350 and 500 mg dm-3 and four silicon doses was 0, 75, 150 and 200 mg dm-3 both supplied by root. In pre-flowering stage were evaluated growth components; gas exchange, which are: photosynthesis, stomatal conductance, transpiration rate and intercellular CO2 concentration; levels and accumulation of fractions of nitrogen (NO3-, NH4+, and total), and the silicon concentration in the leaves. There was no significant interaction (p &gt;0.05) between the factors nitrogen and silicon doses for any of the evaluated variables. Nitrogen and silicon doses influenced the variables evaluated only independently each other. The nitrogen doses promoted increases in the photosynthetic rate and associated variables, dry matter yield of stem leaves and roots and in the concentration and accumulations of nitric, ammoniacal and total nitrogen in leaf, stem e roots and decrease the concentration of silicon in leaves. The silicon doses increased the leaf area index, the nitrate levels and accumulation in the roots and the silicon content in the leaves. In conclusion, the nitrogen supply increased the photosynthetic rate, dry mass and nitrogen accumulation and decreased the concentrations of silicon in leaf. Silicon did not interfered with growth of eggplant, however increased leaf area index, decreased nitrate levels and accumulations in the roots at lower doses of this element.

Response of fertility and agro-chemical on growth and yield of different varieties of Clusterbean

A field experiment was conducted during kharif season of 2013 to study response of clusterbean varieties to fertility levels and agro-chemicals at SKN College of Agriculture, Jobner. The experiment consisted of two varieties (RGC-1038 and RGC-1066), three treatments of fertility levels (control, 50% RDF and 100% RDF) and three treatments of agro-chemicals (control, thiourea 500 ppm twice at vegetative and pre flowering stage and thiourea 100 ppm twice at vegetative and pre flowering stage) thereby making eighteen treatment combinations tested in randomized block design with three replications. The results indicated that RGC 1066 variety recorded significantly higher plant height 60 DAS and at harvest and dry matter per meter row length at 30 DAS, 60 DAS and at harvest, number of pods/plant and seeds/pod, test weight, seed yield, stover yield and biological yield as compared to variety of RGC-1038. The result further indicated that application of fertilized 100% RDF significantly gave higher plant height at 60 DAS and at harvest similarly, dry matter per meter row length at 30 DAS, 60 DAS and at harvest, number of pods/plant and seeds/pod, test weight, seed yield, stover yield and biological yield recorded higher over control and fertilized with 50% RDF. Likewise, application of agro-chemical @ thiourea (500 ppm) significantly increased the plant height at 60 DAS and at harvest and dry matter per meter row length at 30 DAS, 60 DAS and at harvest, number of pods/plant and seeds/pod, test weight, seed yield, stover yield and biological yield and remained at par with the application of agro-chemical @ TGA (100 ppm) over control. However, plant height at 30 DAS remained materially unchanged under different varieties, fertility levels and agro-chemicals.

Proximate, mineral, vitamin and anti-nutrient content of Celosia argentea at three stages of maturity

The distribution of nutrients and metabolites in different organs and tissues is in a constant state of flux throughout the growth and development of a plant. This study was designed to evaluate the nutritional composition of Celosia argentea at three different stages of maturity to establish the best time of harvest for optimal nutritional benefits. Three growth stages: Pre-flowering (PRF), flowering (FLW) and post-flowering (PST) stages of two trials were investigated. Proximate, vitamins and anti-nutrients were performed using AOAC methods while minerals were determined using inductively coupled plasma-optical emission spectrometer (AOAC). For both trials, the PRF had the highest ash (28.15 ± 0.10% and 26.22 ± 0.10%) and crude protein (19.50 ± 0.17% and 25.80 ± 0.20%) contents. However, the PST had the highest carbohydrate (28.51 ± 0.20% and 36.16 ± 0.22%), crude fiber (33.41 ± 0.87% and 25.20 ± 0.20%) and energy (435.28 ± 27.6% and 426.08 ± 1.08%) but was the lowest in fat and moisture (8.43 ± 0.15% and 6.35 ± 0.09%) contents respectively. In the mineral composition, there was no marked demarcation in the amount of Mg, Na and Fe. However, the PRF, had the highest amount of Ca, K, P and Cu. Zinc was highest at the flowering stage of growth, while Vitamins A, C and E concentration decreased as the plant approached maturation. PRF stage had the highest vitamin concentrations; alkaloid and saponin contents were highest at the PRF stage while oxalate and phytate content was not dependent on growth stages. The study revealed that although, the nutrient composition of Celosia argentea is strongly influenced by maturity stages, the best age of harvest, would be determined by the deficiency to be corrected.

The foliar application of a mixture of semisynthetic chitosan derivatives induces tolerance to water deficit in maize, improving the antioxidant system and increasing photosynthesis and grain yield

Research has shown that chitosan induces plant stress tolerance and protection, but few studies have explored chemical modifications of chitosan and their effects on plants under water stress. Chitosan and its derivatives were applied (isolated or in mixture) to maize hybrids sensitive to water deficit under greenhouse conditions through foliar spraying at the pre-flowering stage. After the application, water deficit was induced for 15 days. Analyses of leaves and biochemical gas exchange in the ear leaf were performed on the first and fifteenth days of the stress period. Production attributes were also analysed at the end of the experiment. In general, the application of the two chitosan derivatives or their mixture potentiated the activities of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaiacol peroxidase at the beginning of the stress period, in addition to reducing lipid peroxidation (malonaldehyde content) and increasing gas exchange and proline contents at the end of the stress period. The derivatives also increased the content of phenolic compounds and the activity of enzymes involved in their production (phenylalanine ammonia lyase and tyrosine ammonia lyase). Dehydroascorbate reductase and compounds such as total soluble sugars, total amino acids, starch, grain yield and harvest index increased for both the derivatives and chitosan. However, the mixture of derivatives was the treatment that led to the higher increase in grain yield and harvest index compared to the other treatments. The application of semisynthetic molecules derived from chitosan yielded greater leaf gas exchange and a higher incidence of the biochemical conditions that relieve plant stress.

Photosynthetic Responses to High Temperature and Strong Light Suggest Potential Post-flowering Drought Tolerance of Sorghum Japanese Landrace Takakibi.

Sorghum [Sorghum bicolor (L.) Moench] is a C4 crop known to be adaptable to harsh environments such as those under high temperature and water deficit. In this study, we focused on a Japanese sorghum landrace Takakibi (NOG) and employed chlorophyll fluorescence measurements to assess its response to environmental stress. Comparison of photosynthetic rate evaluated using two parameters (effective quantum yield and electron transfer rate) indicated that NOG showed less activity than BTx623 in the pre-flowering stage, which was consistent with the higher susceptibility of NOG seedlings to drought than BTx623. The observed differences in photosynthetic activity between the two cultivars were detectable without drought conditions on days with high temperature and strong light. Interestingly, the photosynthetic activity of NOG leaves in stress conditions increased soon after heading, and the trend was similar to that in BTx642, a well-characterized post-flowering drought-tolerant cultivar. In contrast, BTx623 showed a gradual decline in photosynthetic rate. Thus, we inferred that Japanese Takakibi has the potential to show pre-flowering drought susceptibility and post-flowering drought tolerance, through which it adapts to local climates with high temperature and strong light at harvest.

The effects of rain shelter coverings on the vegetative growth and fruit characteristics of Chinese cherry (Prunus pseudocerasus Lindl.)

Throughout the whole process from the onset of blossoming to fruit maturity, rain and hail can cause severe losses in cherry (Prunus pseudocerasus Lindl.) yields, e.g., up to 90%, under the conventional shelter-free (control) conditions in Southwest China. Recently, rain shelters have been increasingly applied worldwide to prevent flowers and fruit from damage by excessive rainfall and hail, and the utility of rain shelters was preliminarily proven to benefit cherry production due to yield improvements, especially in Southwest China. However, the effects of rain shelter coverings on the vegetative growth, photosynthesis and fruit characteristics of cherry have not yet been fully explored. In the present study, the 5-year-old field-grown plants were covered with polyethylene (PE) film from the preflowering stage until fruit harvested for one year (1a-shelter) or two years (2a-shelter) as part of trials in Guizhou Province, Southweste China. Compared with that under the control conditions, the leaf area under 1a- and 2a-shelter conditions significantly increased by 23.0% and 26.87%, respectively, at the 55 days after flowering (DAF) (DAF55); conversely, the leaf thickness clearly decreased by 17.67% and 19.7%, respectively. Similar trends in leaf area and thickness were also observed under the 2a-shelter, but no marked differences occurred between the 1a-shelter and 2a-shelter. Regardless of the covering cycle, the rain shelters somewhat promoted shoot elongation, although the differences were not statistically significant. Compared with the control, the 1a-shelter and 2a-shelter caused considerable increases in chlorophyll contents in the leaves. Interestingly, the rain shelters strongly increased the carotenoid (Cx) contents in the leaves under both the 1a- shelter and 2a-shelter, indicating an obvious improvement in the ability to use weak sunlight. Compared with those in the control, the diurnal fluctuations in the photosynthetic rate (Pn) of the leaves under both 1a- shelter and 2a-shelter characterized by a single peak; the Pn of the control exhibited a typical noon-slump pattern, which accordingly led to an increase in the total daily photosynthetic accumulation within the sheltered leaves. Compared with those in the control, the mean weight and size of fruit from plants under the shelters significantly increased, and the cracking rate greatly decreased from 95% (control) to approximately 4% (1a-shelter and 2a-shelter), giving rise to an approximately fourfold increase in yield of the sheltered trees. Furthermore, the contents of the total soluble solids (TSSs), soluble sugars (SSs), ascorbic acid (AsA) and anthocyanins of the sheltered fruit differentially increased; conversely, the rain shelters reduced the titratable acid (TA) titers. Therefore, rain shelter cultivation may substantially contribute to the total photosynthetic accumulation and increased fruit yield and has no obvious negative effects on the vegetative growth or fruit quality of cherry trees in Southwest China, which may benefit the cherry industry in this region.

Spikelet fertility and heat shock transcription factor (Hsf) gene responses to heat stress in tolerant and susceptible rice (Oryza sativa L.) genotypes

AbstractThe reproductive stage of rice is the most sensitive to heat stress, which can lead to spikelet sterility. Thus, heat-tolerant and heat-susceptible genotypes were used to investigate their differences in terms of phenotypic responses and expression changes ofHsfgenes at the pre-flowering stage under heat stress. Results clearly showed that panicles had the highest temperature compared with other plant parts under both natural and heated conditions. However, the temperatures of tolerant and susceptible genotypes were not significantly different. In terms of spikelet fertility, the tolerant lines M9962 and M7988 had high seed set because their anther dehiscence, pollen viability and pollen germination were only slightly affected. In contrast, the susceptible line Sinlek showed severe effects at all steps of fertilization, and the pollen viability of M7766 was slightly affected under heat stress but was more affected in terms of anther dehiscence and pollen germination. Both susceptible lines showed dramatically decreased seed set. In addition, the expression of sixHsfAgenes in the flag leaves and spikelets at the R2 stage of plants under heat stress showed different responses. Notably, expression of theHsfA2agene was predominantly upregulated in the flag leaf and spikelets under heat stress in M9962. Therefore, it can be concluded that heat stress has severe effects on the stamen, and that different genotypes have different susceptibilities to heat stress.