Significant Reduction In Plant Height Research Articles

Morphological, anatomical, and transcriptomics analysis reveals the regulatory mechanisms of cassava plant height development

BackgroundCassava is one of three major potato crops and the sixth most important food crop globally. Improving yield remains a primary aim in cassava breeding. Notably, plant height significantly impacts the yield and quality of crops; however, the mechanisms underlying cassava plant height development are yet to be elucidated.ResultsIn this study, we investigated the mechanisms responsible for cassava plant height development using phenotypic, anatomical, and transcriptomic analyses. Phenotypic and anatomical analysis revealed that compared to the high-stem cassava cultivar, the dwarf-stem cassava cultivar exhibited a significant reduction in plant height and a notable increase in internode tissue xylem area. Meanwhile, physiological analysis demonstrated that the lignin content of dwarf cassava was significantly higher than that of high cassava. Notably, transcriptome analysis of internode tissues identified several differentially expressed genes involved in cell wall synthesis and expansion, plant hormone signal transduction, phenylpropanoid biosynthesis, and flavonoid biosynthesis between the two cassava cultivars.ConclusionsOur findings suggest that internode tissue cell division, secondary wall lignification, and hormone-related gene expression play important roles in cassava plant height development. Ultimately, this study provides new insights into the mechanisms of plant height morphogenesis in cassava and identifies candidate regulatory genes associated with plant height that can serve as valuable genetic resources for future crop dwarfing breeding.

Deer grazing drove an assemblage‐level evolution of plant dwarfism in an insular system

Abstract Plant dwarfism, a syndrome characterised by a significant reduction in plant height and organ size, is a widely observed pattern of stress‐tolerant life‐form evolution that results from local adaptation to harsh environmental conditions. The drivers of assemblage‐level dwarfism have primarily been attributed to abiotic factors, such as low temperature, aridity, poor soil fertility or frequent fires. While biotic factors such as grazing pressure from herbivores can contribute to the establishment of plant dwarfism, these factors have rarely been tested at assemblage levels. Focusing on a dwarf plant assemblage comprising over 80 taxa on a small continental island in Japan with a high deer density, we hypothesised that historical deer grazing could also be a factor contributing to the large‐scale convergent evolution of dwarfism. To test this hypothesis, we measured the size of 1908 individual plants of 40 taxa pairs, comprising both palatable and unpalatable pairs from the island and their counterpart taxa from neighbouring regions, and sought to assess which factors (i.e. low solar radiation, estimated divergence time, low nutrient conditions and grazing pressure from deer) may have contributed to the formation of the dwarf plant assemblage on the island. We also performed genetic analysis to infer the time frames for the establishment of dwarf taxa. Statistical analyses revealed that plant size was significantly reduced mainly among the palatable taxa growing on the island, with preferential grazing by deer being identified as the most significant factor influencing plant size. Furthermore, genetic analyses revealed that dwarf ecotypes may have evolved over tens of thousands of years. Synthesis: To the best of our knowledge, this study is the first to demonstrate that interactions with herbivores can shape the assemblage‐level convergence of plant dwarfism. These findings enhance our current understanding of the formation of plant functional diversity.

Amelioration of chromium toxicity in wheat plants through exogenous application of nano silicon

Chromium (Cr) contamination in agricultural soils poses a risk to crop productivity and quality. Emerging nano-enabled strategies show great promise in remediating soils contaminated with heavy metals and enhancing crop production. The present study was aimed to investigate the efficacy of nano silicon (nSi) in promoting wheat growth and mitigating adverse effects of Cr-induced toxicity. Wheat seedlings exposed to Cr (K2Cr2O7) at a concentration of 100 mg kg−1 showed significant reductions in plant height (29.56%), fresh weight (35.60%), and dry weight (38.92%) along with enhanced Cr accumulation in roots and shoots as compared to the control plants. However, the application of nSi at a concentration of 150 mg kg−1 showcased substantial mitigation of Cr toxicity, leading to a decrease in Cr accumulation by 27.30% in roots and 35.46% in shoots of wheat seedlings. Moreover, nSi exhibited the capability to scavenge oxidative stressors, such as hydrogen peroxide (H2O2), and malondialdehyde (MDA) and electrolyte leakage, while significantly enhancing gas exchange parameters, total chlorophyll content, and antioxidant activities (enzymatic and nonenzymatic) in plants grown in Cr-contaminated soil. This study further found that the reduced Cr uptake by nSi application was due to downregulating the expression of HMs transporter genes (TaHMA2 and TaHMA3), alongwith upregulating the expression of antioxidant-responsive genes (TaSOD and TaSOD). The findings of this investigation highlight the remarkable potential of nSi in ameliorating Cr toxicity. This enhanced efficacy could be ascribed to the distinctive size and structure of nSi, which augment its ability to counteract Cr stress. Thus, the application of nSi could serve as a viable solution for production of crops in metal contaminated soils, offering an effective alternative to time-consuming and costly remediation techniques.

Comparative transcript abundance of gibberellin oxidases genes in two barley (Hordeum vulgare) genotypes with contrasting lodging resistance under different regimes of water deficit.

Barley (Hordeum vulgare ) is the world's fourth most important cereal crop, and is particularly well adapted to harsh environments. However, lodging is a major productivity constraint causing 13-65% yield losses. Gibberellic acid (GA) homeostatic genes such as HvGA20ox, HvGA3ox and HvGA2ox are responsible for changes in plant phenotype for height and internodal length that contribute towards lodging resistance. This study explored the expression of different HvGAox transcripts in two contrasting barley genotypes (5-GSBON-18, lodging resistant; and 5-GSBON-70, lodging sensitive), which were sown both under controlled (hydroponic, completely randomised factorial design) and field conditions (split-plot, completely randomised block design) with two irrigation treatments (normal with three irrigation events; and water deficit with one irrigation event). In the hydroponic experiment, expression analysis was performed on seedlings at 0, ¾, 1½, 3 and 6h after application of treatment. In the field experiment, leaf, shoot nodes and internodes were sampled. Downregulation of HvGA20ox.1 transcript and 2-fold upregulation of HvGA2ox.2 transcript were observed in 5-GSBON-18 under water deficit conditions. This genotype also showed a significant reduction in plant height (18-20%), lodging (<10%), and increased grain yield (15-18%) under stress. Utilisation of these transcripts in barley breeding has the potential to reduce plant height, lodging and increased grain yield.

Flood Tolerance of Hybrid Napier (Pennisetum purpureum x Pennisetum glaucum) Cultivars

A pot culture study was conducted from February to May 2020 at the Agronomy Farm, Department of Agronomy, College of Agriculture, Vellanikkara, Kerala to study the effects of short-term flooding on the growth, physiology, and yield of four high-yielding cultivars of hybrid napier (Pennisetum purpureum x Pennisetum glaucum) cultivated in Kerala. The experiment followed a 4 x 2 factorial Completely Randomized Design with three replications. The treatments comprised two factors: varieties and flooding treatments. The four hybrid napier varieties used in the study were CO-3 (V1), CO-5 (V2), IGFRI -3 (V3), and Suguna (V4). The flooding treatments included no flooding (F0) as a control and short-term flooding stress treatment (F1) at three different growth stages: 30 days after planting (DAP), 60 DAP and just after the first harvest (75 DAP). Flooding stress was imposed for seven days by inundating water in the pots up to 3-4 cm above the soil level. Flooding at all three stages resulted in a significant reduction in plant height, tiller number, leaf number and above-ground biomass for all varieties. A severe reduction in growth and yield parameters was observed when flooding stress was imposed immediately after the first harvest. Among the varieties, CO-5 had the tallest plants, followed by Suguna, CO-3, and IGFRI-3. When exposed to flooding stress, variety CO-5 was also found to be significantly superior in terms of above-ground biomass production, followed by CO-3. Superoxide dismutase (SOD) activity increased in all varieties due to flooding stress, with a pronounced increase observed in Suguna. Variety CO-5, which exhibited greater plant height and above-ground biomass production, was found to be more tolerant to flooding stress, while variety IGFRI-3, with a dwarf plant stature and the lowest biomass yield, was identified as sensitive to short-term flooding stress.

An assessment of the physicochemical characteristics and essential oil composition of Mentha longifolia (L.) Huds. exposed to different salt stress conditions.

Salt stress adversely influences growth, development, and productivity in plants, resulting in a limitation on agriculture production worldwide. Therefore, this study aimed to investigate the effect of four different salts, i.e., NaCl, KCl, MgSO4, and CaCl2, applied at various concentrations of 0, 12.5, 25, 50, and 100 mM on the physico-chemical properties and essential oil composition of M. longifolia. After 45 days of transplantation, the plants were irrigated at different salinities at 4-day intervals for 60 days. The resulting data revealed a significant reduction in plant height, number of branches, biomass, chlorophyll content, and relative water content with rising concentrations of NaCl, KCl, and CaCl2. However, MgSO4 poses fewer toxic effects than other salts. Proline concentration, electrolyte leakage, and DPPH inhibition (%) increase with increasing salt concentrations. At lower-level salt conditions, we had a higher essential oil yield, and GC-MS analysis reported 36 compounds in which (-)-carvone and D-limonene covered the most area by 22%-50% and 45%-74%, respectively. The expression analyzed by qRT-PCR of synthetic Limonene (LS) and Carvone (ISPD) synthetic genes has synergistic and antagonistic relationships in response to salt treatments. To conclude, it can be said that lower levels of salt enhanced the production of essential oil in M. longifolia, which may provide future benefits commercially and medicinally. In addition to this, salt stress also resulted in the emergence of novel compounds in essential oils, for which future strategies are needed to identify the importance of these compounds in M. longifolia.

Genetic Effects of GA-Responsive Dwarfing Gene Rht13 on Plant Height, Peduncle Length, Internodal Length and Grain Yield of Wheat under Drought Stress.

Reduction in plant height is generally associated with an increase in lodging resistance, drought tolerance and grain yield of wheat worldwide. Historically, a significant increase in grain yield was observed through the introduction of semi-dwarf wheat varieties utilizing the gibberellic acid-insensitive Rht genes (Rht1 or Rht2). The gibberellic acid sensitive (GA-sensitive) reduced height (Rht) genes are available that are alternatives to gibberellic acid insensitive (GA-insensitive) Rht genes, having a neutral effect on coleoptile length seedling vigor suggesting their potential in using alone or in combination with GA-insensitive Rht genes to improve grain yield and drought tolerance in wheat. This study was conducted to evaluate parents and F1 crosses under drought stress. The crossing was done using line × tester mating design, comprising eight lines and five testers having different GA-sensitive and GA-insensitive Rht genes. Parents and F1 crosses were sown in the field under RCBD with three replications in normal and drought stress. Data were recorded for morpho-physiological traits. The mean comparison showed significant differences among parents and hybrids for most of the studies' traits. The general combining ability showed that line 1 is the good general combiner for days to heading, lodging (%), plant height, peduncle length, internodal length and days to maturity under normal conditions while L5 was the good general cobiner for chlorophyll contents and stomatal conductance both under normal and drought stress. The spcaicfic combing ability estimases showed that the cross L1 × T1 was best for days to heading, lodging (%), plant height and internodal length both under normal and drought stress. F1 hybrids showed a significant reduction in plant height (18-25%), peduncle length (20-28%) and increased grain yield (15-18%) under drought stress. Expression analysis showed upregulation of Rht13 at the middle part of the peduncle internode under drought stress. From the expression analysis, five crosses were selected, and their segregating population was raised and space-plated. Rht13 genes reduced plant height (-30 to -45%), peduncle length (-30 to -53%), peduncle internode length (-28% to -48%), increased spike length (+20% to +50%), number of grains per spike (+17 to +26%) and grain yield per plant (+29% to +50%) compared to Rht1 gene. These results suggested the possibility of using the GA-sensitive Rht13 gene for the development of high-yielding and drought-tolerant wheat varieties.

Transcriptomic profiling of wheat stem during meiosis in response to freezing stress.

Low temperature injury in spring has seriously destabilized the production and grain quality of common wheat. However, the molecular mechanisms underlying spring frost tolerance remain elusive. In this study, we investigated the response of a frost-tolerant wheat variety Zhongmai8444 to freezing stress at the meiotic stage. Transcriptome profiles over a time course were subsequently generated by high-throughput sequencing. Our results revealed that the prolonged freezing temperature led to the significant reductions in plant height and seed setting rate. Cell wall thickening in the vascular tissue was also observed in the stems. RNA-seq analyses demonstrated the identification of 1010 up-regulated and 230 down-regulated genes shared by all time points of freezing treatment. Enrichment analysis revealed that gene activity related to hormone signal transduction and cell wall biosynthesis was significantly modulated under freezing. In addition, among the identified differentially expressed genes, 111 transcription factors belonging to multiple gene families exhibited dynamic expression pattern. This study provided valuable gene resources beneficial for the breeding of wheat varieties with improved spring frost tolerance.

Effects of Cucumber Mosaic Virus on Yield Components and Yield of Bambara Groundnut

Bambara groundnut (Vigna subterranean L. Verdc) is a leguminous plant and its seeds are highly nutritious and can be considered as complete food. In addition to being a neglected crop; its production is limited by several constraints among which virus diseases are the most implicated. In order to contribute to the improvement of bambara groundnut in Nigeria, landraces of bambara groundnut were screened for resistance to Cucumber mosaic virus (CMV), one of the most damaging viruses in grain legumes. Treatments consisted of five landraces namely Black, Brown, Cream, Red nav, and Zebra coloured got from local farmers. These were arranged in Randomised Complete Block Design, with three replicates. Seedlings were infected with CMV isolate three weeks after sowing (WAS), during the 2019 and 2020 trials. The infected plants exhibited various symptoms of chlorosis, leaf deformation, growth retardation, and plant stunting. The sCMV caused significant reduction in plant height, the number of branches, leaves, pods, and seeds weight. In the 2019 and 2020 trials, 100 % incidence with the highest severity was observed in the Bambara groundnut landraces. Disease incidence varied between 41.6% in “Black” and 95.8 % in “Cream,” while disease severity was higher in “Cream” and “Red nav” with 5.0 respectively. “Black” and “Zebra” were the tallest with 16.8 cm among the infected as well as disease-free with 22.6 cm tall plants. “Black” landrace produced the highest number of pods in both CMV infections with 21 and disease-free with 33 pods respectively. Conversely, the number of days to flowering of 43 days was highest in infected plants of “Black”. The “Black” and “Zebra” landraces recorded uniform seed weights and the highest seed weight under CMV infection with 1.7 g per plant. The impact of the virus on yield loss was lowest in “Black” and “Zebra” landraces which indicated their possible use in the management of Cucumber mosaic virus disease in Bambara groundnut.

Response of banana (Musa spp.) to drought stress based on phenotypic and physiological traits

ABSTRACT Banana (Musa spp.), an important staple food in the tropical and subtropical regions, is highly susceptible to drought. Developing drought-tolerant bananas using available germplasm offers a long-term solution to mitigate drought effects. The East and Central Africa Banana Germplasm Collection in Uganda contains genetically diverse genotypes whose potential for drought tolerance breeding is yet to be established. This study aimed to determine the response of 14 Musa spp. genotypes to drought stress using phenotypic and physiological traits in order to select promising genotypes for use in breeding. Two genotypes with a known reaction to water deficit conditions were included as local checks. Three-month-old tissue culture-derived plantlets were completely deprived of water for four weeks while control plants were regularly irrigated back to field capacity, and both sets maintained under screen-house conditions. Drought stress resulted in significant reductions in plant height, total leaf area, number of leaf cigars and functional leaves, total dry matter, chlorophyll and relative water content. Water use efficiency (WUE) of 12 genotypes increased under stress conditions. Stomatal conductance was affected by the genotype-porometer reading time interaction. Genotype “ITC.0987” was the most tolerant, considering that moisture stress had the least effect on its above-ground growth. Among the improved diploids, “TMB2x9722-1” had the least total dry matter reduction and highest WUE, while “TMB2x9172” showed the least decrease in relative water content and highest root-shoot ratio increase under stress. Thus, “ITC.0987”, “TMB2x9722-1” and “TMB2x9172” are essential drought-tolerant candidates that may be utilized in breeding.

Use of plant growth regulators to reduce 2-methyl-4-chlorophenoxy acetic acid-Na (MPCA-Na) damage in cotton (Gossypium hirsutum)

Background2-methyl-4-chlorophenoxy acetic acid-Na (MPCA-Na) is a phenoxy carboxylic acid selective hormone herbicide that is widely used in the crop fields. However, drift of MPCA-Na during application is highly damaging to cotton (Gossypium hirsutum) and other crop plants. This study was carried out from 2019 to 2020 to determine the effects of different concentrations of MPCA-Na on physiological and metabolic activities besides growth and yield of cotton plants at seedling, budding, flowering and boll stages. Moreover, we evaluated the different combinations of 24-epibrassinolide, gibberellin (GA3), phthalanilic acid and seaweed fertilizer to ameliorate herbicide damage.Results2-methyl-4-chlorophenoxy acetic acid-Na (MPCA-Na) exposure caused a decrease in the chlorophyll content, and an increase in the soluble protein content, Malondialdehyde (MDA) content and protective enzyme activity. It also caused significant reductions in plant height, boll number and the single boll weight at the seedling and budding stages, but had little effects on plant height and the single boll weight at flowering and boll stage. Under the maximum recommended dose of MPCA-Na (130 g/L), the number of cotton bolls at seedling and budding stages decreased by 75.33 and 79.50%, respectively, and the single boll weight decreased by 46.42 and 36.31%, respectively. Nevertheless, the number of G. hirsutum bolls and single boll weight at flowering and boll stage decreased by 48.15 and 5.38%, respectively. Application of plant growth regulators decreased the MDA content, and increased chlorophyll, soluble protein content and protective enzyme activity, and alleviated MCPA-Na toxicity. Positive effects in case of growth regulators treated plants were also observed in terms of G. hirsutum yield. Phthalanilic acid + seaweed fertilizer, 24-epibrassinolide + seaweed fertilizer, and GA3 + seaweed fertilizer should be used at the seedling, budding, and flowering and boll stages, respectively.ConclusionsThe results of current study suggest that certain plant growth regulators could be used to alleviate MPCA-Na damage and maintain G. hirsutum yield. When the cotton exposed to MCPA-Na at the seedling stage, it should be treated with phthalanilic acid + seaweed fertilizer, while plants exposed at the budding stage should be treated with 24-epibrassinolide + seaweed fertilizer, and those exposed at the flowering and boll stages should be treated with GA3 + seaweed fertilizer to mitigate stress.

Salt Stress Induces Changes in Physiological Characteristics, Bioactive Constituents, and Antioxidants in Kenaf (Hibiscus cannabinus L.).

Salinity stress is a major environmental threat in agricultural systems. Kenaf is a promising crop for the future for cultivation in salinity-affected soils because of its high phytoremediation potential. The current study aimed to investigate the effects of salt stress using six different sodium chloride (NaCl) concentrations (0, 50, 100, 150, 200, and 250 mM) on the plant growth, physiological characteristics, bioactive constituents, and antioxidant capacity of H. cannabinus. The results indicated that the NaCl stress induced significant reductions in plant height and in the dry and fresh weights of the leaf tissue. In addition, the K, Ca, Mg, and P concentrations in this tissue also decreased under NaCl stress treatment conditions. In contrast, the NaCl stress led to the accumulation of hydrogen peroxide (H2O2), superoxide anion (O2•−), malondialdehyde (MDA), proline, total soluble sugar, and total soluble protein. Under NaCl stress, the levels of antioxidants, including phenolics and flavonoids, also increased. The gas chromatography–mass spectrometry (GC-MS) results showed that the volatile compounds, including heptacosane, 1-octadecanesulphonyl chloride, and tetratetracontane, were induced under the NaCl stress treatment. Furthermore, the salt stress significantly improved the antioxidant capacity of the leaf extracts. These findings may provide insight into how H. cannabinus plants respond to salt stress and may help improve its medicinal value under salt stress.

Exogenously Applied Proline Enhances Morph-Physiological Responses and Yield of Drought-Stressed Maize Plants Grown Under Different Irrigation Systems.

The exogenous application of osmoprotectants [e.g., proline (Pro)] is an important approach for alleviating the adverse effects of abiotic stresses on plants. Field trials were conducted during the summers of 2017 and 2018 to determine the effects of deficit irrigation and exogenous application of Pro on the productivity, morph-physiological responses, and yield of maize grown under two irrigation systems [surface irrigation (SI) and drip irrigation (DI)]. Three deficit irrigation levels (I100, I85, and I70, representing 100, 85, and 70% of crop evapotranspiration, respectively) and two concentrations of Pro (Pro1 = 2 mM and Pro2 = 4 mM) were used in this study. The plants exposed to drought stress showed a significant reduction in plant height, dry matter, leaf area, chlorophyll content [soil plant analysis development (SPAD)], quantum efficiency of photosystem II [Fv/Fm, Fv/F0, and performance index (PI)], water status [membrane stability index (MSI) and relative water content (RWC)], and grain yield. The DI system increased crop growth and yield and reduced the irrigation water input by 30% compared with the SI system. The growth, water status, and yield of plants significantly decreased with an increase in the water stress levels under the SI system. Under the irrigation systems tested in this study, Pro1 and Pro2 increased plant height by 16 and 18%, RWC by 7 and 10%, MSI by 6 and 12%, PI by 6 and 19%, chlorophyll fluorescence by 7 and 11%, relative chlorophyll content by 9 and 14%, and grain yield by 10 and 14%, respectively, compared with Pro0 control treatment (no Pro). The interaction of Pro2 at I100 irrigation level in DI resulted in the highest grain yield (8.42 t ha–1). However, under the DI or SI system, exogenously applied Pro2 at I85 irrigation level may be effective in achieving higher water productivity and yield without exerting any harmful effects on the growth or yield of maize under limited water conditions. Our results demonstrated the importance of the application of Pro as a tolerance inducer of drought stress in maize.

Prioritisation of damaging weed biological control agents for prickly acacia (Vachellia nilotica subsp. indica) based on insect exclusion studies in the native range

Prickly acacia, Vachellia nilotica subsp. indica (Benth.) Kyal. & Boatwr. (Fabaceae), native to India, is a target for biological control in Australia. Native range insecticide exclusion studies were conducted at two sites (Coimbatore and Thoppur) in India to evaluate the impact of insect herbivores on prickly acacia, to prioritise agents. At each site, prickly acacia plants were either exposed to or protected from insect herbivores and the incidence of insects were recorded at quarterly intervals. More insect species occurred at Thoppur (12) than at Coimbatore (9) and among them the scale insect Anomalococcus indicus Ayyar (Hemiptera: Lecanodiaspididae) was the predominant species at both sites. Insect herbivory significantly reduced plant height, basal stem diameter, number of branches, the number of leaves, and stem biomass at Coimbatore, while the impact was evident only for plant height at Thoppur. However, there were significant reductions in plant height (38–55%), basal stem diameter (20–31%), number of branches (21–45%), number of leaves (79–99%), leaf biomass (81–96%), stem biomass (67–84%) and root biomass (61–84%) in plants infested with A. indicus than in plants without A. indicus in insects excluded plots. Infestation by A. indicus resulted in 18 and 27% plant mortality in Coimbatore and Thoppur, respectively. Based on potential impact, A. indicus was prioritised for importation and detailed host-specificity testing in Australia.

Interactions among cereal cyst nematode Heterodera filipjevi, dryland crown rot Fusarium culmorum, and drought on grain yield components and disease severity in bread wheat

The cereal cyst nematode (CCN) Heterodera and crown rot caused by Fusarium species limit cereal production and yield potential. Losses increase when CCN and crown rot occur together, especially under water stress conditions. The objective of this study was to investigate the interactions among Heterodera filipjevi, Fusarium culmorum, and drought on a set of wheat germplasm with differing levels of resistance/tolerance to CCN, crown rot and drought. Plant emergence was significantly reduced (56% seedling death) when seeds were planted in a water stress environment where F. culmorum and H. filipjevi were present. Crown rot was more severe under water stress compared with Fusarium inoculation alone. The number of cysts fell significantly when H. filipjevi was co-inoculated with F. culmorum, revealing an antagonistic interaction between the nematode and fungus. The highest number of cysts was found on the susceptible accession ‘Seri’ under water stress conditions. Water stress caused a significant reduction in plant height, while F. culmorum inoculation did not, unless combined with water stress. Yield components were significantly reduced by each of the single stresses and losses were greater when plants were exposed to double or triple stresses. Water stress and F. culmorum inoculation caused a significant reduction in spike weight and seeds per spike. The chlorophyll content of wheat leaves was negatively affected by water stress and inoculation by both nematode and fungus. In conclusion, water stress exacerbates the damage caused by CCN and crown rot, and planting drought-resistant varieties would be an ideal solution to reduce losses.

SEED GERMINATION BEHAVIOUR, SEEDLING GROWTH, MORPHO-PHYSIOLOGICAL AND YIELD ATTRIBUTES OF RICE GROWN IN CADMIUM-ADDED SOIL

An experiment was conducted to investigate the effect of different levels of cadmium (Cd) stress on germination, morphology, physiology and yield of rice. There were five treatments, viz. control (no Cd), 0.5 mM CdCl2, 1 mM CdCl2, 1.5 mM CdCl2 and 2 mM CdCl2, carried out by a randomized complete block design (RCBD) with three replications. Cadmium stress caused a significant reduction of plant height and tillers hill-1 in a dose-dependent manner. The highest decline of relative water content and SPAD value was found at 1.5 mM (11 and 16%) and 2 mM (14 and 19%) Cd stress compared to the control. The number of effective tillers hill-1, filled grains panicle-1, 1000-grain weight, length of panicle, grain yield and straw yield reduced significantly by 44, 32, 15, 24, 37 and 45%, respectively, over the control. Germination and seedling-related parameters were recorded 10 days after germination. The lowest germination percentage (27%), germination index (27%) and seedling vigour index (49%) were observed at the highest level of Cd stress in comparison to the control. Cadmium stress resulted in maximum abnormal seedlings and markedly reduced length of root and shoot as well as their fresh and dry weight. Root shoot ratio showed differential responses to Cd stress. Thus, it can be concluded that a higher level of Cd in soil has a detrimental effect on seed germination, morphology, physiology and yield of rice.

Effect of Gamma Irradiation on Survivability, Growth Performances and Floral Characters of Jasminum officinale (Samanpichcha)

Physical mutagenesis is an effective mutational breeding method for improving various growth and floral characteristics of ornamental plants. The experiment was undertaken with an objective to investigate the effect of various dosages of gamma irradiation on survivability, growth and floral characteristics of Jasminum officinale plants raised by rooted cuttings. The 60CO Gamma irradiation source at Horticultural Crop Research and Developmental Institute, Gannoruwa was used to expose rooted plants to different dosages such as 0Gy, 17Gy, 21Gy, 25Gy, 29Gy and 33Gy. A Complete Randomized Design with four replicates having 10 plants for each replicate was practiced. The results revealed that gamma irradiation dosage from 25Gy to 33Gy significantly decreased the survivability of J. officinale plants (P&lt;0.05). LD50 of gamma radiation on J. officinale was occurred around 33Gy at maturity stage. Plant height and shoot length were significantly reduced by gamma irradiation dosages of 17Gy to 33Gy compared to the control and significant reduction of shoot number was observed at 33Gy. Gamma irradiation with 17Gy dosage, it showed a significant reduction in petal width (0.82 cm) of flowers. None of the other dosages were able to develop a change in the floral characteristics of J. officinale. The study showed that 33Gy gamma irradiated plant, it is having significant reduction of plant height, number of shoots and shoot length hence it could be domesticated as a dwarf and potted plant.

TRINEXAPAC-ETHYL REDUCES PLANT HEIGHT AND SEED YIELD IN FORAGE SORGHUM

Forage sorghum presents tall plants, what makes mechanicalseed harvesting a difficult task. Plant hormones can reduce plant height andfacilitate the harvesting. Thus, the objective of this study was to evaluatethe effect of the growth regulator trinexapac-ethyl on plant height and seedyield in forage sorghum. This research was carried out at Embrapa Maizeand Sorghum, in two seasons (2017 and 2018), in a randomized completeblock design, four replications and three varieties (BRS Ponta Negra, 1141574and 0947216) under application of Trinexapac-ethyl in two stages of the plantgrowth (V8, V12, V8 + V12). The characteristics evaluated were: plant height,seed yield and mass of 1000 seeds. The effect of the hormone was significantin both stages of growth, with a significant reduction in plant height. Thehormone applied twice at growth stages V8 + V12 had a greater effect inreducing plant height. However, the hormone reduced seed yield in the threevarieties, what implies the need for further studies comparing the advantageof plant height reduction and the loss in seed yield.

Performance of Chrysanthemum or Chrysanthemum Morifolium Ramat (CV. Balady) in Different Saline Water Irrigated Soils and Growing Media

As a result of the decreasing availability of high-quality irrigation water, the salinity tolerance of cut flowers is of increasing importance. The influence of salinity on the growth and quality of Chrysanthemum, Chrysanthemum morifolium L. grown in two different media under four salinity levels was evaluated. C. morifolium plants were grown in plastic pots containing either zeolitic tuff or soil as potting media. Seedlings of C. morifolium were subjected to four NaCl/CaCl2 salinity levels (2, 4, 6, and 8 dS.m-1). The effect of increasing salinity level on growth, flowering characteristics, time to flower, length and diameter of flowering shoots, and the diameter of the terminal flower on each stem were evaluated. On termination of the experiment, plant height, two perpendicular canopy widths, and fresh and dry weights of shoots were measured. Results indicated that most of all measured characteristics were reduced in response to increasing salinity levels. Increasing salinity levels caused significant reductions in plant height, fresh and dry yield, and relative water content. Moreover, salinity reduced flower quality (color, size, stem thickness, and length) and yield. Also, some physiological changes occur in stomatal conductance, leaf relative water content, and chlorophyll content. C. morifolium plants showed a good salinity resistance by irrigating plants with saline water up to 4 dS.m-1. Significant differences in C. morifolium plant responses were also detected between soil and zeolitic tuff media for most tested characteristics, in which using zeolitic tuff as rowing media was better to cope with higher salinity levels than plants grown in soil. In conclusion, it is recommended to use zeolitic tuff instead of soil when water salinity is a problem in irrigation water.

Response of wheat varieties to salinity: growth, yield and ion analysis

In plants, development, growth and yield most severely affected through saline soil/water in growth medium, ultimately cause severe threat to global food production for human being. Wheat (Triticum aestivum) is the most edible crop in Pakistan. Production of this crop can be improved through using marginal areas with the help of growing salt-tolerant varieties. The present investigation is carried out to screen out six local wheat varieties (F.Sarhad, Insaf, Lalma, Tatora, Bathoor and Barsat) with reference to their vegetative and reproductive growth, different physiological parameters [relative water content (RWC), electrolyte-leakage (EL) and leaf water loss (LWL)] and ionic status of plants. Present experiment designed in completely randomized manner (CRD) and 54 pots were arranged in the Botanical Garden, Department of Botany. These pots arranged in 6 lines with 9 pots/line and each line was irrigated with non-saline (control), 50 mM and 150 mM NaCl solution. The data from present research revealed that application of salt cause significant reduction in plant-height, root-length, fresh-biomass, dry-biomass, seed number/plant, seed weight/plant, spike-weight, relative water content, leaf water loss, and different ions of plants. Similarly at same applied doses of salt weight of 100 seeds, spike-length, electrolyte-leakage, Na+ and Cl- ions become increased. It has been concluded from the results of present study that varieties F. Sarhad, Insaf and Lalma exhibited more salt tolerance as compare to other varieties. So, these recommended for growing on moderately salt affected soil/water to achieve more yield of wheat from such affected lands of Khyber Pakhtunkhwa, Pakistan.