Reduction In Total Dry Weight Research Articles

Mechanism of salt tolerance in the endangered semi-mangrove plant Barringtonia racemosa: anatomical structure and photosynthetic and fluorescence characteristics.

To elucidate the mechanisms governing the salt tolerance of the endangered semi-mangrove plant Barringtonia racemosa, the biomass, photosynthetic and fluorescent characteristics, and anatomical structure of B. racemosa were studied under low, medium and high salt stress. The results showed that the stem dry weight, net photosynthetic rate, intercellular CO2 concentration, Fv/Fm, and ΦPSI of B. racemosa decreased under high salt stress, which led to a significant reduction in total dry weight. Stem dry weight was significantly positively correlated with the thickness of palisade tissue and significantly negatively correlated with the thickness of the epidermis of roots and xylem of stems. Therefore, a stable net photosynthetic rate and intercellular CO2 concentration, an increase in Fv/Fm and ΦPSI, an increase in or stable palisade tissue and spongy mesophyll of leaves and an increase in xylem thickness of the stem and epidermis, outer cortex, and stele diameter of roots could contribute to the salt tolerance of B. racemosa.

Dpp-mediated TGF-β signaling regulates vitellogenesis through 20-hydroxyecdysone signaling in the cabbage beetle, Colaphellus bowringi

The Dpp signaling, as one of the branches within the TGF-β superfamily, plays a crucial role in regulating various biological processes in insects. However, its impact on female reproduction through vitellogenesis remains unclear. In this study, the expression profiles implied that the Dpp signaling genes, including Dpp, Punt, Mad, and Medea, were up-regulated during reproductive development in the ovary of Colaphellus bowringi. Knockdown of these five Dpp signaling genes revealed significant effects of Dpp, Tkv, Mad, and Medea on ovarian development through vitellogenesis in the fat body. Our finding further indicated that Dpp signaling influences the expression of 20-hydroxyecdysone (20E) receptor and responsive genes in the fat body. Additionally, knockdown of 20E receptor EcR resulted in similar phenotypes as observed in the Dpp pathway genes knockdown, implying a regulatory role for Dpp signaling via EcR in vitellogenesis. Furthermore, knocking down Dpp, Tkv, and EcR in female adults led to a reduction in total dry weight and protein content, as well as the expression of mTOR, a factor linked to protein intake. These results suggest that the Dpp signaling pathway modulates vitellogenesis by impacting the AA/TOR-mediated 20E pathway in the fat body, providing novel insights into the network governing insect reproduction and offering potential targets for controlling female pest reproduction.

Nitrogen modulates early growth and physio-biochemical attributes in fragrant rice grown under cadmium and multiwall carbon nanotubes stresses.

Nitrogen (N) modulates plant growth, but its impact on the early growth and physio-biochemical characteristics of rice under cadmium (Cd) and multiwall carbon nanotubes (MWCNTs) toxicity has received little attention. In this study, a hydroponic experiment was conducted on two fragrant rice cultivars, e.g., Xiangyaxiangzhan (XYXZ) and Yuxiangyouzhan (YXYZ), grown under two N levels (N and 1/4N) and various Cd and MWCNTs treatments (CK: without CdCl2 or MWCNTs; Cd: 100μmol L-1 CdCl2; MWCNTs: 100mg L-1 MWCNTs; and Cd-MWCNTs: 100μmol L-1 CdCl2 + 100mg L-1 MWCNTs). Results showed that when compared to CK, the total dry weight of the Cd and MWCNTs treatments did not change under 1/4N for both varieties, whereas Cd and Cd-MWCNTs treatments resulted in a significant reduction in total dry weight by 18.78-37.85% for XYXZ and the Cd-MWCNTs treatment resulted in a significant reduction in the total dry weight by 20.24% for YXYZ. The changes in total dry weight were linked to changes in the dry weight of the different parts of the plant. Besides, the antioxidant parameters and the enzymes involved in the nitrogen metabolism changed in different varieties and different plant parts under two N levels and various Cd and MWCNTs treatments. In addition, differences in total dry weight changes at the N levels and various Cd and MWCNTs treatments were identified between the two varieties, and the relations between total dry weight and other investigated parameters indicated that the modulation processes varied between varieties. Overall, N modulates the early growth and physio-biochemical attributes in fragrant rice seedlings under Cd, MWCNTs, and their combined toxicity.

Ion-specific Limitations of Sodium Chloride and Calcium Chloride on Growth, Nutrient Uptake, and Mycorrhizal Colonization in Northern and Southern Highbush Blueberry

Excess salinity is becoming a prevalent problem for production of highbush blueberry (Vaccinium L. section Cyanococcus Gray), but information on how and when it affects the plants is needed. Two experiments, including one on the northern highbush (Vaccinium corymbosum L.) cultivar, Bluecrop, and another on the southern highbush (V. corymbosum interspecific hybrid) cultivar, Springhigh, were conducted to investigate their response to salinity and assess whether any suppression in growth was ion specific or due primarily to osmotic stress. In both cases, the plants were grown in soilless media (calcined clay) and fertigated using a complete nutrient solution containing four levels of salinity [none (control), low (0.7–1.3 mmol·d−1), medium (1.4–3.4 mmol·d−1), and high (2.8–6.7 mmol·d−1)] from either NaCl or CaCl2. Drainage was minimized in each treatment except for periodic determination of electrical conductivity (EC) using the pour-through method, which, depending on the experiment, reached levels as high as 3.2 to 6.3 dS·m−1 with NaCl and 7.8 to 9.5 dS·m−1 with CaCl2. Total dry weight of the plants was negatively correlated to EC and, depending on source and duration of the salinity treatment, decreased linearly at a rate of 1.6 to 7.4 g·dS−1·m−1 in ‘Bluecrop’ and 0.4 to 12.5 g·dS−1·m−1 in ‘Springhigh’. Reductions in total dry weight were initially similar between the two salinity sources; however, by the end of the study, which occurred at 125 days in ‘Bluecrop’ and at 111 days in ‘Springhigh’, dry weight declined more so with NaCl than with CaCl2 in each part of the plant, including in the leaves, stems, and roots. The percentage of root length colonized by mycorrhizal fungi also declined with increasing levels of salinity in Bluecrop and was lower in both cultivars when the plants were treated with NaCl than with CaCl2. However, leaf damage, which included tip burn and marginal necrosis, was greater with CaCl2 than with NaCl. In general, CaCl2 had no effect on uptake or concentration of Na in the plant tissues, whereas NaCl reduced Ca uptake in both cultivars and reduced the concentration of Ca in the leaves and stems of Bluecrop and in each part of the plant in Springhigh. Salinity from NaCl also resulted in higher concentrations of Cl and lower concentrations of K in the plant tissues than CaCl2 in both cultivars. The concentration of other nutrients in the plants, including N, P, Mg, S, B, Cu, Fe, Mn, and Zn, was also affected by salinity, but in most cases, the response was similar between the two salts. These results point to ion-specific effects of different salts on the plants and indicate that source is an important consideration when managing salinity in highbush blueberry.

Effect of Asynchronous Light and Temperature Fluctuations on Plant Traits in Indoor Growth Facilities

Several studies have recommended the incorporation of environmental fluctuations in indoor experiments if closer-to-natural results in plant experiments are desired. Previous authors have suggested that if these fluctuations are not applied in synchrony, a stress effect could be present since plants have evolved to cope with synchronic environmental fluctuations. This study aimed to identify the effect of disparity in fluctuations of two important environmental variables, light quantity and temperature, on the growth of seven plant species from different functional plant types. A full-factorial combination of light and temperature under fixed or variable conditions was applied in phytotrons, and plant performance under these conditions was compared with a previous field trial. In all phytotron treatments, the average light and temperature conditions were the same as in the initial field trial. Productivity, leaf gas exchange, chlorophyll fluorescence, pigmentation, and other leaf traits were recorded in all species at the end of the experiments. Most plant trait responses were highly dependent on species and treatment, but some general trends were observed. Light fluctuations were mainly responsible for increases in specific leaf area (SLA) and chlorophyll a concentration, as well as for reductions in total dry weight and chlorophyll a/b ratio, independent if in combination with fluctuation or fixed temperatures. When fixed light conditions were combined with variable temperatures, the plants showed on average lower Fv/Fm values, Amax, and CO2 yield, while under variable light conditions and fixed temperatures, Fv/Fm increased compared with fully fixed or variable conditions. Although significant differences of plant traits between the field trial and all phytotron treatments were present (likely due to differences in other parameters that were not controlled in the phytotrons), our results still suggest that a synchronous variation of environmental factors lead to a more natural-like plant growth than if these factors are fixed or vary asynchronously.

Responses of plant growth, physiological, gas exchange parameters of super and non-super rice to rhizosphere temperature at the tillering stage

Temperature is one of the critical factors affecting rice growth and yield production. This study investigated the effects of rhizosphere temperature at the tillering stage on the growth, physiological parameters and gas exchange attributes of two rice cultivars, i.e., the super rice cultivar Yuxiangyouzhan and the non-super rice cultivar Xiangyaxiangzhan, under hydroponic conditions. Three rhizosphere temperature treatments, i.e., a low-rhizosphere-temperature treatment (LT, nutrient solution at 17.5 ± 1.5 °C), an ambient-temperature treatment (AT, nutrient solution at 27.5 ± 1.5 °C), and a high-rhizosphere-temperature treatment (HT, nutrient solution at 37.5 ± 1.5 °C), were applied in this study. The results showed significant differences in most of the rice growth and physiological and gas exchange parameters as a result of cultivar and rhizosphere temperature as well as their interaction. In addition, the marked reduction in total dry weight was positively correlated with a notable reduction in plant morphological parameters, such as the fresh and dry weight of the leaves and stem sheaths, and changes in gas exchange parameters. Moreover, antioxidant reactions were active in response to high and low rhizosphere temperatures, which varied in different plant tissues. These results suggested that the super and non-super rice were sensitive to high and low rhizosphere temperatures, respectively.

Effect of planting methods and weed management practices on yield of green gram {Vigna radiata (L.) R. Wilczek}, weed dynamics vis a vis phytotoxicity in green gram

An experiment was carried out to find out suitable method of planting and weed management in green gram grown during the kharif season of 2014 and 2015. The density of E. colona and C. rotundus was significantly reduced in raised bed planting method. Significant reduction in total dry weight of weeds was obtained in raised bed planting method as compared to conventional and zero till planting method. Maximum weed control efficiency was found in raised bed planting method. Significantly more number of seeds pod-1 were observed in raised bed planting method as compared to conventional and zero till planting method. Seed yield and straw yield were found maximum in raised bed planting method during both years of study and were statistically at par in conventional and zero till planting method. Harvest index was not influenced by planting methods. Phytotoxicity on crop due to different herbicides was similar under different planting methods. Among different weed management treatments, HW at 15 and 30 DAS was found most effective in reducing density and dry weight of weeds during crop growing period except at 15 DAS (where weeding was done after taking observation). Maximum weed control efficiency was observed in HW (15 and 30 DAS). Weedy check treatment resulted in minimum while weed free treatment resulted in maximum number of seeds pod-1. Among the treatments having herbicide application, post emergence application of Imazethapyr @ 100 g ha-1 resulted in maximum seed and stover yield.

Effect of the foliar enrichment and herbicides on maize and associated weeds irrigated with drainage water

A two-year field experiment was conducted during summer seasons of 2013 and 2014, which were irrigated by drainage water which belong to salinity class (C3S1 to C4S2), to study the effect of the foliar enrichment namely (Anti-stress) and weed management treatments (some pre and post-emergence herbicides and two-hand hoeing) on maize growth, yield, yield components and chemical composition of maize grains and associated weeds (Portulaca oleracea, Amaranthus retroflexus and Echinochloa colonum). The results illustrated that application of the foliar enrichment enhanced the dry weight of weeds and increased maize growth characters, yield and yield components and total crude protein and total oil percentage of grain maize, as compared with untreated treatment. All weed management treatments caused a significant reduction in total dry weight of weeds at 60 and 80 days after sowing in both seasons. Two-hand hoeing treatment exerted the highest decrease in total dry weight of weeds followed by metribuzin, oxadiagyl, fluroxypyr and bentazon, respectively at 60 and 80 days after sowing compared with other weed management treatments. While, the highest values of maize growth, yield, yield components and maize grains' content of protein and oil was obtained with two-hand hoeing followed by metribuzin, oxadiagyl, fluroxypyr and bentazon, respectively. While, two hands hoeing produced the maximum values of leaf area, ear length, the weight of kernels plant−1, but applying of metribuzin treatment gave the highest values of total oil percentage of grain maize when the foliar enrichment was used.

Evaluation of morphological characteristics of local and improved rice (Oryza sativa L.) genotypes under two nitrogen levels in hydroponic culture

In order to study the response of rice genotypes to different levels of nitrogen (N), an experiment was conducted to evaluate growth and development of 28 selected rice genotypes (improved and local from north of Iran, and cultivated in Central Iran) under two levels of N including 2.85 mM (N concentration of Yoshida solution) and 1.42 mM (half the N concentration of Yoshida solution) from ammonium nitrate source. The experiment was arranged as factorial, based on a completely randomized blocks design, with three replications. Results showed that the effects of genotype, N level and their interaction were significant on the number of tillers, leaf area, SPAD index, dry weight of roots, shoot and total, shoot and root length and biomass. The extent of reductions in the values of all measured traits, except for root length and dry weight, were higher in north local genotypes as compared to other tested groups. The reductions in total dry weight were 14.82, 5.80 and 2.67 percent for north local, north improved and genotypes from center of Iran, respectively. There was significant variation among genotypes in response to nitrogen deficiency. Nitrogen efficiency was highest in Fajr and Khazar within north improved genotypes, in Hassani and Kazemi within north local genotypes and in Line2 Firozan within genotypes from center of Iran. However, the lowest values for nitrogen efficiency were achieved in Nemat and Shirodi within north improved genotypes, in Tarom-mantaghe and Ahlami Tarom within north local genotypes and in Zayandehrud within genotypes from center of Iran. Results showed that correlation between shoot dry weight (as plant yield) with number of tillers and plant leaf area were higher under N deficiency (r= 0.74 and r= 0.57) than under nitrogen sufficiency (r = 0.13 and r = 0.41) conditions.

Performance of Herbicides in Black Gram(Vigna MungoL.) and Associated Weed Flora

A field experiment was conducted during 2014 and 2015. To evaluate the effect of weed management practices on weed flora, weed dry weight, yield attributes and yield of blackgram (Vigna mungo L.). All the weed species were controlled effectively by the application of herbicides. Among the herbicides with the application of Pendimethalin 900 g ha-1 as pre - emergence + one hand weeding recorded minimum total dry weight in weeds and maximum grain yield of blackgram. The reduction in total dry weight (25.4 g m-2) and maximum yield was found in hand weeding at 20 and 40 DAS. However Pendimethalin 900 g ha-1 Pre-emergence+ one hand weeding and Imazethapy + Pendimethalin (Pre-emergence) was found at par with two hand weeding.

Herbicidal Activity of Penoxsulam And Bispyribac-Sodium and its Combination With Mineral Oil And Spreading Material on Weed Rice Plant

Two field experiments were carried out at the Experimental Farm of Rice Research and Training Center(RRTC), Sakha, Kafr El-sheikh, Egypt, during 2009 and 2010 rice growing seasons. to study the effect of certain postemergenceherbicides (Penoxsulam and Bispyribac-sodium and their mixtures with mineral oil KZ and spreadingmaterial (Top film) on weeds control rice plant compared with non-chemical control Weedy check, The results Theresult showed that the number of tiller to Echinochloa crus-galli , Echinochloa colonum , Cyperus difformis. In alltested treatment from the results the most lesser above of weeds and highest percent reduction of weeds was found inpenoxsulam and bispyribac-sodium at the recommended rate of each herbicides wean the half rate both compounds wascompared one litter of spreading material or one litter of mineral oil was slightly increased of weeds with the higherincrease of percent reduction in total weeds compared with the effect of the half rate only of each tested compound.penoxsulam 2.5% half rate + 1000ml spreading material which gives 82%, 87%,83% and 84%,92%,88% during2009and 2010 season respectively. bispyribac-sodium 2% half rate + 1000ml spreading material which gives89%,89%,89% and 88%, 94%, 87% reduction in the total number, Also gave the most highest percent reduction in totaldry weight of weeds. When the mineral oil and spreading material were used with half recommended rate of the twoabove herbicides the percent reduction of dry weight of weed were approximately equal to the recommended rate ofeach tested herbicides such effect relieved to the efficacy of mineral oil and spreading material to improve the power ofhalf rate to reach the effect of recommended rate.

Effects of the ectomycorrhizal fungus Pisolithus tinctorius and Cd on physiological properties and Cd uptake by hybrid poplar Populus alba × glandulosa

The effects of the ectomycorrhizal fungus Pisolithus tinctorius and cadmium (Cd) on physiological properties and Cd uptake by Populus alba <TEX>${\times}$</TEX> glandulosa was investigated under greenhouse conditions. Cd treatment decreased the photosynthetic rate (<TEX>$P_N$</TEX>) of both non-mycorrhizal (NM) plants (16.3%) and ectomycorrhizal (ECM) plants (11.5%). In addition, the reduction in total dry weight by Cd treatment was greater in ECM plants (24.3%) than that in NM plants (17.6%). Mycorrhizal infection increased the <TEX>$P_N$</TEX> and transpiration rate in both control and Cd-treated plants. Cd treatment increased superoxide dismutase (SOD) activity and decreased glutathione reductase activity, and the increase of SOD activity by Cd treatment was greater in NM plants (40.3%) than that in ECM plants (3.7%). Thiol content increased in both NM and ECM plants treated with Cd solution, and the increase in thiol content in NM plants (43.9%) was greater than that of ECM plants (15.6%). Cd uptake in the leaves, stems, and roots of ECM plants was 69.9%, 167.2% and 72.8%, respectively, higher than in the NM plants. However, the increase in Cd uptake ability of ECM plants resulted in a reduction in dry weight.

Effects of water deficit stress on growth, water relations and osmolyte accumulation in Medicago truncatula and M. laciniata populations

The effects of water stress were investigated in two Tunisian Medicago truncatula populations collected from arid (Mt-173) and sub-humid (Mt-664) climates and two Tunisian M. laciniata populations originating from arid (Ml-173) and semi-arid (Ml-345) regions. After a pre-treatment phase (24 days after sowing, DAS) of watering at 100% of field capacity (FC), the plants were either irrigated at 100% FC or at only 33% FC. After 12 days of treatment (36 DAS), one lot of dehydrated plants was rewatered at 100% FC. A final harvest was carried out after 24 days of treatment (48 DAS). Measured parameters were total dry weight (TDW), root shoot ratio (RSR), leaf relative water content (RWC), osmotic potential (OP), photosynthetic parameters (CO 2 net assimilation A, stomatal conductance g s and transpiration E), malondialdehyde (MDA) concentration and leaf contents in inorganic (Na + and K +) and organic solutes (proline and soluble sugars). Under water deficit conditions, compared to M. laciniata, M. truncatula populations showed a higher reduction in TDW, A, g s and RWC associated with a higher increase in MDA concentration. Thus, the relative tolerance of M. laciniata populations to water shortage would be related to their lower intrinsic growth rate and stomatal control of gas exchange. TDW, A, g s , E and RWC were more decreased by water deficit in Ml-345 than in Ml-173. Drought tolerance of Ml-173 was found to be associated with a more pronounced decrease of OP and a lower reduction in RWC due to the accumulation of solutes such as proline, soluble sugars and K +. In addition, Ml-173 showed the highest water use efficiency values (WUE) and the lowest MDA concentrations under water deficit stress.

Responses of ‘Petopride’ processing tomato to partial rootzone drying at different phenological stages

Partial rootzone drying (PRD) is a water-saving irrigation practice which involves watering only part of the rhizosphere at each irrigation with the complement left to dry to a pre-determined level. The effect of PRD, applied at different phenological stages, on yield, fruit growth, and quality of the processing tomato cv. ‘Petopride’ was studied in this experiment. The treatments were: daily full irrigation (FI) on both sides of the root system considered as the control, and PRD treatments applied at three phenological stages. These were: during the vegetative stage until the first truss was observed (PRDVS–FT), from the first truss to fruit set (PRDFT–FS), and from fruit set to harvest (PRDFS–H). In some occasions, leaf xylem water potential was lower in each PRD period than in FI. Number of fruits, total fresh and dry weight of fruit per plant, harvest index, and fruit growth were lower in PRDFT–FS and PRDFS–H plants than in FI and PRDVS–FT plants. However, irrigation water use efficiency, on a dry weight basis, was the same among the treatments. For PRDFT–FS and PRDFS–H treatments, mean fresh weight of fruit and fruit water content were reduced and dry matter concentration of cortex and total soluble solids concentration of fruit increased compared with FI and PRDVS–FT treatments. Incidence of blossom-end rot was the same among PRDVS–FT, PRDFS–FH, and FI fruit, but it was higher in PRDFT–FS fruit. Fruit skin colour was the same among treatments. Total dry weight of fruit per plant decreased by 23% for PRDFT–FS and by 20% for PRDFS–H relative to FI. Fruit quality improvement in PRDFS–H could compensate for the reduction in total dry weight of fruit where water is expensive for tomato production. But an economical analysis would be needed to substantiate this. PRD from the first truss to fruit set is not recommended because of the high incidence of blossom-end rot.

Development of a process for the production of nutrient supplements for fermentations based on fungal autolysis

This study verifies the potential of fungal autolysis as an alternative process for the production of nutrient-rich solutions similar to yeast extracts. Autolytic experiments were carried out on fermentation solids derived from either batch or continuous submerged cultivations of Aspergillus awamori on various wheat flour milling streams. The degree of autolysis was not affected by the pH range used (3–6.5), whereas it was severely affected by temperature (30–55 °C), initial solids concentration (10–45 g/L) and incubation time. The enzymatic disruption of the fungal cell wall was identified by image analysis as well as by the reduction in total dry weight and the gradual release of various components, such as free amino nitrogen and phosphorus. The novel method of autolysate recycling enabled the enrichment of the solution with lytic enzymes leading to increased fungal cell degradation rates. In this way, it was made possible to reduce the initial total dry weight by 47% and produce a nutrient-rich solution containing 1.6 g/L free amino nitrogen, 5.3 g/L total nitrogen and 0.5 g/L phosphorus.

Turf and Ornamental Plant Tolerances to Endothall in Irrigation Water II. Turf Species

Two formulations of the contact herbicide endothall are used to control submersed aquatic weeds. Waters treated with the amine or dipotassium salt formulations have irrigation restrictions varying from 7 to 25 days depending on the concentration of endothall applied. These water-use restrictions may be reduced for turfgrass if studies conclude there is no phytotoxicity to turf species irrigated with concentrations of endothall that may exist after an aquatic application. Two separate experiments were conducted to determine turfgrass tolerance to endothall in irrigation water on five species of grass: annual ryegrass (Lolium multiflorum), annual bluegrass (Poa annua), centipedegrass (Eremochloa ophiuroides), `Floratam' st. augustinegrass (Stenotaphrum secundatum), and `Tifton 419' bermudagrass (Cynodon dactylon). Expt. 1 used constant concentrations of endothall; Expt. 2 used decreasing concentrations of endothall over time. Annual turf species (bluegrass and ryegrass) were generally more susceptible than perennial turfgrasses. Concentrations resulting in a 10% reduction in total dry weight harvested compared to control plants [effective concentration (EC10)] for the amine and dipotassium salt formulations were 10 and 14 mg·L–1 (ppm) a.i. on annual ryegrass, 10 and 16 mg·L–1 a.i. on annual bluegrass, 50 and 54 mg·L–1 a.i. on centipedegrass, 47 and 72 mg·L–1 a.i. for st. augustinegrass, and for bermudagrass 1301 and 908 mg·L–1 a.i. in Expt. 1. Expt. 2 resulted in EC10 values of 31 and 35 mg·L–1 a.i. on annual ryegrass, 7 and 12 mg·L–1 a.i. on annual bluegrass, 32 and 99 mg·L–1 a.i. on centipedegrass, 27 and 20 mg·L–1 a.i. on st. augustinegrass for the amine and dipotassium formulations of endothall respectively, and 958 mg·L–1 a.i. for the dipotassium formulation on bermudagrass. There was no effect on bermudagrass dry weights when exposed to the amine formulation of endothall in Expt. 2 at concentrations up to 1600 mg·L–1 a.i. There is a low risk of inhibiting growth of turf species at endothall concentrations used for aquatic weed control considering the maximum use concentrations, typical uses of the products, and decomposition rates.

INFLUENCE OF WATER SALINITY ON GROWTH AND WATER RELATIONS OF LOQUAT PLANTS GRAFTED ON TWO ROOTSTOCKS

The experiment was performed on two-year-old loquat “Algerie” trees (Eriobotrya japonica Lindl.) grafted on Franco and Anger rootstocks, growing in a glasshouse under partially controlled conditions. Trees were submitted to five saline treatments for 5 months: 5 (control), 25, 35, 50 and 70 mM NaCl in nutrient solutions. At the end of the experiment, plant biomass, leaf Na and Cl concentrations, photosynthesis rate and various water relations parameters from both scion-rootstock combinations were measured and evaluated. The total dry weight of loquat plants on Anger rootstock was unaffected by salinity, whereas those grafted on Franco, a significant reduction in total dry weight was noted. Loquat trees grafted onto Franco treated with 50mM and 70mM NaCl caused a substantial degree of defoliation and foliar necrosis. Plants grafted onto Anger showed lower Na + concentrations in leaves than those grafted onto Franco, demonstrating that it is an efficient Na + excluder. Under low salinity levels the accumulation of Cl - in both rootstock-scion combinations was similar. Sodium had a more adverse effect than chloride on the dry weight. The reduction in photosynthesis level was more marked on plants grafted on Franco. Lower leaf water potential values were observed in plants grafted on Franco than those grafted on Anger at moderate salinity levels. Osmotic adjustment permitted the maintenance of leaf turgor in treated plants grafted on Anger, but did not prevent a decrease in leaf turgor in Franco.

Differential Growth, Quality and Nutrient Responses of Azalea Hybrids to Salinity

The azalea hybrids `Delaware Valley White' (`DVW') and `Hershey Red' (`HR') were grown in 7-L containers filled with a 4 sphagnum peat: 2 pine bark: 1 sand medium (v/v) and fertigated for 15 weeks with a complete nutrient solution supplemented with 0, 6 and 12 mm NaCl-CaCl2 (2:1 molar ratio). Regardless of salinity stress, `DVW' plants had dry weights and leaf areas significantly higher (by 24.7% and 10.2%, respectively) than in `HR' plants. Salinity, however, caused differential growth and quality responses between the hybrids. Growth in `DVW' plants decreased with salinity increases, with 22.6% and 32.4% reductions in total dry weight and leaf area, respectively, observed at 12 mm salt compared to controls. Conversely, `HR' plants exposed to 12 mm salt showed no differences in yield parameters with respect to the controls, whereas plants receiving 6 mm salt showed increases of 14.0% and 7.1% in total dry weight and leaf area, respectively, with respect to the controls. Plant quality, as assessed by visual symptoms of salt injury (“salt burn”), was significantly reduced by salinity increases in `DVW' plants, but was not affected in `HR' plants. While unaffected by salinity, leaf K status in `HR' plants was significantly lower than in `DVW', which showed increases in K concentration with salinity increases. Leaf Ca, Cl and Na concentrations increased with added salinity in both hybrids. The `DVW' plants, however, accumulated exceedingly higher Cl and Na concentrations (up to 3.33% and 5,650 mg·L-1 respectively) than in `HR' plants (up to 1.31% and 463 mg·L-1, respectively). Only the yield and quality of `DVW' plants were negatively and significantly correlated to increases in leaf Cl and Na concentrations.

Salinity Tolerance in Phaseolus Species during Early Vegetative Growth

ABSTRACTThe genus Phaseolus includes important cultivated species as well as wild species with diverse ecological adaptations. Characterization of the ecological adaptations of the wild species would be useful for improved understanding, conservation, and utilization of these genetic resources. Salinity tolerance during vegetative growth was evaluated for 132 accessions for 14 wild Phaseolus species (P. acutifolius A. Gray, P. angustissimus A. Gray, P. carteri Freytag &amp; Debouck, P. filiformis Bentham, P. glabellus Piper, P. leptostachyus Bentham, P. lunatus L., P. micranthus Hook &amp; Arnold, P. microcarpus Mart, P. mcvaughii A. Delgado, P. oligospermus Piper, and P. vulgaris L.) and 11 accessions representing five cultivated species (P. acutifolius, P. coccineus L., P. lunatus L., P. polyanthus Greenman, and P. vulgaris) in nutrient solution containing 0 and 180 m M sodium chloride for 21 d. When plants were salinized after the emergence of the first trifoliate leaf, wild accessions of P. acutifolius, P. filiformis, P. lunatus, and P. vulgaris showed a wide range of variation in their salinity tolerance as defined by total dry weight reduction (PR) as a percentage of the unsalinized controls, salt susceptibility index (SSI), and root: shoot ratio (RSR). SSI and PR were correlated positively, indicating either trait could be used to select salt‐tolerant accessions. Cluster analysis revealed substantial intraspecific and interspecific variation in salinity tolerance. Salinity tolerance was observed in wild P. micranthus, P. mcvaughii, P. lunatus, cultivated P. coccineus, and several accessions of wild P. filiformis, and P. vulgaris Of these, P. filiformis was noteworthy in having 9 of 11 accessions rated as highly tolerant. Wild P. vulgaris was more salinity tolerant than the three cultivated P. vulgaris accessions included in the study. Many tolerant accessions originated in arid, coastal, or saline areas. We conclude that the genus Phaseolus has substantial diversity in salinity tolerance.

EFFECTS OF pH ON GROWTH AND NODULATION OF TWO FORAGE LEGUMES

A study was conducted to compare the responses to acid pH of Medicago sativa and Lotus glaber, two forage legumes with different environmental requirements, either supplied with inorganic nitrogen (N) or inoculated with different strains of their nodule bacteria. Medicago sativa showed, in both treatments, a significant reduction in total dry weight at pH below 6.0. In contrast, Lotus glaber grew equally well at all the pHs assayed in the presence of adequate N. Under inoculated conditions, in the absence of N supply, plant growth was dependent on the bacterial strain used. When the ability of each strain to multiply in culture medium was examined, it was observed that Sinorhizobium meliloti strains showed a pH-sensitive response that inhibited growth at pH 4.0, whereas Mesorhizobium loti strains showed normal growth at this pH. These results suggest that for the effectiveness of Mesorhizobium loti–Lotus glaber symbiosis in acid soils the major factor to be considered is the tolerance of the bacterial strain to acid conditions, while the limiting factors for the Sinorhizobium meliloti–Medicago sativa symbiosis are the sensitivity to low pH of both the plant and its bacteria.