The Effect of Short Warm Breaks during Chilling on Water Status, Intensity of Photosynthesis of Maize Seedlings and Final Grain Yield

The effects of short-term exposure of seedlings to suboptimal temperature (14 °C for 1 or 4 h in 24 h cycles) during chilling (5 °C for 12 days) on the water status and intensity of photosynthesis of tolerant (TG) and chilling-sensitive (SG) maize genotypes were studied. Daily warming for 1 or 4 h resulted in a decrease in the hydration of the seedlings to 31.1 % and 61.5 % (SG) and 14.8 % (TG) and 39.1 % (SG), respectively, in comparison with the continuously chilled control. During warming for 4 h, both genotypes absorbed water from soil in amounts that partly compensated for its loss through transpiration, after the plants had been moved to the lower temperature. A protective effect of shorter warming (1 h) on the hydration of the seedlings was a result of a strong, stomatal limitation of transpiration during the initial days of chilling. Warming for 1 or 4 h also increased the ability of TG stomata to close in reaction to water deficit in chilling conditions. The effect of increased temperature delayed the decrease of P_N in leaves and limited RGR inhibition of the seedling mass caused by chilling. Daily warming of plants at the seedling phase (14 and 20 °C for 1 or 4 h) reduced the unfavourable effect of chilling (5 °C for a period of 8 days) on the final yield, the filling of caryopses and their number in a cob after growth in natural conditions.     

The Effect of Short Warm Breaks during Chilling on Photosynthesis and the Activity of Antioxidant Enzymes in Plants Sensitive to Chilling

The effect of short warm breaks (from 15 min to 5 h) during chilling of three chilling-sensitive species (tomato, maize and soybean) was investigated. Injuries, intensity of net photosynthesis and antioxidant enzyme activity were measured. Throughout chilling treatment, plants were warmed by transferring them during the last few hours of the light phase from chilling temperature (5 °C for tomato and maize, 2 °C for soybean) to 20 °C. After warming, seedlings were moved back to chilling conditions. Warm breaks of 5 h almost entirely prevented the appearance of injuries, as measured by changes in leakage of electrolytes and tissue water content, during 12 days of chilling. Even a 15-min warm break ensured a significant decrease in injuries in chilled maize seedlings compared to continuously chilled seedlings. Inhibition of gas exchange and fluorescence in seedlings of two maize genotypes differing in chilling resistance was, to a small extent, prevented by 1-h warm breaks, while 4-h warm breaks reduced inhibition significantly. The length of the warm break (1 or 4 h) had no influence on changes in SOD activity compared to continuously chilled plants, but warm breaks of 4 h produced a significant increase in CAT activity. The possible influence of an alternative pathway in preventing injuries is discussed.     

Effect of Low Night Temperatures on Photosynthetic Activity of the Maize Seedlings (Zea mays L.)

Night chilling (5 °C) subsequently lowered photosynthetic intensity in the leaves of maize seedlings at 20 °C through an increase in leaf diffusive resistance brought on by lower tissue water content in morning hours. A more significant increase in leaf diffusion resistance was observed when soil temperature was lowered than in the case of lower air temperature.
The unfavorable effect of soil and air cooling temperature on photosynthesis was limited by air saturated with water vapour. However, as a result of lowering the night temperature from 5 °C to 1 °C, the efficiency of the protective influence of higher atmospheric humidity was decreased. This demonstrates that the participation of factors unrelated to plant water status in inhibiting photosynthesis increases with lower night temperatures.
An additional reason for inhibited photosynthesis following cool nights was a decrease in chlorophyll accumulation, below 50 μg per 1 cm² of leaf area.     

Changes in Leaf Water Relations and Injuries in Maize Seedlings Induced by Different Chilling Conditions

The time course of injuries and electrolyte leakage as well as changes in leaf water content and relative turgidity during chilling at 5°C, 65 or 100 % relative humidity (RH) were determined for seedlings of two maize hybrids differing in chilling tolerance.
In the course of chilling of entire seedlings the statistically significant injuries and increased leakage of electrolytes occurred first, followed by significant water deficit in leaves which was independent of RH and genotype. However, during prolonged chilling high and significant correlation between the level of chilling-induced water stress and the extent of injuries was observed. Thus it has been assumed that the main factor responsible for primary chilling injuries in maize seedlings is the immediate influence of chilling temperatures on the cell membranes, and not the secondary water stress. The level of the water stress and the extent of the dehydration injuries under chilling conditions depended on the chilling sensitivity of the genotype. Differences between the examined genotypes consisted not only in delayed chilling injuries in a chilling tolerant hybrid, but also in significantly lesser effects of these injures on water relations.
However, exposure to low temperature of the aboveground part or of the roots of the seedlings only, caused first the chilling-induced marked water deficit in the leaves and next increased leakage of electrolytes. A direct effect of chilling temperature on the membranes in a situation when only a part of the seedling is being chilled, may be less harmful to the plant as a whole owing to normal functioning of the non-chilled part.     

Electrolyte Leakage, ATP Content in Leaves and Intensity of Net Photosynthesis in Maize Seedlings at Permanent or Different Daily Exposure to Low Temperatures

Changes were determined in electrolyte leakage (EL), ATP content in leaves and intensity of net photosynthesis (FJ in maize seedlings as a result of continued exposure to low temperatures for several days or, after a cold night (5 °C, 9 h), alternating application of 5 °C and 20 °C temperatures during the lit phase of the day (h of chilling during day/night: 0/9, 5/9, 10/9, 15/9).
At continuous exposure to low temperatures, permanent reduction of ATP content occurred between days 7 and 10, while EL increased significantly between days 4 to 7 (depending on experimental conditions). Of three leaves differing in age, most injuries were found in the oldest leaf. An increased intensity of irradiation from 150 to 500 μE. m⁻².s⁻¹ caused an earlier decrease in the ATP content and a further increase in electrolyte leakage. ATP content showed a 24 h rhythm, it increased at the end of the night and decreased at the end of the day. The rhythm was particularly noticeable in the control plants (20 °C), as well as, however to a lesser extent, in plants exposed to daily fluctuating chilling temperatures. It has also been observed that higher temperatures occurring in day time may diminish electrolyte leakage induced by previous low temperatures
The intensity of F_n determined at 20 °C, 4 h after withdrawal of chilling, decreased with the prolongation of the chilling period during the day.
Thus, it may be assumed that the EL and F_n values as indicators of the plants' sensitivity are in better agreement with the induced chill doses than the ATP content in leaves, which to a greater extent depends on the interaction between chilling and other experimental factors, such as irradiation intensity or the sequence of light and darkness.     

Effects of Stem-Injected Plant Growth Regulators, with or without Sucrose, on Grain Production, Biomass and Photosynthetic Activity of Field-Grown Corn Plants

Study of plant growth regulators (PGRs) through conventional foliar application or tissue culture or other organic materials has limitations. No previous study has examined the effects of long-term continuous addition of PGRs, with or without sucrose, to field-grown corn ( Zea mays L.) plants. A field study was conducted to determine the effects on corn plant growth and productivity during the grain-filling period of a continuous supply of PGRs, with or without sucrose, using a recently developed injection technique to deliver pressurized solutions through syringe needles sealed to the stem with latex. Our four PGRs (IAA, ABA, ethephon and salicylic acid) and a distilled water control, and two levels of sucrose (150 g l⁻¹ and a distilled water control) were injected into corn plants for 42 consecutive days during the grain-filling period. The plants injected with solutions not containing sucrose took up 42 ml more than those injected with sucrose-containing solutions. Corn plants injected with salicylic acid (SA) produced 9 % more grain yield than plants injected with no PGRs. The combination of SA and sucrose increased the photosynthetic rate by 42 % when compared with distilled water. Injection of ethephon resulted in an 11 % reduction in grain yield. Neither IAA nor ABA altered plant photosynthesis or productivity. Sucrose injection increased the dry weight of injected internodes and stover, and induced partial stomatal closure, although without any measurable effect on net photosynthetic rate. This study showed that stem injection makes possible the study of changes in plant physiology during grain-filling due to the effects of PGRs and metabolites administered continuously over protracted periods of time. It also demonstrated a previously undocumented stimulation of plant photosynthesis and grain yield by SA.     

Effect of Temperature and Photoperiod on the Development of Lupinus albus L. in a Controlled Environment

An experiment to determine the effect of temperature and photoperiod on Lupinus albus under controlled environmental conditions was carried out, using the three Lupinus albus genotypes 'Tifwhite', 'Esta' and 'Kiev', and three temperature (10/20, 18/28 and 20 °C continuously) and two photoperiod (8 and 16 h daylength) regimes, in all combinations. Half of the seeds were vernalized for 21 days at 4 °C to alleviate the obligate vernalization requirement of Tifwhite. Although Esta and Kiev do not have obligate vernalization requirements, they were influenced by this vernalization period. Observations included the duration of the period from planting to seedling emergence, the duration of the period from planting to the beginning of flowering and the duration of flowering. The vernalization treatment accelerated plant development in all genotypes. The period from planting to emergence was shorter under the higher temperature regime. For all genotypes, the period from planting to flowering was shorter under the longer photoperiod, the same trend as would be expected for long-day plants. Duration of flowering periods were, in contrast to pre-flowering periods, shorter for all genotypes at cooler temperatures. The results of this study confirm that photoperiod does contribute to the growth period from planting to flowering in L. albus and that this species does behave as a long-day plant.     

脱落酸对低温胁迫下玉米幼苗生长和光合特性的影响

脱落酸（ABA）是作物生产中广泛应用的一种植物激素。探究ABA对低温胁迫下玉米幼苗光合特性的影响,为阐明低温胁迫下玉米幼苗叶片光合结构的防御保护机制提供理论依据。以玉米品种“久龙5号”为试验材料,采用盆栽试验,探讨了低温胁迫0、2、4、6、8d下不同浓度脱落酸对玉米幼苗生长及光合特性的影响。结果表明,低温胁迫显著抑制玉米幼苗的正常生长,导致SPAD值下降,叶片净光合速率（P_n）、蒸腾速率（T_r）、气孔导度（G_s）、PSⅡ光化学最大效率（F_v/F_m）和潜在光化学效率（F_v/F_o）水平下降,初始荧光（F_o）显著升高。外源喷施适当浓度的ABA能够显著缓解由低温胁迫导致的玉米叶片P_n、T_r和G_s下降幅度,提高F_v/F_m和F_v/F_o,降低F_o水平。由此可见,外源施加适当浓度的ABA能提高幼苗叶片的光合能力,提高PSⅡ反应中心活性,促进物质积累,提高玉米幼苗的耐冷性。同时,外源施加ABA存在一定的浓度效应,即“低促高抑”。本研究所设计浓度范围中15mg/L ABA浓度对光合抑制缓解效果最显著。     

Chilling Tolerance of 10 Maize Genotypes as Related to Chilling-induced Changes in ACC and MACC Contents

We studied chilling-induced changes of 1-aminocydopropane-1-carboxylic acid (ACC) and of 1-(malonylamino) cyclopropane-1-carboxylic acid (MACC) contents in seedlings of ten maize genotypes with different chilling tolerance. Seedlings at the third leaf stage were chilled at 5°C and at 65% RH. Immediately before and after two and five days of chilling the contents of ACC and of MACC in the third leaf were measured. Water content and – after recovery – the degree of necrotic injuries and the percentage of seedling survival were also determined.
After 2 days of chilling, the ACC content increased in all genotypes investigated. The increase was significantly higher in the sensitive genotypes than in the tolerant ones. There was a significant correlation between ACC content and necrotic injuries of seedlings. Chilling for 5 days increased the ACC content further and the difference between the two groups of genotypes still existed.
The MACC content increased after 5 days of chilling in all genotypes investigated. The increase was greater in the tolerant genotypes than in the sensitive ones. However, the difference in MACC accumulation between the two groups of genotypes investigated was not significant, and thus no correlation between MACC accumulation and chilling susceptibility was found.
The possible causes for the increase of ACC and MACC contents under chilling conditions and the possibility of using the ACC content as an indicator of chilling tolerance in maize breeding are discussed.     

Dynamics of Growth and Water Relations of Fodderbeet and Seabeet in Response to Salinity

A pot experiment was conducted under greenhouse conditions with two subspecies of beet, fodderbeet ( Beta vulgaris cv. Majoral) and seabeet ( Beta maritima ), under saline conditions. Growth and physiological parameters (dry weight, leaf area, water relations and net photosynthesis) were recorded. The two subspecies responded differently in terms of growth parameters. Plant growth was significantly reduced at 400 m m NaCl, while no significant growth reduction occurred at 200 m m NaCl. Fairly high values of relative growth rate were associated with the leaf area of the cultivars. The water content of the shoot decreased with plant age. The fodderbeet cultivar Majoral showed a significant increase in dry matter at 200 m m NaCl after 5 weeks. This growth improvement may be related to the better adaptation of the plants under saline conditions.     

The Effect of Chilling Temperature on the Permeability of Membranes to K+, Mg2+, Ca2+ ions and on the Electric Potential of Leaves in the Seedlings of Maize (Zea mays L.)

The relations between the extent of injuries in seedlings caused by a few day-long exposures to chill (5°C) and the leakage of K⁺, Mg²⁺ and Ca²⁺ ions from the leaves as well as the electric potential in seven maize hybrids, were investigated. The permeability of cells to ions was defined based on their absolute concentration in a water diffusate (C_t) and concentration expressed in relation to the total ion content in the leaves (IL index).
At lowered temperature the hybrids of higher resistance to chilling temperature were characterized by a lower value of the IL index for K⁺ and Mg²⁺ ions than the chill-sensitive hybrids. On the other hand, absolute concentration of the ions (C_t) Mg²⁺ and Ca²⁺ leaking from the leaves before chill exposure of the seedlings was positively and highly correlated with the extent of injuries in hybrids caused by 4 day-long exposures to chill. This observation is evidence that the chill injuries were predetermined through increased cell permeability to the mentioned ions at room temperature.
Changes in the electric potential of leaves in conditions of lowered temperature preceded the injuries of leaves, which became apparent after a longer period of exposure to chill. Thus, as the leakage of Mg²⁺ and Ca²⁺ ions occurs, changes in the electric potential may supply early information about the predisposition of the particular maize hybrids to chilling injuries. Leakage measurements of Mg²⁺ and Ca²⁺ ions from the leaves at room temperature may find application in the selection of chill-tolerant maize genotypes.     

低温胁迫下籽用西瓜幼苗生理变化与耐冷性的研究

以三叶一心期的籽用西瓜幼苗为材料,采用10℃低温胁迫的方法,研究了黑籽瓜兰州大片(wb10)和红籽瓜巢湖红(wb7)随着处理天数的延长幼苗的耐冷性、光合特性、生理特性的变化规律,以探讨籽用西瓜耐低温的生理机制,从而为籽用西瓜的引种栽培和抗寒品种选育提供理论依据。结果表明:不同品种籽用西瓜幼苗的叶绿素含量、Pn、Tr、Gs、Ci随低温胁迫时间的延长而逐渐降低;Pro、MDA、相对电导率随低温胁迫时间的延长而升高。两品种的冷害指数存在一定差异,耐冷性表现为wb10>wb7。低温胁迫下,耐冷性较强的wb10幼苗叶片中的叶绿素含量、Pn、Tr、Gs、Ci均高于耐冷性较弱的wb7,而耐冷性较强的wb10幼苗叶片中MDA含量、脯氨酸含量、相对电导率均低于wb7。综合试验中各项指标认为,耐冷性与品种的来源、类型及在低温下植株的冷害指数、光合特性和细胞膜稳定性有关。     

Coronatine Enhances Chilling Tolerance in Cucumber (Cucumis sativus L.) Seedlings by Improving the Antioxidative Defence System

Coronatine (COR) is a new plant growth regulator that mimics the biological activities of methyl jasmonate. We determined whether COR enhanced chilling tolerance of cucumber ( Cucumis sativus L. cv. Jinchun 4) seedlings and if such tolerance was correlated with changes in the activity of antioxidant enzymes. COR was applied to seedlings at two-leaf stage at 0 (Control), 0.1, 1, 10, and 100 n m . Seedlings were then subjected to chilling stress at 5 ± 1 °C for 4 days. Seedlings treated with COR showed significant higher tolerance to chilling stress and the optimal concentration was 1–10 n m . Compared with control, the chilling injury index (CII) of the seedlings treated with COR at 1 and 10 n m was decreased by 44.9 % and 24.5 %, respectively, while the membrane chilling stability (MCS) expressed as the change of relative conductance was increased by 37.2 % and 17.0 %, respectively. The malondialdehyde (MDA) content in leaves treated with COR at 1 n m was decreased by 39.7 %, and the O₂⁻ production rate and H₂O₂ content reduced by 28.6 % and 8.5 %, respectively. Treatment with COR at 1 n m increased the activities of superoxide dismutase (SOD) in leaves by 34.4 %, catalase (CAT) by 58.7 % and ascorbate peroxidase (APX) by 23.0 % under low temperature. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities were also significantly improved by 28.9 % and 21.3 % following treatment with COR at 1 and 10 n m , respectively. The overall results suggest that COR enhanced chilling tolerance in cucumber seedlings by improving the antioxidative defence system.     

Differential Drought Responses of Faba Bean (Vicia faba L.) Inbred Lines

Drought responses of 19 inbred faba bean lines of different origin were studied in the field under rain shelters with and without irrigation. Inbred lines differed significantly in response to drought (P < 0.01): those with a lower drought sensitivity index (SI) (more resistant) originated from the drought-prone regions characterized by smaller plant size (r = 0.93), and more pods and seeds per plant (r ≥ 0.90) regardless of seed size, while lines with higher SI (more sensitive) were those which mainly exhibited higher yield under favourable conditions accompanied by a greater biomass. In a greenhouse experiment under mild drought (−0.15 MPa soil water potential), comparisons between relatively drought-sensitive (Adriewaalse) and drought-resistant (L7) inbred lines showed that Adriewaalse used 38 % more water than L7 and also produced 40 % more biomass. There was a stress-induced decrease in osmotic potential (ψ_s) in both lines (by 0.72 and 0.50 MPa for Adriewaalse and L7, respectively) accompanied by decreased turgor in Adriewaalse and increased turgor in L7. The difference in drought-induced solute accumulation between lines was diminished when solute accumulation due to water loss and growth inhibition was considered, which indicates that solute accumulation was the result of a concentration effect. Similarly, lower SI in the field was not the result of osmotic adjustment, as the relationship between SI and drought-induced decrease in ψ_s was negative. The water use efficiency of both inbred lines increased markedly with increasing water deficit, though there was no difference between the lines. It was concluded that differences in drought resistance between these inbred faba bean lines were manifested through plant size-induced water demand (avoidance) but were not associated with osmotic adjustment (tolerance).     

Organic Recycling for Soil Quality Conservation in a Sub-tropical Plateau Region

The long-term effect of organic recycling on some aspects of quality in a lowland rice soil of an Indian plateau region was studied. The experiment was set up at the agricultural experimental farm of the Indian Statistical Institute, Giridih, Bihar, India. Two rice cultivars, and treatments with four organic supplements (cowdung manure, Leuceana leaves, decomposed farm residue and Sesbania ), chemical fertilizers (urea, superphosphate and muriate of potash) and no input were arranged in a factorial randomized block design. Organic supplements improved soil quality parameters such as water holding capacity, total organic C, microbial biomass C, urease and acid phosphatase activities of soils in comparison to chemical fertilizers and no input. Among the organic supplements, cowdung manure gave significantly higher organic C (1.39%), microbial biomass C (276.46 μg g⁻¹ dry soil), urease activity (32.79 and 21.22 μg urea hydrolized g⁻¹ dry soil h⁻¹ at 37 °C by the buffer and non-buffer method, respectively) and acid phosphatase activity (1.99 μmol p-nitrophenol released g⁻¹ dry soil h⁻¹ at 37 °C) than the others. The conversion of organic C into biomass C (2.46%) was highest in Leuceana -treated soil.     

Water Requirements for Castor Oil Crop (Ricinus communis L.) in a Mediterranean Climate

A field study was conducted to assess the effect of irrigation on castor ( Ricinus communis L.) and to define the water requirements of the crop. Three irrigation regimes, corresponding to 0.0, 0.5 and 1.0 fractions (kd) of the evapotranspiration (ETm) in the area were compared, factorially combined with the varieties Pronto and Negus in 1995. In 1996 and 1997 one more irrigation treatment corresponding to 0.75 of the ETm was included, and Negus was replaced by HD912. Irrigation was found necessary for castor production since seed and oil yields obtained with irrigation were much higher compared to yields of rainfed plants, and also castor could not be competitive to winter cereals in rainfed areas. In 1995 seed yield increased to kd = 1.0, but the response of both varieties was curvilinear. In 1996 kd = 0.50 was enough for the maximum yield by both varieties, while in 1997 higher amounts of water were needed (kd = 1.00 and 0.75 for Pronto and HD912, respectively). The beneficial effect of irrigation was mainly due to the increased number of secondary racemes. Oil yield was mainly determined by seed yield. Thus, the aim of the growers should be to increase the seed yield. The suggested amount of water for the irrigation of castor in the Northern Greece is equal to 75 % of the evapotranspiration of the plant in the area. With this amount the yield is satisfactory and the management of water resources is doing in a rational way.     

Effect of Secondary Salinization on Photosynthesis in Fodder Oat (Avena sativa L.) Genotypes

The effect of secondary salinization on photosynthesis was studied in fodder oat genotypes Kent, JHO-829, JHO-881, UPO-94 and OS-6 at the flower initiation stage. With an increase in the electrical conductivity (EC) of irrigation water, the net photosynthesis rate (P_N) and the transpiration rate (E) of all the genotypes decreased. The intercellular CO₂ concentration (Ci) increased in all genotypes at 10 dS m^−1. Stomatal resistance (R_s) had a strong negative correlation with PN and E. The increase in Ci together with the increase in the R_s shows that at higher EC non-stomatal factors also start contributing to the limitation of photosynthesis. This study suggests that secondary salinization effects are strongly under stomatal control at lower saline water irrigation levels, but at higher levels non-stomatal factors may come into play.     

Effect of Low Soil Temperature on Weight Increase, Gas Exchange and Distribution of 14C-Assimilates in Seedlings of a Maize Hybrid

Seedlings of a maize hybrid sensitive to chilling initially grew in the growth chamber of the phytotron at 20/ 17°C (day/night) and after the formation of the fourth leaf, the soil temperature was lowered to 5°C. Under such growth conditions the dynamics of dry weight change, gas exchange and the distribution of ¹⁴C-assimilates in seedlings were examined. The low soil temperature inhibited daily growth of dry weight of whole seedlings more than their photosynthesis. Simultaneously, it was also responsible for a greater increase in dissimilative losses.
During 37 hours (day-night-day), following exposure to ¹⁴CO₂, dissimilation in seedlings in cool soil (5°C) and in non-chilling conditions amounted to 35.1 % and 23.4 % of assimilated ¹⁴C (AC), respectively. At lower soil temperature relatively high dissimilative losses were observed on the first day after exposure (23.5 %), lower at night (9.9 %) and the lowest on the following day - merely 1.7 % AC. Higher losses of ¹⁴C under chilling conditions occurring on the first day were a result of limited photosynthetic refixation of ¹⁴CO₂ At night, however, they were associated with a prolonged period of intensive translocation of assimilates to the stem. It was assumed that an excessive accumulation of assimilates in leaf blades might be an additional factor responsible for increased dissimilative losses at low temperature during the first twenty-four hours. In the third period of measurements, as a result of a limited transport of ¹⁴C, dissimilative losses were lower than in previous ones and were not dependent upon soil temperature.     

干旱胁迫下外源油菜素内酯对玉米幼苗光合作用和D1蛋白的调控效应

为了揭示干旱胁迫下外源油菜素内酯对玉米幼苗光合作用的保护机制,采用溶液培养的方法,以驻玉309为试验材料,研究外源油菜素内酯(BR)预处理及20% PEG-6000模拟干旱胁迫后玉米幼苗的生长参数、叶绿素含量、光合参数、叶绿素荧光参数及D1蛋白含量的变化。结果表明,与干旱胁迫处理(PEG)相比,BR+PEG处理的玉米苗株高增加45.87%,根长增加20.56%,总干物质积累增加8.01%,叶片相对含水量提高4.50%,叶绿素a含量增加26.32%,光合参数(Pn、Gs、Ci、Tr)分别提高9.57%,38.23%,30.19%,28.12%,光合系统Ⅱ(ΦPSⅡ)活性提高了20.48%,最大光化学效率提高了0.66%,光合系统Ⅱ绝对电子传递速率(ETR(Ⅱ)和相对电子传递速率r ETR(Ⅱ))分别提高20.40%和31.02%;D1蛋白含量增加37.34%(P0.05)。说明在干旱胁迫条件下叶片喷施BR可以改善玉米幼苗的生长发育,减缓光合系统的损伤,促进D1蛋白质的稳定,从而提高玉米幼苗对干旱胁迫的适应性。     

The Change of Heat Emission and Phenolic Compound Level in Hordeum vulgare (L.) and Festuca pratensis (Huds.) Calli Treated with Bipolaris sorokiniana (Sacc.) Shoem. Phytotoxins

The presented work was conducted on calli of spring barley and meadow fescue that differed in degree of sensitivity to leaf spot pathogen Bipolaris sorokiniana . Callus reaction to fungus phytotoxins was examined on the basis of the amount of total phenolics and heat emission. The study was conducted dynamically – the measurements were performed after 1, 3, 6, 10, 24, 48, 72, 168 and 240 h after the moment when the calli were elicited with fungus metabolites. The greatest metabolic activity of fescue calli was observed between the 6th and the 24th h after treatment with phytotoxins and amounted to 170 % of control values. On the 10th day of culture this activity dramatically decreased in comparison with control (17 %). In the case of barley calli, increased heat emission was registered during the first 10 h of pathogenesis (130–150 % of control values). Calli of both studied plant species also differed in the dynamics of phenolic content changes. In meadow fescue tissue a significant decrease in phenolic level in comparison with control (40 %) was observed after the 7th day of experiment. In barley calli the amount of total phenolics decreased within the first 3 h (60–70% of control). The results obtained show that spring barley and meadow fescue differ in the rate of reaction to B. sorokiniana phytotoxins with regard to changes in metabolic activity and phenolic content. It also suggests a different degree of the plants sensitivity to the studied pathogen on tissue level.