The relationship between nutrient composition, crop biomass, and glutamate dehydrogenase (GDH) isoenzyme pattern was investigated in soybean (Glycine max) and maize (Zea mays) by monitoring the nutrient induced isomerization of the enzyme from the seedling stage to the mature crop. GDH was extracted from the leaves of the plants, and the isoenzymes were fractionated by isoelectric focusing followed by native polyacrylamide gel electrophoresis. The isomerization V_max values for soybean GDH, similar to maize GDH increased curvilinearly from 200 - 400 μmol mg^-1 min^-1 as the inorganic phosphate nutrient applied to the soil decreased from 50 - 0 mM. In soybean, combinations of N and K, P, or S nutrients induced the acidic and neutral isoenzymes, and gave biomass increases 25 - 50 % higher than the control plant. GDH isoenzymes were suppressed in soybean that received nutrients without N, K, or P and accordingly the biomass was about 30 % lower than the control. Treatment of maize with NPK nutrients increased the GDH V_max values from 138.9 at the vegetative to 256.4 μmol mg^-1 min^-1 at the reproductive phase, and suppressed the basic isoenzymes, but induced both the acidic and neutral isoenzymes thereby inducing seed production (27.0 ± 1.4 g per plant); whereas both the acidic and basic isoenzymes were suppressed in the control maize, and seeds did not develop. Simultaneous induction of the acidic, neutral, and basic isoenzymes of GDH indicated the occurrence of senescence. Therefore in maize and soybean, the induction of the acidic and basic isoenzymes of GDH led to the enhancement of biomass.

Gas exchange in paclobutrazol-treated triticale plants during water stress and rehydration was studied. Seed treatments with the retardant (1 and 25 mg dm^-3) alleviate negative effect of PEG-induced water stress. Net photosynthetic rate, transpiration rate, stomatal conductance, relative water content, and leaf water potential were higher while peroxidase activity and free proline concentration were lower in the paclobutrazol-treated plants than in control plants. This confirmed our assumption that paclobutrazol possessed a protective effect against water stress.

Exposure of groundnut seeds and seedlings to 25, 100, and 250 μM concentrations of jasmonic acid resulted in a reduction of germination percentage, growth, fresh mass, dry mass, chlorophyll content, chlorophyll stability index, proteins and an increase in free proline content and cell membrane injury. The results suggest the inhibitory effect of jasmonic acid on growth of the groundnut seedlings.

Role of superoxide dismutase isozymes and other antioxidant enzymes was studied in relation to leaf age in sunflower (Helianthus annuus L. cv. ACC 1508) at pre-flowering and grain filling stages. Relative water content (RWC) did not change much in leaves of different age and at the two stages. Protein content declined continuously from the youngest to the oldest leaf, while chlorophyll (Chl) and carotenoids (Car) contents increased down to 7^th/9^th leaf and declined in subsequent older leaves. Protein, Chl and Car contents were higher at pre-flowering than at seed filling stage. Superoxide dismutase (SOD), its isozymes, and ascorbate peroxidase (APO) and catalase (CAT) activities were highest in the 9^th leaf and declined in subsequent older leaves. SOD and APO activities were higher at seed filling, except in oldest senescent (13^th, 15^th) leaves. Among SOD isozymes, Cu/Zn-SOD and Mn-SOD activities accounted for most of the total SOD, and only marginal activity was observed for Fe-SOD. Peroxidase activity increased from youngest to the oldest leaf at pre-flowering stage and down to 13^th leaf at seed filling stage.

Effects of plant hormones indole-3-yl-acetic acid (IAA), gibberellic acid (GA), benzylaminopurine (BAP), abscisic acid (ABA) and ethrel (ETH) in 5 μM concentration on gas exchange, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO, EC 4.1.1.39) activity, pigment content and yield in cotton (Gossypium hirsutum L. cv. H-777) under drought were studied. At reproductive stage (55 - 60 d after sowing) these hormones were sprayed on shoots one day prior to stress imposition by withholding irrigation. The soil moisture of control plants was kept at field capacity. Net photosynthetic rate (P_N), stomatal conductance (g_s), transpiration rate (E), carboxylation efficiency (CE), water use efficiency (WUE), RuBPCO activity, boll number per plant, seed number per plant and lint mass per plant significantly decreased at drought while chlorophyll (Chl) b content and flower number per plant increased. ABA and ETH significantly reduced gas exchange parameters, Chl a and Chl b content. Detrimental drought effect on P_N, g_s, E, CE, RuBPCO and lint mass per plant was significantly alleviated by BAP and also its effect on seed number and lint mass per plant was significantly alleviated with the ABA treatment.

This study was conducted to determine effects of nitrogen supply (75 and 150 kg(N) ha^-1) and CO₂ enrichment on partitioning of macro and micro nutrients in wheat (Triticum aestivum L. cv. HD-2285). Plants were grown from seedling emergence to maturity inside open top chambers under ambient CO₂ (CA, 350 ± 50 μmol mol^-1) and elevated CO₂ (CE, 600 ± 50 μmol mol^-1). Leaves, stems and roots of the same physiological age were analyzed for carbon, nitrogen, calcium, copper, iron, zinc and manganese content at 40, 60 and 90 d after germination. C, Cu, Mn and Zn content was higher in the stem, leaves and roots on dry mass basis under CE than CA. However, N and Fe contents decreased in CE grown plants. Ca content was unaffected due to CE and variable N supplies.

Trigonelline (TRG) is a conjugate of nicotinic acid, and is postulated to function as a compatible solute in response to salinity- and water deficit-stresses. TRG concentrations and several agronomic characteristics were measured under irrigated field and non-irrigated field conditions within 18 soybean (Glycine max) genotypes using leaves taken from different growth stages (vegetative, flowering and pod development). Under irrigation, relative water content (RWC) ranged from 90.0 to 99.6 %. Under non-irrigation, RWC ranged from 86.3 to 97.5 %. TRG concentration ranged from 364 to 555 μg g^-1(d.m.) under irrigation, and from 404 to 570 μg g^-1(d.m.) under non-irrigation. TRG concentrations increased in the majority of genotypes (15 of 18) under non-irrigation even though RWC did not significantly differ in many genotypes between treatments. TRG decreased as plants progressed to pod development and seed filling. Mean seed yield under non-irrigated conditions declined 55 % relative to the irrigated controls. TRG concentrations among all genotypes were significantly correlated with seed yield.

The effects of different paraquat, alachlor and metolachlor concentrations on superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX) activities and pigment contents in lettuce, bean and pea seeds and leaves were studied. Under paraquat (1.0 and 2.0 μM) treatment declined SOD and CAT activities were observed in seeds and undetectable ativity of GPX. Germination of all investigated seeds was completely inhibited. All used concentrations of alachlor and metolachlor inhibited antioxidant enzyme activities in seeds but did not prevent germination and growth. In leaves, lower concentrations of these herbicides increased activities of antioxidant enzymes but at the highest herbicide concentrations (200 μM) activities of investigated enzymes declined. The pigment contents the leaves decreased due to alachlor and metolachlor treatment in a concentration dependent manner.

Vicia faba seeds were treated with methyl methanesulphonate (MMS) and stored at 50 % water content for 0, 14 and 28 d. This water content prolongs the period between the mutagenic treatment and the onset of DNA synthesis. Storage of seeds after mutagen treatment at the selected water content led to a significant decrease in DNA damage, manifested as a reduction in the frequency of chromosomal aberrations.

The isolation and characterisation of cotyledonary ribonucleases (RNase; EC 3.1.27.1), are basic steps to understand the physiology and biochemistry of RNA turnover and mobilisation during seed germination and seedling establishment, as well as how environmental stresses affect them. RNase was isolated and purified 928-fold, to apparent electrophoretic homogeneity from 5-d-old seedlings of Vigna unguiculata. It is a protein with an apparent molecular mass of 16 kDa having three major isoforms. Its optimum pH is 5.8, which decreases to 5.2 in presence of KCl. It has an apparent K_m of 0.80 mg RNA cm^-3 and retains 40 % of its activity when heated to 80 °C. It is completely inhibited by Cu²⁺, Hg²⁺ and Zn²⁺ and is almost insensitive to Mg²⁺, Ca^2+- and EDTA. Urea, Fe²⁺, Co²⁺ and 2-mercaptoethanol partially inhibit its activity. Its amino acid composition shows a resem lance to that of other plant RNases.

Regeneration of Plumbago rosea L., a rare medicinal plant, via somatic embryogenesis in callus cultures derived from leaf explants was described. Optimum callus formation was achieved on semi-solid Murashige and Skoog (MS) medium supplemented with 0.25 mg dm^-3 kinetin and 2.0 mg dm^-3 1-naphthaleneacetic acid (NAA). Somatic embryogenesis was achieved upon transferring the 4-week-old callus to a medium containing 1.0 mg dm^-3 kinetic (Kn), 0.5 mg dm^-3 gibberellic acid (GA₃) and 0.1 mg dm^-3 NAA. Embryo maturation and germination was achieved on the half-strength MS basal salts supplemented with 0.01 - 0.25 mg dm^-3 Kn and 2 % (m/v) saccharose. An average of 50 - 60 plantlets were obtained from 150 mg of embryogenic callus within 4 week of subculture. Out of the 50 plantlets about 28 survived in the greenhouse.

All seeds of Aeluropus lagopoides and Urochondra setulosa germinated under non-saline conditions except for Sporobolus ioclados which showed only 40 % germination. Increase in salinity substantially inhibited germination and few seeds germinated at 400 mM NaCl. Germination at 200 mM NaCl was alleviated in U. setulosa by the application of gibberellic acid and fusicoccin, in A. lagopoides by thiourea, betaine, kinetin, fusicoccin and ethephon, and in S. ioclados by gibberellin and ethephon. High salinity (400 mM NaCl) induced germination inhibition was alleviated by proline, kinetin, fusicoccin and ethephon only in A. lagopoides.

With the aim to determine the effects of CO₂ on nitrogen metabolism mungbean (Vigna radiata) plants were grown from seedling emergence to maturity inside open top chambers under ambient CO₂ (CA, 350 ± 25 µmol mol^-1) and elevated CO₂ (CE, 600 ± 50 µmol mol^-1) concentrations at the Indian Agricultural Research Institute, New Delhi. Leaflet blades of the same physiological age were sampled at 20, 35 and 50 d after germination. Total nitrogen concentration in dry mass was consistently lower under CE than in CA. Non-protein nitrogen and protein nitrogen were also decreased under CE Total soluble protein content also decreased up to 35 d after germination under CE. However, a 27 % increase in protein content at 50 d after germination due to CE was observed. A significant decrease in total free amino acid under CE at 20 d after germination was observed. CE also brought about a remarkable decrease in the activity of nitrate reductase in leaves at 20 d after germination but increase at 35 d and 50 d after germination. Nitrogenase activity increased at all growth stages due to CE. Although total harvested leaves of CE plants accumulated more nitrogen, the relative amount of nitrogen on a percentage basis was low, probably due to a comparatively greater accumulation of sugars in the leaves of CE plants.

With the imposition of salt stress (0.5 to 3 % NaCl or CaCl₂) a decrease in germination rate and accumulation of proline was observed in the root tissue. Both NaCl and CaCl₂ solutions induced an increase in the total peroxide content and lipid peroxidation and decrease in catalase, guaiacol peroxidase and superoxide dismutase activities in root tissues suggesting an oxidative stress in the salt sensitive rice cultivar.

The effects of increasing relative humidity on the growth and salt tolerance of two melon (Cucumis melo L.) cultivars, Revigal C-8 (salt sensitive) and Galia (salt tolerant) was investigated. One month after germination, the plants were exposed for 15 d to 0 (control) and 80 mM NaCl, under relative humidity (RH), 30 and 70 %. The growth of the whole plant, leaf, stem and root of cv. Revigal C-8 was increased with increasing RH. On the other hand, cv. Galia showed an increase in root growth with increasing RH only under the NaCl treatment. Under salinity, most of the Na⁺ was withheld in the stems. An increase in RH in the NaCl treatment significantly decreased Na⁺ and Cl^- concentrations in leaves of cv. Revigal C-8, while it had no effect on their concentrations in cv. Galia. In both cultivars, increasing RH under NaCl condition significantly decreased water contents in leaves and stems, and increased osmotic potential in roots. The amount of the root exudate of cv. Galia was significantly decreased with increasing RH, while it was not affected in cv. Revigal C-8. Under the NaCl treatment, cv. Galia had significantly higher leaf osmotic potential than cv. Revigal C-8 at both relative humidities and higher amount of root exudate at 30 % RH.

Lupinus albus L. seeds were treated with different concentrations (from 10 µM to 50 mM) of H2O2, m-chloroperoxybenzoic acid (mCPBA), ascorbate (ASC) and glutathione (GSH). The efficiency as inhibitors on germination and on the subsequent growth of the hypocotyl was mCPBA > GSH > ASC = H2O2, which suggest that inhibitory efficiency was dependent on the compound per se rather than on its redox nature.

Rhizobacteria belonging to Bacillus sp. were isolated from the rhizosphere of green gram (Vigna radiata). Seed inoculation with the rhizobacteria showed stunting effect on root growth whereas four Bacillus strains caused stimulation of shoot growth at both 4 and 7 d of observations. Coinoculation of some Bacillus strains with effective Bradyrhizobium strain S24 resulted in enhanced nodulation and plant growth of green gram. The shoot dry mass (ratio to uninoculated control) varied from 1.32 to 6.33 at day 30 and from 1.28 to 3.55 at day 40 of plant growth. Nodule promoting effect after 40 d of plant growth was observed with majority of Bacillus strains except for MRS9 and MRS26. Maximum gains in nodulation, nitrogenase activity and plant growth were observed with Bacillus strains MRS12, MRS18, MRS22 and MRS27 after 40 d of plant growth, suggesting the usefulness of introduced rhizobacteria in improving crop productivity.

Plant regeneration was achieved from the seed derived decotyledonated split embryo axes of six Indian cultivars of cotton (Gossypium hirsutum L.). Explants were cultured on Murashige and Skoog's basal medium supplemented with 2 % sucrose and 0.65 % agar. Incorporation of 0.25 % charcoal in the medium and incubation of the cultures at 30 ± 2 °C had synergistic effect on the frequency of shoot and root formation. The method employed is genotype independent, simple and rapid.

Endogenous gibberellin-like activity was determined in dry pea seeds (Pisum sativum cv. Bördi), in cotyledons and axes of germinating pea seeds and also in excised cotyledons and axes. During the first two days of pea seed germination, neither the embryonic axes nor the cotyledons show a mutual influence on gibberellin activity, but this appears after 72-96 h of germination. The gibberellin-like activity m cotyledons and axes of germinating seeds increased during the same period, but it decreased in isolated axes and excised cotyledons.

Ethanol can influence germination of seeds ofPinus halepensis. When supplied by the appropriate procedure, the anaesthetic is able to mimic light in stimulating seed germination. This action is interpreted in terms of changes in membrane properties.

Zilla spinosa plant part extracts exhibited significantly different inhibitory effect on the seed germination and seedling growth of its associate species. Shoot extract reduced the percentage germination and seedling length of different test species more than root extract. Except of Z. coccineum, seedling growth was more sensitive than seed germination. Shoot/root ratio of all test species increased significantly with increase in extract concentration. Mycelia growth of the two rhizosphere fungal species was more significantly reduced by Z. spinosa shoot extract than root extract. The effects of the different extracts on total protein and total carbohydrate contents of the two test species were comparable. Non-significant increase was recorded at low concentration of both shoot and root extract. However, with the rise of extract concentration, highly significant reduction in the content of these metabolites was recorded.

Frequency of safflower (Carthamus tinctorius L.) somatic embryogenesis, number of somatic embryos per responding explant and somatic embryo maturation and germination were affected by genotype, explant age, carbon source, and ethylene. Among 8 cultivars tested, 7 were embryogenic with varying frequencies. The best response was obtained with cv. Girna. Whole cotyledonary explant from 10-d-old plants was best responding compared to 5- or 15-d-old ones. Among different carbon sources, sucrose at 87.6 mM concentration was most suitable for embryo induction, maturation and germination. Of the different ethylene inhibitors, silver nitrate at 50 [micro ]M concentration significantly increased the embryogenic frequency and also the number of embryos per responding explant. Silver nitrate has pronounced effect on embryo maturation but had no effect on germination.

Standardized laboratory techniques for the vegetative growth of the duckweedSpirodela polyrhiza (Lemnaceaé), and for formation as well as germination of their turions were described. Increasing photon fluence rates of blue or red light increased the yield of turions. A specific stimulating effect of blue light was demonstrated under autotrophic but not under mixotrophic conditions. Therefore the spectral composition of light is not important in mixotrophic formation of turions whereas in autotrophic formation light sources with a higher portion of blue light are recommended. Dark-grown (etiolated) turions showed accelerated germination and higher germination percentage in comparison with light-grown turions after induction by a single red light pulse. This difference was overcome in continuous red light by speeding up the germination response of light-grown turions. Use of Petri dishes (8 cm³ nutrient solution) instead of Erlenmeyer flasks (50 cm³ nutrient solution) retarded germination response. Especially for long term experiments the use of Erlenmeyer flasks is recommended. Storage of turions for 72 h at 25 ‡C following at 5 ‡C in darkness after-ripening resulted in a decreased lag phase of the light-induced germination both after induction by a single light pulse and in continuous light.

Steam-girdling experiments with detached wheat shoots showed that cesium was eliminated from the xylem sap and loaded into the phloem during acropetal transport. This transfer is important for the accumulation of cesium (especially also of the radiopollutants ¹³⁴Cs and ¹³⁷Cs) in maturing wheat grains.

Inheritance of chloroplast DNA (cpDNA) was examined in 41 F₁ progeny obtained from the following interspecific Bromus crosses: Bromus arvensis (2n = 14) × B. inermis (2n = 4x = 28); B. arvensis × B. inermis (2n = 8x = 56); B. arvensis × B. erectus (2n = 6x = 42); B. arvensis × B. erectus (2n = 8x = 56); B. arvensis × B. erectus (2n = 10x = 70). Chloroplast DNA of the parental species was digested with BamHI, EcoRI and HindIII and species-specific restriction fragment length polymorphisms were identified by observation of ethidium bromide stained agarose gels as well as by filter hybridization experiments involving heterologous cloned barley cpDNA probes. The stability of these point mutations was verified by examining the cpDNA restriction patterns of at least 28 individual plants raised from seed of each of the parental species. No intraspecific cpDNA variability was detected. All the F₁ progeny examined exhibited the cpDNA restriction fragment patterns of the female parent. There was no evidence of any paternal or biparental cpDNA inheritance. The results provided evidence for the uniparental-maternal inheritance of cpDNA in the Bromus crosses examined.

Qualitative and quantitative differences in cytokinin levels of gram seeds were observed during germination of control and 6-benzylaminopurine (BAP; 4.44 x 10^t-5 M) treated seeds. Zeatin riboside (ZR), zeatin (Z), dihydrozeatin (DHZ), isopentenyladenosine (iPA) and isopentenyladenine (iP) were determined using high pressure liquid chromatography. In the control seeds the ZR content increased markedly only after 24 h of germination. In BAP treated seeds, the increase in ZR content was stronger than in control seeds and it persisted during further germination. Z content increased during germination in both control and treated seeds. After 48 h of germination iP appeared in control and especially in treated seeds.

The allelopathic potential of Ageratum conyzoides, which is one of the most dominant weeds in upland-crop areas of Southeast Asia, was investigated under laboratory conditions. The residue obtained from an aqueous acetone extract of the plant shoots inhibited the germination and the growth of roots and shoots of Amaranthus caudatus, Digitaria sanguinalis and Lactuca sativa. The concentration-dependent responses of the test plants suggest that the residue of Ageratum conyzoides might contain allelochemical(s).

The allelopathic potential of four tree species on soil microbial populations and some herbaceous plants (two understory species and one general biotest species) was investigated. Effects of three nonindigenous tree species, Eucalyptus globulus Labill, Pinus radiata D.Don and Acacia melanoxylon R.Br., on microorganisms participating in the cycle of nitrogen were evaluated, comparing them with those produced by the autochthonous Quercus robur L. Influence of the trees on Lactuca sativa L., Dactylis glomerata L. and Trifolium repens L. was also checked in bioassays. Cell numbers of Nitrosomonas sp. were negatively affected by Acacia and Eucalyptus stands, mainly during spring, when flowers are especially abundant on the ground. Proteolytic microorganisms were also negatively affected by Eucalyptus and Pinus stands, whilst Quercus stand did not show any toxicity. Soil bioassays showed clear inhibitory effects on germination and growth of understory plants, particularly soils from Eucalyptus and Acacia stands. The greatest effects had the soil from Acacia stand, which was phytotoxic during the whole period of germination and growth of understory plants. Allelopathic phenomena could be, at least partially, responsible of the low species diversity in the understory of the nonindigenous tree stands.

Effect of two important mycotoxins, aflatoxin B1 and citrinin (concentration 2 g m-3) at various combinations (i.e., 1:1, 1:2, 2:1, 1:3 and 3:1, v/v) on seed germination, seedling growth, chlorophyll, carotenoid, starch, sugar, protein and nucleic acid contents, α-amylase activity, and respiration quotient was studied in maize cv. Suwan composite. The maximum and minimum inhibitions were recorded in most of the above parameters (except starch) at 3:1 and 1:3 combination ratios of these toxins, respectively. However, the inhibition rates varied with the treatments.