A galactose-binding lectin was isolated in electrophoretically pure form from the seeds of the snake gourd,Trichosanthes anguina, by affinity chromatography on an immobilised lactose column, as well as on a cross-linkedGuar Gum column. The lectin agglutinates native erythrocytes of human A, B and 0 phenotypes and of rabbit, rat and mouse. The molecular mass of the lectin, as estimated bySephadex G-200 gel chromatography, is 49 kDa. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis, after reduction with β-mercaptoethanol, revealed two polypeptide chains linked by disulphide bonds in the lectin molecule. It contains no covalently linked sugars. Amino acid analysis of the lectin revealed a high content of acidic amino acids, relatively lower proportion of basic amino acids and traces of cysteine and methionine. The lectin has good thermal stability, and is inactivated when oxidised by metaperiodate.

Binding protein for N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, was studied by analysis of the effects of reactions which modify particular amino acid side chains upon their binding activity. Na₂SO₃, N-ethylmaleimide (NEM) and dithiobisnitrobenzoic acid all inhibited the specific binding of NPA to its binding protein fromAcer pseudoplatanus L. cells. The presence of 10^-6 M Na₂SO₃ in the binding assay reduced the affinity of the binding protein to NPA from K_d of 1.5 £ 10^-8 M to K_d of 2.1 £ 10_-8 M, while concentration of the binding protein was not significantly changed. When the same analysis was applied to NPA binding to the NEM-treated membrane particles, it was found that NEM inactivated binding without changing the affinity for NPA. This study revealed the importance of sulphydryl group(s) in the maintenance of NPA binding protein activity.

The plants of mustard (Brassica juncea L.) were treated with 0, 25 and 50 ΜM gibberellic acid (GA₃) at three fully developed leaf stage (30 d after sowing). Effect of GA₃ on carbonic anhydrase activity, photosynthetic rate, leaf area index and dry mass was studied at 50, 70 and 90 d after sowing. At harvest 1000 seed mass, pod number and seed yield were recorded. GA₃ treatment (50 ΜM) enhanced all the characteristics studied.

Echinochloa colona regeneration via organogenesis in callus cultures derived from leaf base and mesocotyl expiants andin vitro flowering were achived. Shoot bud regeneration was achieved on Murashige and Skoog's (MS) basal medium supplemented with 6.66 μM 6-benzylaminopurine (BAP), 2.68 μM 1-naphthalene acetic acid (NAA) and 3 % (m/v) saccharose. Regenerated shoots were rooted on half strength basal MS medium with 2 % (m/v) saccharose devoid of growth regulators. About 90 -95 % of rooted plantlets survived in the greenhouse.In vitro flowering was induced in the regenerated shoots derived from callus on half strength MS medium supplemented with 4.4 μM BAP, 74.07 μM adeninesulphate, 0.72 μM gibberellic acid, and 3 % (m/v) saccharose. The frequency ofin vitro flowering was 80 - 90 % in three repeated experiments. Fertile seeds were recovered fromin vitro grown plantlets which were subsequently germinated into plants.

Pathogenesis-related (PR) proteins from pepper (Capsicum annuum L.) cv. Americano (tolerant) and cv. Smith-5 (sensitive), both elicited by infection with cucumber mosaic virus (CMV), were assayed for chitinase and glucanase activities. Two basic PR-proteins, M_r 49.0 and 28.0 kD, were elicicited from the intracellular fraction (INTRA-F) of both cvs. by CMV infection, while four acidic M_r 15, 19, 36 and 40 kD and two basic M_r 21.2 and 24 kD PR-proteins were elicited from the intercellular fluid (IF) of cv. Americano leaves. Five acidic M_r 21.5, 23.2, 24.4, 25.2 and 36 kD and five basic M_r 23.3, 26, 28.8, 30 and 32.3 kD PR proteins were elicited from the IF of cv. Smith-5. Isoelectric focusing (IEF) of the IF and the INTRA-F proteins revealed the occurrence, in both pepper cultivars, of one acidic M_r 36 kD and one basic M_r 25 kD PR-protein with glucanase activity. After native-PAGE for acidic proteins, the acidic PR-protein of Rf 0.7 and M_r 36 kD present in the IF of both pepper cvs. showed glucanase activity. Native-PAGE for basic proteins of the INTRA-F showed the presence of one band (Rf 0.61, M_r 25 kD) common to both cvs. and two additional bands (Rf 0.49, M_r 26 kD and Rf 0.79, M_r 33 kD) in the cv. Americano with glucanase activity. The specificity shown by the basic PR-proteins suggests glucanase activity is involved in the mechanisms of resistance to CMV in the cv. Americano. There was no difference in chitinase isoform patterns between the two pepper cultivars analyzed. After IEF of the IF proteins, one acidic chitinase isoform was detected. Native-PAGE separation of the IF showed one band (M_r 30 kD) with chitinase activity. Chitinase activity was not detected in the INTRA-F of either cultivar.

Leaf gas exchange, plant growth and leaf ion content were measured in wheat (Triticum durum L. cv. HD 4502) exposed to steady- state salinities (1.6, 12.0 and 16.0 dS nr^-1) for 8 weeks. Salinity reduced leaf area and number of tillers, and increased Na⁺ and Cl^- concentrations in leaves. Leaf- to- leaf gradients of these ions were observed. The oldest leaf contained 6 to 8 times more Na⁺ and Cl^- than the flag leaf. Net photosynthetic rate (P_N), transpiration rate (E) and stomatal conductance (g_S) were the highest in flag leaf, declined in the middle and fully expanded leaves, and were minimum in the oldest leaves. These processes were reduced by salinity with similar leaf- to- leaf gradients. Intercellular CO₂ concentrations in the older leaves were higher than in the flag leaf in non-saline plants, and increased similarly with salinity. Leaf age was the major factor in reducing P_N, and senescence processes were promoted by salinity.

Changes in various components of photosynthetic apparatus during the 4 d dark incubation at 25°C of detached control and ultraviolet-B (UV-B) treatedVigna unguiculata L. leaves were examined. The photosynthetic apparatus was more degraded in younger control seedlings and for a longer time UV-B treated seedlings than in the older or for a shorter time UV-B treated seedlings. This was shown by determining the losses in chlorophyll (Chl) and protein contents, variable fluorescence yield, photosystem (PS) 2, PS1 and ribulose-1,5-bisphosphate carboxylase (RuBPC) activities, and photosynthetic¹⁴CO₂ fixation. In contrast, the Car/Chl ratio increased during the dark incubation due to less expressed degradation of Car.

The changes in ubiquitin mRNA level in intact plants of both susceptible (cv. Spunta) and partially resistant (cv. Pampeana-INTA) potato cultivars after inoculation with low doses (l0³ sporangia cm^-3) ofPhytophthora infestons were studied after 72 h of treatment. Inoculation leads to 5-fold accumulation of potato ubiquitin transcripts in both cultivars. This result supports the connection between ubiquitin expression and defense reaction in plants.

Dynamics of CO₂ evolution at low pressure was studied in barley, maize, pea, wheat and pine seedlings using the gas exchange system with laser photoacoustic spectrometer. The CO₂ evolution from plant surfaces to environment increased with decreasing air pressure. Simultaneously the changes in activities of phosphoenolpyruvate carboxylase, glucose-6-phosphate dehydrogenase, glyceraldehyde phosphate dehydrogenase, alcohol-dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase in pea and maize leaves were observed. The response depended on plant species used as well as on air pressure and period of its action

Regenerants were produced from axillary buds, but not from petiole segments, greenwood cuttings and leaf discs. Petiole segments and greenwood cuttings responded by massive callus cell proliferation without adventitious shoot formation. The development of induced buds into shoots occurred on WPM medium containing kinetin. Vigorous shoots larger than 2.0 cm in length were successfully rooted in half strength WPM medium supplemented with 1.0 mg dm^-3 indole-3-butyric acid.

Responses of wheat (Triticum aestivum L.) to various concentrations of NaCl and levels of drought were followed. With the rise of NaCl or drought, or NaCl and drought together, growth was retarded. The water content of shoots and roots was mostly unchanged. The chlorophyll and carotenoid contents were increased in plants subjected to salinity or drought or both. Only high salinity level induced a considerable decrease in net photosynthetic rate (P_N) and dark respiration rate (R_D). P_N and R_D were decreased with the decrease of soil moisture content. The content of Na⁺ in the shoots and roots of wheat plants increased with increasing salinity or decreasing soil moisture content or both treatments. Considerable variations in the content of K⁺, Ca²⁺ or Mg²⁺ were induced by the NaCl, drought or both treatments.

Root excision fromTriticum vulgare L. var.muticum seedlings induced a membrane potential drop, homeostasis disturbances, and loss of absorbing capacity in roots. During subsequent 3 - 4 h incubation the initial physiological properties of the roots were restored. At that period K⁺absorption could be blocked by tetraethylammonium (TEA) without changing pH of the incubation medium. After 5 - 6 h of incubation the membrane hyperpolarization and the enhancement of the absorbing capacity were observed. At that period K⁺ influx, at presence or absence of valinomycin in incubation medium, was coupled with acidification of the external medium and was not blocked by TEA.

Plastochron index (PI) in two genotypes of cowpea (Vigna unguiculata L. Walp) showed a remarkable sensitivity to water stress. A linear expression PI = 4.6179 + 0.7451 S (r² = 0.93) summarised the degree of sensitivity and predictability of PI to different stress levels (S). PI could be regarded as a stress sensitive trait in cowpea.

The effect of NaCI stress on the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH) and glutamate synthase (GOGAT) in callus lines ofVigna radiata which differ in salt resistance, was studied at weekly intervals upto 28 d of growth. After 28 d, the NaCI resistant callus (selected at 300 mM NaCI) at NaCI concentrations higher than 200 mM maintained higher NR activity than non-selected line. NaCI stress also affects aminating and deaminating activities of GDH. The NADH-GDH activity in the presence of NaCI was higher in the resistant than non-selected line. On the other hand, NAD-GDH activity in both the lines was completely inhibited after 7 d of growth. The increased activity of NADH-GDH in resistant calli may play a vital role in protecting the cells from toxic effect of increased endogenous level of ammonia which probably accumulates due to efficient NO₃ ^- reduction. NADH-GOGAT activity was found to decrease under salt stress in both the callus lines. Nitrogen assimilation in salt-resistant calli under salt stress was found to be characterized by high NR and NADH-GDH activities, concomitantly with low GOGAT activity.

Copper caused bleaching of phycocyanin changing the pigment-protein interaction. On cadmium treatment the energy was not efficiently transferred to photosystem (PS) 2 and a spillover of energy occurred to PS1. Thallium treatment induced a general decrease in absorption and fluorescence of chlorophyll and phycobilisomes, whileAnacystis was resistant to lead.

An investigation was carried out on chickpea (Cicer arietinum L.) cv. C-235 inoculated withRhizobium sp.Cicer strain cv 4 Az^r. Nodule functioning was monitored at 15 d intervals starting from 45 days after sowing (DAS) and inoculation in order to study nodule development and senescence under natural and stress conditions (dark treatments of 18 and 66 h). Maximum rate of N₂-fixation was observed between 50 - 60 DAS. After this acetylene reducing activity (ARA) fell and it was negligible 75 DAS. This decline in ARA with ageing of plants and nodules was accompanied by a decline in leghemoglobin content and greening of the nodules. When 60 % of the nodule tissue had turned green 75 DAS, a sharp increase in nodule peroxidase activity (3.7 fold) was observed whereas the catalase activity was reduced by 50 % in comparison with the control. The glutathione-reductase and ascorbate-peroxidase activity followed a trend parallel to that in N₂-fixation, but the variation was much smaller. The changes in the total soluble carbohydrates, cytosolic proteins and nitrogen content per se were not expressive. Dark treatments induced premature senescence of the nodules as was evident from the marked decrease in ARA. However, the decline in leghemoglobin content was relatively small as compared to ARA. The changes in cytosolic proteins, total soluble carbohydrates, peroxidase activity, catalase activity, glutathione reductase activity and ascorbate peroxidase activity of nodules under dark-induced nodule senescence were almost parallel to those observed under natural senescence.

The effect of irradiance on the ratio of variable to maximum fluorescence (F_v/F_m) and on the anthocyanin content of chilled (0.5 °C) young maize plants was investigated after returning the plants to a non-chilling temperature (25 °C). Compared to control plants grown throughout at 25 °C in the light, the F_v/F_m hardly changed during chilling or when returned to a non-chilling temperature in the dark, but there was a decrease in this parameter if the plants were shifted to the light after the cold treatment. Similarly, compared to the control plants there was no change in the anthocyanin content either at low temperature or after transfer to 25 °C in the dark. However, there was a sudden increase in the anthocyanin level after returning the plants from dark cold conditions to a non-chilling temperature in the light.

Reserves of twig nitrogen of drought-deciduous species changed seasonally and provided some of the nitrogen required for canopy reconstruction after drought relief. By contrast, in evergreen species, nitrogen mobilization from old leaves and use in expanding leaves occurred simultaneously at the time of leaf exchange and twig nitrogen remained constant

Changes in various components of photosynthetic apparatus during the 4 d dark incubation at 25°C of detached control and ultraviolet-B (UV-B) treatedVigna unguiculata L. leaves were examined. The photosynthetic apparatus was more degraded in younger control seedlings and for a longer time UV-B treated seedlings than in the older or for a shorter time UV-B treated seedlings. This was shown by determining the losses in chlorophyll (Chl) and protein contents, variable fluorescence yield, photosystem (PS) 2, PS1 and ribulose-1,5-bisphosphate carboxylase (RuBPC) activities, and photosynthetic¹⁴CO₂ fixation. In contrast, the Car/Chl ratio increased during the dark incubation due to less expressed degradation of Car.

Dry mater, water content, water, osmotic and pressure potentials, content of saccharides and potassium were measured duringin vitro cultivation ofVitis rootstocks. Three cases were compared: a) the micro-cuttings with normal growth; b) micro-cuttings which stop their growth after 15 d of culture, and c) micro-cuttings reactivated by 6 d of continuous darkness.
Major differences were observed in water content and osmotic potential. The stopping of growth was not a specific property of buds, but was probably due to restriction of translocation of saccharides and water in the shoot.

Difluoromethylornithine (DFMO) counteracted several processes that are promoted or inhibited by auxins or inhibitors of polar auxin transport: inhibition of asymmetric gene expression in carrot, stimulation of gametic embryogenesis inBrassica, inhibition of root elongation in tobacco, inhibition of the development of lateral roots in pea and adventitious roots in apple, and inhibition of floral bud formation inArabidopsis