Induction of direct somatic embryogenesis and plant regeneration in pepper (Capsicum annuum L.).

Pepper (cv. New Mexico - 6 and Rajur Hirapur) plants were regenerated from immature zygotic embryos via direct somatic embryogenesis. Somatic embryos were formed directly, without any intervening callus, on the zygotic embryo apex, embryo axis and cotyledons on Murashige and Skoog's (MS) medium containing 2,4-D (418 µM), thidiazuron (10 µM) and a high concentration of sucrose (6-10%). The best response was observed on MS medium containing 2,4-D (9 µM), coconut water (10%) and high sucrose (8%). The entire process of induction and maturation of the embryos was completed on the same medium. Histological examination indicated that secondary embryogenesis also occurred directly from the primary somatic embryos. Differentiation of embryos was nonsynchronous, and some embryos were swollen and distorted with fasciation. More than 70% of the mature normal somatic embryos germinated readily on MS medium containing GA3 or TDZ, alone and in combination, and following transfer to pots developed into normal plants.

Promotion ofin vitro shoot formation from excised roots of silktree (Albizzia julibrissin) by an oxime ether derivative and other ethylene inhibitors.

This report describes the regeneration response of excised seedling roots of silktree (Albizzia julibrissin) to added ethylene precursors/generators (1-amino-cyclopropane-1-carboxylic acid [ACC], 2-chloroethylphosphonic acid [CEPA]), biosynthesis inhibitors (aminoethoxyvinylglycine [AVG], an oxime ether derivative [OED={[(ispropylidene)-amino]oxy}-acetic acid-2-(methoxy)-2-oxoethyl ester], CoCl(2) [Co(++)]), and an ethylene action inhibitor (AgNO3 [Ag(+)]). When placed on B5 medium, about 50% of the control explants formed shoot buds within 15 days. Addition of ACC or CEPA (1-10 µM) to the culture medium decreased both the percentage of cultures forming shoots and the number of shoots formed per culture. In contrast, AVG and OED (1-10 µM) increased shoot formation to almost 100% and increased the number of shoots formed per culture. Likewise, both Co(++) and Ag(+) (1-10 µM) increased shoot regeneration, but the number of shoots produced after 30 days was less than with AVG or OED. The inhibitors of ethylene biosynthesis were partially effective in counteracting the inhibitory effect of ACC on shoot formation. These results suggest that modulation of ethylene biosynthesis and/or action can strongly influence the formation of adventitious shoots from excised roots of silktree.

In vitro production of flowering shoots in 'German Red' carnation: effect of uniconazole and gibberellic acid.

Callus regenerated near the base of senescing petals of flower bud explants of 'German Red' carnation (Dianthus caryophyllus L.) produced adventitious flowering microshoots on MS-medium containing benzylaminopurine (8.9 µM) and naphthaleneacetic acid (2.7 µM). When these microshoots were subcultured with some callus, additional adventitious flowering microshoots were produced from the callus. The production of adventitious flowering shoots continued for many subcultures spanning a period of more than two years. Uniconazole (6.9 µM) increased the number of adventitious shoots formed by as much as two-fold but decreased shoot length by about 50%. In contrast, GA3 (2.9 µM) decreased adventitious shoot formation and increased shoot length. Regardless of the growth regulator treatment, virtually all of the adventitious shoots produced flower buds. Thus, the growth regulators influenced flowering only indirectly by altering the number of adventitious shoots produced in vitro. These results demonstrate that the flowering habit of the adventitious shoots of 'German Red' carnation is highly persistent and the flowering stimulus continues to be transmitted to the newly formed microshoots through the callus.

Effect of gibberellin biosynthesis inhibitors on shoot regeneration from hypocotyl explants of Albizzia julibrissin.

Hypocotyl explants of Albizzia julibrissin were placed on Gamborg's B5 medium supplemented with various levels of paclobutrazol, uniconazole, prohexadione calcium, or GA3. Callus formation was evident within one week after placement of the explants on the culture media. Green nodule-like structures protruded from the distal end of the explants within 10 days and developed into shoots within a month. These shoots readily formed adventitious roots when placed on fresh culture medium. All three of the gibberellin biosynthesis inhibitors increased shoot formation compared to the control. The number of shoots per explants was increased 107, 79, and 168% by 0.3-0.4 µM paclobutrazol, uniconazole, and prohexadione calcium, respectively. In contrast to the gibberellin biosynthesis inhibitors, GA3 decreased shoot formation. These results indicate that modification of gibberellin status can have a strong impact on the number of shoots formed.

Influence of growth regulators on somatic embryogenesis, plantlet regeneration, and post-transplant survival of Echinochloa frumentacea.

After placement on Murashige and Skoog's basal medium supplemented with 3-5 mg/l 2,4-D, immature inflorescence expiants of Echinochloa frumentacea gave rise to three distinct types of callus: a) loosely arranged and soft; b) compact and translucent; c) compact, sticky and mucilaginous. Somatic embryo formation occurred in type 'b' callus in about 18-24 d. Callus types 'a' and 'c' did not produce somatic embryos. The highest percentage of cultures exhibiting somatic embryogenesis occurred on the medium containing 5 mg/l 2,4-D and 0.5 mg/l kinetin. Somatic embryos also formed directly on the inflorescence (without intervening callus formation) in about 15% of the expiants placed on this medium. The addition of paclobutrazol or uniconazole (0.25 or 1 mg/l) to the medium had no influence on the percentage of cultures exhibiting direct somatic embryogenesis, but paclobutrazol slightly increased the mean number of somatic embryos per culture. Many of the callus-derived somatic embryos germinated when subcultured on basal MS medium supplemented with kinetin. Addition of paclobutrazol or uniconazole to the culture medium at 0.25 or 1 mg/l decreased somatic embryo germination and shoot elongation but increased root length and leaf width. Both paclobutrazol and uniconazole increased survival of the plantlets following transplanting to soil. Increased post-transplant survival was accompanied by reduced water loss from plantlets produced on culture media containing triazoles.

Influence of 2-(3,4 dichlorophenoxy)-triethylamine on photosynthesis of Phaseolus vulgaris L.

The effect of foliar sprays of the growth regulator 2-(3,4 dichlorophenoxy)-triethylamine (DCPTA) on net photosynthesis (Pn) by intact bean plants depended upon concentration and the stage of development of the leaves. A single foliar spray of 2.0 mM DCPTA reduced Pn when applied to young expanding leaves but had little effect on fully expanded leaves. Lower DCPTA concentrations (0.2 to 0.8 mM) had no effect on Pn, unless applied more than once which resulted in reduced Pn. The DCPTA-induced inhibition of Pn was associated with chlorosis and aberrations in chloroplast ultrastructure. DCPTA did not affect stomatal resistance. When applied to detached leaf disks in the dark, DCPTA retarded the normal loss of chlorophyll suggesting that DCPTA may have anti-seneseent properties.

The photosynthetic pathway types of some desert plants from India, Saudi Arabia, Egypt, and Iraq.

Plants collected from different habitats in the deserts of India, Saudi Arabia, Egypt, and Iraq were screened for their photosynthetic CO2-fixation pathways using δ13C and δD values. The analyses comprised 128 species belonging to 108 genera and 46 families. Neither the C4 nor the CAM pathway was prevalent in the plant families analyzed except in Poaceae, where C4 metabolism absolutely dominated. Of 93 dicotyledonous plants, only 10 exhibited a C4 pathway and only 2 were CAM plants. The study shows that some species reported by other workers as C4 plants are clearly C3 ones.

Effect of phosphon-D on photosynthetic light reactions and on reactions of the oxidative and reductive pentose phosphate cycle in a reconstituted spinach (Spinacia oleracea L.) chloroplast system.

Phosphon-D (tributyl-2, 4-dichlorobenzylphosphonium chloride), known as an inhibitor of gibberellin biosynthesis, enhances photosynthetic electron transport by up to 200%, with Fe(CN) 6 (3-) and NADP(+) being the electron acceptors. Maximum stimulation is reached at phosphon-D concentrations around 2-5 µM. At the same time photosynthetic ATP formation is gradually inhibited. Phosphon-D concentrations over 0.1 mM inhibit electron transport. The uncoupling activity of phosphon-D is manifested by inhibition of noncyclic ATP synthesis and by stimulation of light-induced electron flow. The inhibition of ATP synthesis drastically decreases photosynthetic carbon assimilation in a reconstituted spinach chloroplast system. The two ATP-dependent kinase reactions of the reductive pentose phosphate cycle become the rate-limiting steps. On the other hand a stimulated photoelectron transport increases the NADPH/NADP(+) ratio, resulting in a drastic inhibition of chloroplast glucose-6-phosphate dehydrogenase (EC 1.1.1.49), the key enzyme of the oxidative pentose phosphate cycle. When light-induced electron flow is inhibited by high phosphon-D concentrations and the NADPH/NADP(+) ratio is low, the light-dependent inhibition of glucose-6-phosphate dehydrogenase is gradually abolished.

Additive and synergistic effects of kinetin and ethrel on germination, thermodormany, and polyribosome formation in lettuce seeds.

The inhibition of germination of Grand Rapids lettuce (Lactuca sativa L.) seeds at 35 C was removed to a marked extent by kinetin and 2-chloroethylphosphonic acid (ethrel). When both compounds were used together, an additive effect was observed. A synergistic effect was, however, noted when ethrel promoted the kinetin reversal of abscisic acid inhibition of seed germination (light- as well as gibberellic acid-, induced). Both kinetin and ethrel increased the total ribosomal material and the percentage of polyribosomes in lettuce seeds imbibed in the light for 24 hours. A combination of the two compounds showed a synergism in polyribosome formation only at high ethrel concentration. The inability of ethrel to reverse abscisic acid inhibition indicates that kinetin action cannot always be substituted by ethrel. The possible mechanisms involved in the enhanced response by a combination of kinetin and ethrel are discussed.

Eco-physiological studies on Indian arid zone plants : V. A. Screening of some species for the C4-pathway of photosynthetic CO2-fixation.

Plants of the Indian desert belonging to 29 families, 85 genera and 105 species of angiosperms were screened for the possible occurrence of the C4-pathway of photosynthetic CO2-fixation. The criteria used for screening were leaf anatomy and/or δ13C values. The results indicated the occurrence of the C4-pathway in members of 3 new families (Acanthaceae, Cleomaceae, Scrophulariaceae), 10 new genera (Aerva, Anticharis, Blepharis, Elyonurus, Glossocardia 1 , Gynandropsis, Melanocenchris, Sehima, Sesuvium, Zalaeya) and 34 new species of the angiosperms. All the grasses investigated were found to possess the C4-pathway. Cuscuta hyalina, a phloem-parasite, growing on C4 hosts (Tribulus, Zalaeya) also revealed δ13C value very close to that found in the host plants.

[Studies on the influence of abscisic acid and gibberellic acid on the activities of some enzymes of carbohydrate metabolism in leaves of Pennisetum typhoides seedlings]. / Untersuchungen über den Einfluß von Abscisin- und Gibberellinsäurebehandlung auf die Aktivitäten einiger Enzyme des Kohlenhydratstoffwechsels in Blättern von Pennisetum typhoides Keimlingen.

Abscisic acid (ABA) and gibberellic acid (GA3), alone and in combination, were applied to Pennisetum typhoides seedlings and the effects on the activity of phosphorylase, amylase, invertase, hexose-phosphate-isomerase, sucrose-6-phosphate-synthetase and sucrose-synthetase were studied. ABA-treatment inhibited the activity of amylase and invertase, but stimulated greatly that of phosphorylase, hexose-phosphate-isomerase, sucrose-6-phosphate-synthetase and sucrose-synthetase. GA3 alone, on the other hand, promoted the activity of invertase but had no significant influence on the other enzymes tested. Given in combination with ABA, GA3 completely overcomes the stimulative effect of ABA on sucrosesynthetase.

Eco-physiological studies on Indian arid zone plants : III. Effect of sodium chloride and gibberellin on the activity on the enzymes of carbohydrate metabolism in leaves of Pennisetum typhoides.

Seedlings of Pennisetum typhoides were grown in sodium chloride (NaCl) and gibberellic acid (GA3) separately and in combination, and the effects on the activity of amylase, phosphorylase, aldolase, invertase, hexose-phosphateisomerase, sucrose-synthetase and sucrose-6-phosphate-synthetase were studied. Treatment of the seedlings with NaCl caused an inhibition of the activity of amylase and invertase in the leaf homogenate, but enhanced that of phosphorylase, aldolase, sucrose-synthetase and sucrose-6-phosphate-synthetase. GA3 alone, as observed earlier, promoted the activity of invertase but indicated no significant influence on the other enzymes tested. In combination with salt, however, GA3 tended to counteract, partially or wholly, the effect of NaCl on the activity of several enzymes tested. The possible significance of the similarities between the action of abscisic acid (ABA) and salinity in influencing growth and metabolism of plants during stress is discussed.

Eco-physiological studies on Indian arid zone plants : I. Photosynthetic characteristics of Pennisetum typhoides (Burm. f.) Stapf & Hubbard and Lasiurus sindicus Henr.

Photosynthetic characteristics of two important grasses of Indian desert have been studied. Pennisetum typhoides, an important cereal crop, known to have 'Kranz'-type leaf anatomy and low CO2-compensation point, shows the C-4-dicarboxylic acid pathway for photosynthetic carbon reduction. Lasiurus sindicus, a promising forage grass, has also been shown to possess, for the first time, a typical 'Kranz'-type leaf anatomy and a very similar CO2-fixation pattern like Pennisetum typhoides. It is remarkable that both species after short time exposure to 14CO2 show a high labelling not only in malate but also in alanine. This may be due to the activity of an aspartic acid decarboxylase.

Eco-physiological studies on Indian arid zone plants : II. Effect of salinity and gibberellin on the activity of the enzymes of amino-acid metabolism in leaves of Pennisetum typhoides.

The separate and combined effects of sodium chloride and gibberellin (GA) on growth and the activities of alanine aminotransferase (GPT), aspartate aminotransferase (GOT) and glutamate dehydrogenase (GLDH) have been studied in the aerial parts of Pennisetum typhoides seedlings. Salt concentrations higher than 8.55×103 M inhibited growth and reduced GLDH activity, but strongly stimulated the activity of GPT and, to a lesser extent, that of GOT. GA alone, on the other hand, stimulated growth but did not affect activity of any of the enzymes tested. In combination with salt, however, GA tended to counteract the effect of salt on both growth and enzyme activity. The possible significance of the results in explaining adaptation of plants under conditions of stress has been discussed.

Morphactin-kinetin interaction in lettuce seed germination and seedling growth.

Butylester of morphactin (n-butyl-9-hydroxy-fluorence-(9)-carboxylate) greatly inhibited seed germination and seedling growth of two strains of lettuce, "Attraktion" and "Hohlblättriger Butter". The inhibitory effect of morphactin on seed germination was completely overcome by kinetin but the latter chemical was ineffective in reversing the morphactin induced inhibition of seedling growth. Thus it appears probable that the two substances effect seedling growth independently.