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Christianson, Michael L.; Duffy, Stephen H.
doi: 10.1007/s003440010062pmid: N/A
Plant growth regulators now include more than the classic examples auxin, cytokinin, ethylene, and gibberellin, but little is known about the activity of these additional classes of molecules in nonvascular plants. The formation of buds by protonema of the moss Funaria hygrometrica is perhaps the best known and most fully characterized developmental system in the nonvascular plants. Examination of the effects of exogenously supplied salicylic acid and acetylsalicylate on this bioassay system shows that salicylates can regulate growth and development in mosses, producing a dose-dependent inhibition of bud formation. Other experiments show that this action is distinct from any direct effect on the well-known cytokinin stimulation of bud formation, occurs late in the process of bud formation, occurs prior to the stable commitment of nascent buds, and is not an effect on the outgrowth of young shoots. Because mosses are the sister clade to the vascular plants, these results suggest that the ability to perceive and transduce salicylate signals is an ancient feature of land plant physiology.
Suzuki, T.; Tomita-Yokotani, K.; Yoshida, S.; Takase, Y.; Kusakabe, I.; Hasegawa, K.
doi: 10.1007/s003440010060pmid: N/A
A mixture of oligogalacturonic acids, the partial degradation substances of polygalacturonic acid, promoted shoot growth in cockscomb (Celosia argentea L.) seedlings, which generally had a high sensitivity for growth-promoting substances. The effect of the mixture of oligogalacturonic acids on shoot growth of cockscomb was higher than that of the polygalacturonic acid at concentrations above 30 ppm. These oligomers were loaded onto an anion exchange column, DEAE Sephadex A-25, and separated into individual oligomer sizes using the NH4HCO3 eluent system. This separation method has the advantage of using NH4HCO3 as the eluent solution; NH4HCO3 in the sample solution is effectively removed by lyophilization. Each of the isolated oligogalacturonic acids gave a single band on a fluorophore-assisted carbohydrate electrophoresis (FACE), and they showed the m/z value which corresponded to their molecular ion peaks [M-H]- on a fast atom bombardment mass spectrometry (FAB-MS) analysis. These results showed that the successive chromatography method used in this study is well suited for the preparation of oligogalacturonic acid for the plant growth test. Furthermore, we showed that the effective degree of polymerization (DP) of oligogalacturonic acid was around 8 on shoot growth of cockscomb seedlings, and the effects of both smaller and larger oligogalacturonic acids were slightly lower than that of octa-galacturonide. Octa-galacturonide promoted shoot growth of cockscomb at concentrations above 10 mM, and showed a 66% promotion at the most effective concentration of 300 mM. Root growth was slightly inhibited at concentrations above 300 mM. These results suggest that DP around 8 of oligogalacturonic acids has the function to control shoot growth in cockscomb as a growth-promoting substance.
Maciejewska, Beata ; Kopcewicz, Jan
doi: 10.1007/s003440010061pmid: N/A
The effect of methyl jasmonate (JA-Me) on the floral bud formation and elongation growth in the short-day plant Pharbitis nil was investigated. The placing of 4-day-old seedlings of P. nil in a solution of JA-Me for a period of 24 h before an inductive (16 h or 14 h of darkness) night led to a dramatic reduction in the number of flower buds formed by the plant. Plants treated with JA-Me also totally lost their capacity to form a generative terminal bud. JA-Me applied after photoinduction does not inhibit flowering. Gibberellic acid (GA3) partly reverses the inhibitory effect of JA-Me. Plants treated simultaneously with JA-Me and GA3 formed about 3flower buds more than plants treated with JA-Me only. JA-Me at a concentration of 10-7 M stimulates slightly, but at higher concentrations it inhibits root growth and shoot growth. A distinct lack of correlation between the effect of JA-Me on inhibition of flowering and shoot and root growth was noted. This indicates the independent action of JA-Me in controlling both processes.
Chen, Shaoliang ; Li, Jinke ; Wang, Tianhua ; Wang, Shasheng ; Polle, Andrea ; Hüttermann, Aloys
doi: 10.1007/s00344-002-1001-4pmid: N/A
We designed two experiments to investigate the osmotic stress and ion-specific effects on xylem abscisic acid (ABA) and the relevance to salinity tolerance in one-year-old seedlings of Populus euphratica Oliv. (a salt-resistant genotype) and one-year-old rooted cuttings of P. 'popularis 35-44' (P. popularis) (a salt-sensitive genotype). Net photosynthetic rates (Pn) and unit transpiration rates (TRN) of the two genotypes were significantly decreased upon osmotic shock caused by PEG 6000 (osmotic potential = -0.24 MPa) or iso-NaCl (50 mM). Shoot xylem ABA concentrations in both genotypes increased rapidly after the onset of PEG stress, resulting from a decreased water flow. NaCl-treated trees of P. euphratica maintained considerably greater concentrations of ABA than PEG-treated plants in a longer term, whereas salinized P. popularis exhibited a transient accumulation of ABA in the shoot. TRN was greatly enhanced in both genotypes when pressure (0.24 MPa) was applied to counteract the osmotic suction of 50 mM NaCl. Pressurizing of root systems diluted solutes in the root xylem, but the dilution effect was more pronounced in P. popularis. Root xylem ABA concentrations in P. euphratica steadily increased with salt stress although pressurization lowered its levels. In contrast, there were no observed changes in ABA response to salinity in pressured P. popularis. Therefore, we concluded that the salt-tolerant P. euphratica had a greater capacity to synthesize ABA under saline conditions, which may partially result from specific salt effects. In addition, P. euphratica exhibited a higher capacity for salt (Na+ and Cl-) transport control under salt stress, compared with P. popularis. The possible association between ABA and salt transport limitation, and the relevance to salinity tolerance were discussed.
Gómez-Cadenas, Aurelio ; Arbona, Vicent ; Jacas, Josep ; Primo-Millo, Eduardo ; Talon, Manuel
doi: 10.1007/s00344-002-0013-4pmid: N/A
This paper describes the physiological effects of abscisic acid (ABA) and 100 mM NaCl on citrus plants. Water potential, leaf abscission, ethylene production, photosynthetic rate, stomatal conductance, and chloride accumulation in roots and leaves were measured in plants of Salustiana scion [Citrus sinensis (L) Osbeck] grafted onto Carrizo citrange (Citrus sinensis [L.] Osbeck × Poncirus trifoliata [L.] Raf) rootstock. Plants under salt stress accumulated high amounts of chloride, increased ethylene production, and induced leaf abscission. Stomatal conductance and photosynthetic rates rapidly dropped after salinization. The addition of 10 mM ABA to the nutrient solution 10 days before the exposure to salt stress reduced ethylene release and leaf abscission. These effects were probably due to a decrease in the accumulation of toxic Cl- ions in leaves. In non-salinized plants, ABA reduced stomatal conductance and CO2 assimilation, whereas in salinized plants the treatment slightly increased these two parameters. The results suggest a protective role for ABA in citrus under salinity.
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