Influence of Different Cytokinins on the Germination of Lettuce (<i>Lactuca sativa</i>) and Celery (<i>Apium graveolens</i>) Seeds

Biddington, N. L.; Thomas, T. H.

doi:10.1111/j.1399-3054.1976.tb01865.x

Cited by 24 publications

(15 citation statements)

References 19 publications

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“…A role for cytokinins in germination is not unprecedented. It has been shown that cytokinin levels in germinating seeds exhibit transient spikes that are timed closely with the initiation of germination (4,24,47). Since the miaA mutant of M. extorquens, in whose medium there was no detectable cytokinin, stimulated germination at a level indistinguishable from the level stimulated by the wild type, a role for cytokinins in this process is unlikely.…”

Section: Discussionmentioning

confidence: 95%

tRNA Is the Source of Low-Level trans- Zeatin Production in Methylobacterium spp

2002

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Pink-pigmented facultatively methylotrophic bacteria (PPFMs), classified as Methylobacterium spp., are persistent colonizers of plant leaf surfaces. Reports of PPFM-plant dialogue led us to examine cytokinin production by PPFMs. Using immunoaffinity and high-performance liquid chromatography (HPLC) purification, we obtained 22 to 111 ng of trans-zeatin per liter from culture filtrates of four PPFM leaf isolates (from Arabidopsis, barley, maize, and soybean) and of a Methylobacterium extorquens type culture originally recovered as a soil isolate. We identified the zeatin isolated as the trans isomer by HPLC and by a radioimmunoassay in which monoclonal antibodies specific for trans-hydroxylated cytokinins were used. Smaller and variable amounts of trans-zeatin riboside were also recovered. trans-Zeatin was recovered from tRNA hydrolysates in addition to the culture filtrates, suggesting that secreted trans-zeatin resulted from tRNA turnover rather than from de novo synthesis. The product of the miaA gene is responsible for isopentenylation of a specific adenine in some tRNAs. To confirm that the secreted zeatin originated from tRNA, we mutated the miaA gene of M. extorquens by single exchange of an internal miaA fragment into the chromosomal gene. Mutant exconjugants, confirmed by PCR, did not contain zeatin in their tRNAs and did not secrete zeatin into the medium, findings which are consistent with the hypothesis that all zeatin is tRNA derived rather than synthesized de novo. In germination studies performed with heat-treated soybean seeds, cytokinin-null (miaA) mutants stimulated germination as well as wild-type bacteria. While cytokinin production may play a role in the plant-PPFM interaction, it is not responsible for stimulation of germination by PPFMs.Although the best-studied plant-bacterium relationships involve pathogenesis or symbiosis, plants interact constantly with phylloplane bacteria and with the bacteria in the soil around their roots (rhizosphere). While it is not widely believed that epi-and endophytic bacteria have overt effects on plants, there is evidence (13) that plants interact with pink-pigmented facultatively methylotrophic bacteria (PPFMs), which are inhabitants of the phylloplane and rhizosphere. PPFMs are gram-negative members of the alpha subclass of the class Proteobacteria that belong to the genus Methylobacterium and are known to inhabit the leaf surfaces of a wide variety of plant species (11). One intriguing aspect of the plant-PPFM relationship is the possibility that PPFMs may provide cytokinins to the plant host or have cytokinin-like effects. Corpe and Basile (12) demonstrated that callus from Streptocarpus prolixus (gracilis) (Cape primrose) regenerated plantlets within 15 days when it was cultured cobiotically with PPFMs. PPFM-free controls exhibited no plant development after 30 days. However, Corpe and Basile did not indicate whether specific phytohormone regimens could mimic the PPFM effects or whether PPFMs produce phytohormones. We demonstrated previously that heat ...

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Section: Discussionmentioning

confidence: 95%

tRNA Is the Source of Low-Level trans- Zeatin Production in Methylobacterium spp

2002

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“…The quantitative and qualitative responses of plants to d i f f e r e n t C K s , s u c h a s k i n e t i n ( K i n ) a n d benzylaminopurine (BAP), may differ considerably. Thomas et al (1975) and Biddington and Thomas (1976) demonstrated that BAP is more active than any other CK in germination, as well as in breaking the dormancy of celery and lettuce seeds. The possible involvement of CKs in responses to adverse environmental conditions has also been suggested (Hare et al 1997;Brault and Maldiney 1999).…”

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confidence: 96%

Presowing Seed Treatment with Cytokinins and Its Effect on Growth, Photosynthetic Rate, Ionic Levels and Yield of Two Wheat Cultivars Differing in Salt Tolerance

Iqbal

Ashraf

2005

J Integrative Plant Biology

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The effects of presowing seed treatment with different concentrations of cytokinins (kinetin and benzylaminopurine; 100, 150, and 200 mg/L) on growth, photosynthetic capacity, and ion homeostasis were investigated in two spring wheat (Triticum aestivum L.) cultivars, namely MH-97 (salt sensitive) and Inqlab-91 (salt tolerant). Primed and non-primed seeds were sown in a field in which NaCl salinity of 15 dS/m was developed. Of the different concentrations of priming agents tested, the effect of a moderate concentration of kinetin (150 mg/L) was very pronounced, particularly in improving growth and grain yield, in both cultivars. In addition, priming with kinetin alleviated the adverse effect of salt stress on gaseous exchange characteristics (net CO 2 assimilation rate and water use efficiency) in both cultivars. Seed priming with a moderate concentration of kinetin also altered the pattern of accumulation of Na + and Cl -in the shoots, irrespective of the wheat cultivar, under conditions of salt stress. However, all other priming agents at the different concentrations tested did not show any consistent effect on ion levels, except hydropriming, which increased K + levels in the shoots of both cultivars under salt stress. In conclusion, a moderate concentration of kinetin showed a consistent effect in altering the growth and grain yield of both wheat cultivars, which was related to the beneficial effects of kinetin priming on water use efficiency and photosynthetic rate under conditions of salt stress.

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“…Therefore, the differences in structure are likely to affect the function of the cytokinin. For example, Biddington and Thomas (1976) demonstrated that BA is more active than any other cytokinin in increasing germination rate, and in breaking dormancy of celery and lettuce seeds.…”

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Seed enhancement with cytokinins: changes in growth and grain yield in salt stressed wheat plants

2006

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Cytokinins are often considered abscisic acid (ABA) antagonists and auxins antagonists/synergists in various processes in plants. Seed enhancement (seed priming) with cytokinins is reported to increase plant salt tolerance. It was hypothesized that cytokinins could increase salt tolerance in wheat plants by interacting with other plant hormones, especially auxins and ABA. The present studies were therefore conducted to assess the effects of presowing seed treatment with varying concentrations (100, 150 and 200 mg l -1 ) of cytokinins (kinetin and benzylaminopurine (BAP)) on germination, growth, and concentrations of free endogenous auxins and ABA in two hexaploid spring wheat (Triticum aestivum L.) cultivars. The primed and non-primed seeds of MH-97 (saltintolerant) and Inqlab-91 (salt-tolerant) were sown in both Petri dishes in a growth room and in the field after treatment with 15 dS m -1 NaCl salinity. Both experiments were repeated during 2002 and 2003. Among priming agents, kinetin was effective in increasing germination rate in the salt-intolerant and early seedling growth in the salt-tolerant cultivar when compared with hydropriming under salt stress. Thus, during germination and early seedling growth, the cytokinin-priming induced effects were cultivar specific. In contrast, kinetin-priming showed a consistent promoting effect in the field and improved growth and grain yield in both cultivars under salt stress. The BAP-priming did not alleviate the inhibitory effects of salinity stress on the germination and early seedling growth in both cultivars. The increase in growth and grain yield in both cultivars was positively correlated with leaf indoleacetic acid concentration and negatively with ABA concentration under both saline and non-saline conditions. The decrease in ABA concentration in the plants raised from kinetinprimed seeds might reflect diminishing influence of salt stress. However, the possibility of involvement of other hormonal interactions is discussed.

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Influence of Different Cytokinins on the Germination of Lettuce (Lactuca sativa) and Celery (Apium graveolens) Seeds

Cited by 24 publications

References 19 publications

tRNA Is the Source of Low-Level trans- Zeatin Production in Methylobacterium spp

tRNA Is the Source of Low-Level trans- Zeatin Production in Methylobacterium spp

Presowing Seed Treatment with Cytokinins and Its Effect on Growth, Photosynthetic Rate, Ionic Levels and Yield of Two Wheat Cultivars Differing in Salt Tolerance

Seed enhancement with cytokinins: changes in growth and grain yield in salt stressed wheat plants

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