No abstract

The effects of the plant growth retardant tetcyclacis on in vitro tuber formation in potatoes was studied, using two different approaches : 1 . tuber formation in various lines that did not or hardly form tubers under control conditions, and 2 . tuber formation by the variety Bintje, which readily forms tubers . The ABA-deficient (droopy) lines of S. phureja hardly formed tubers without the addition of tetcyclacis . In the presence of this growth retardant tuberization was nearly 100%, within three weeks of in vitro culture, even in the absence of cytokinin . A series of somatic hybrids between S . tuberosum and S. brevidens, that did not form tubers in field and pot experiments, were tested . They all formed tubers in vitro in the presence of tetcyclacis . Stoloniferous shoots formed on single-node cuttings from in vitro grown Solanum tuberosum var Bintje plantlets were transferred to media containing a high level of sucrose . In the presence of tetcyclacis, tuber formation started after 4 days, reaching a maximum level of 80% at day 7 . Tubers formed in the presence of tetcyclacis, accumulated starch and expressed several tuber-specific genes . These effects were fully antagonized by gibberellic acid . It is concluded that the growth retardant tetcyclacis is a potent tool in the study of tuber formation in potatoes .Abbreviations : ABA = abscisic acid; BAP = benzylaminopurine ; GA3 = gibberellic acid ; STS = silver thiosulphate ; TET = tetcyclacis . 257

The effect of methyl jasmonate (MJ) vapors on the composition and peroxidation of major fatty acids in the organs of common buckwheat seedlings was investigated. The composition of fatty acids in the hypocotyl and cotyledons of seedlings changed significantly under exposure to MJ vapors in closed jars. Four-day exposure to MJ led to a significant reduction in the concentrations of stearic, linoleic, and linolenic acids in the hypocotyl, whereas oleic acid levels increased approximately 3.5-fold. A decrease in stearic acid levels and an increase in the content of linolenic acid were noted in cotyledons, whereas oleic acid levels decreased in roots. Seven-day exposure to MJ vapor caused a further reduction in stearic acid content and an increase in oleic acid and linoleic acid levels in the hypocotyl. At the same time, the linoleic acid content of roots and linolenic acid levels in cotyledons were doubled, but a 5-fold reduction in linolenic acid concentrations was observed in roots. Methyl jasmonate intensified fatty acid peroxidation in cotyledons after 4 and 7 days and in roots after 4 days of exposure. Peroxidation was inhibited in the hypocotyl and roots after 7 days. The noted changes in the composition and peroxidation of fatty acids are probably indicative of senescence in buckwheat seedlings under the influence of MJ. Senescence seems to proceed faster in cotyledons than in other organs of buckwheat seedlings.

We examined the response of common buckwheat (<em>Fagopyrum esculentum</em> Moench) seedlings, as a nontarget plant, to various doses of glyphosate applied to the root zone or to the shoots. Glyphosate was used at 0.1, 0.5, and 1.0 mM concentrations. The study was conducted on seedlings grown in hydroponic cultures under controlled growth conditions. Primary root and shoot growth, anthocyanin and photosynthetic pigment contents were measured to assess the effects of exposure to glyphosate. Glyphosate applied to shoots had a considerably higher impact on the growth of primary roots and shoots of seedlings. Low glyphosate concentrations produced an increase in anthocyanin content of hypocotyls, regardless of the mode of its application. Increasing the concentration of glyphosate applied to the root zone resulted in a gradual increase in anthocyanin content in cotyledons. Our overall results show that in hydroponically grown common buckwheat seedlings, glyphosate is less phytotoxic when applied to the root zone than when applied to the shoot. Low doses of glyphosate applied to the root zone stimulate root and shoot growth and increase the anthocyanin levels in cotyledons. The phytotoxicity of glyphosate was decreased in the absence of mineral nutrients in the root zone of buckwheat seedlings.