In vitro Culture of Medicago arborea L. Anthers: Initial Response

Abstract

High production of viable somatic embryos was obtained from cultured anthers in the second phase of meiosis, using microscopic level observations of tetrads. The medium with the greatest embryogenic efficiency was H6, composed of Murashige and Skoog (MS) medium with 2 mg l À1 of 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg l À1 of kinetin. All (100%) of the somatic embryos obtained germinated and produced 63% green and 37% albino seedlings. In general, embryogenic calli had a higher ion concentration than non-embryogenic calli, with the exception of calcium whose concentration was higher in non-embryogenic calli. The calli induced in the different media differed in their sucrose and starch compositions. The most embryogenic medium H6-induced calli with the highest sucrose concentration and the lowest starch concentration, before visible embryos were observed. In the leaves of the albino seedlings, sucrose concentrations were very high while those of starch were very low. Ion concentrations were also lower in albino plants than in the leaves of green seedlings, with the exception of calcium, whose concentration was higher. Most of the albino individuals were homozygous, even when their progenitors were heterozygous, thereby confirming their haploid nature.

Effects of the coordination mechanism between roots and leaves induced by root-breaking and exogenous cytokinin spraying on the grazing tolerance of ryegrass

“…This was demonstrated not only by the significant positive correlation between the ZR content and the biomass in the newly grown leaves, but also by the high ZR content giving rise to the high biomass in the newly grown leaves of the samples without root breaking, and of the samples sprayed with exogenous cytokinin. A number of researchers have also reported that the addition of benzylaminopurine increased the endogenous ZR content because benzylaminopurine was easily converted to ZR in plants (Ivanova et al 2006;Liu et al 2009); this was in agreement with our results. ZR is the main active form of cytokinin; thus, cytokinin is a key factor influencing the grazing tolerance of ryegrass.…”

Changes in endogenous cytokinin profiles in micropropagated Harpagophytum procumbens in relation to shoot-tip necrosis and cytokinin treatments

“…This indicates that exogenous application of CK does have an effect on the endogenous CK pool. The positive effects of applied CK on increasing the endogenous CK pool has been reported (Auer et al 1999;Vandemoortele et al 2001;Ivanova et al 2006). This increase in total CK pool was mainly due to high levels of 9-glucosides and to a lesser extent on O-glucosides in topolin-treated cultures (Tables 5, 8).…”

“…These reports suggest that the development of new shoots and roots might have triggered some physiological processes in plants lacking roots and shoot-tips due to STN thereby reinstating the physiological cross talk including CK transport, metabolism and signaling between the different plant parts. Positive correlation between an higher CK pool and hyperhydricity has been reported (Kataeva et al 1991;Ivanova et al 2006). These authors attributed the effect to either overproduction of CK and/or their accumulation resulting from an inability to use or metabolize them due to failed physiological processes such as CK signaling.…”

Effect of ammonium ions and cytokinins on hyperhydricity and multiplication rate of in vitro regenerated shoots of Aloe polyphylla

“…Chukwujekwu et al (2002) also reported that on MS medium (20.6 mM NH 4 + ) high levels of BA or zeatin did not improve shoot multiplication of A. polyphylla. Raising the concentration of exogenous BA and zeatin in the MS medium (20.6 mM NH 4 + ) had a positive effect on the accumulation of endogenous CKs in A. polyphylla shoots (Ivanova et al 2006), however this did not translate into a high multiplication rate.…”

“…However, many of these factors would only act to induce hyperhydricity when other conditions in the culture system are not optimised (Debergh et al 1992). A number of investigations have reported on the hyperhydricity-inducing tendency of exogenous cytokinins (CKs), usually in a concentration-dependent manner (Leshem et al 1988;Kataeva et al 1991;Williams and Taji 1991;Ivanova et al 2006). Large quantities of ammonium ions have also been shown to increase hyperhydricity in different species (Vieitez et al 1985;Daguin and Letouzé 1986;Brand 1993).…”