Yasseen Mohamed-Yasseen

The role of seed coats in seed viability

The seed coat is the seed’s primary defense against adverse environmental conditions. A hard seed coat protects the seed not only from mechanical stress but also from microorganism invasion and from temperature and humidity fluctuations during storage. Phenolic compounds in the seed coat contribute to seed hardness and inhibition of microorganism growth. During germination, the seed coat protects the seed from hydration stress and electrolyte leakage.ResumenLa cubierta de la semilla es la defensa primaria contra el medio ambiente adversa. Una cubierta dura proteja la semilla no solo de tensión mecanica sino también de ana invasion de microorganismos y de cambios en temperatura y humedad durante almacenaje. Los phenolics en la cubierta de la semilla contribuyan a la dureza de la semilla y la inhibitión de crecimiento de microorganismos. Durante la germinatión, la cubierta proteja la semilla de la tension de hidratación y del escape de electrolytes.

In vitro shoot proliferation and production of sets from garlic and shallot

A procedure is described to regenerate shoots and bulbs in vitro with high frequency from shoot tips of garlic and shallot plants using benzyladenine or thidiazuron. Regenerated shoots were induced to form bulbs in Murashige and Skoog medium (1962) containing 5 g l-1 activated charcoal and 120 g l-1 sucrose under a long-day photoperiod. Bulbs formed in vitro were transferred to soil without acclimatization and produced viable plants. This method could be useful to produce low-cost bulbs, which are easy to handle and store until needed.

Rapid propagation of tuna (Opuntia ficus-indica) and plant establishment in soil

Explants from young joints of mature plants of tuna (Opuntia ficus-indica Mill.) were cultured on Murashige and Skoog (MS) medium containing 8.8 μM benzyladenine (BA) and 0.5 μM naphthaleneacetic acid (NAA). Shoots produced were utilized as secondary explants. Each shoot was cut longitudinally from apex to base into two explants, and some of these explants were cut transversely into proximal and distal explants. The size and number of shoots produced was affected by size and position of the explant within its source. The shoots were rooted in vitro or ex vitro and plants were successfully established in soil from both rooting methods.

In vitro shoot proliferation and propagation of guava (Psidium guajava L.) from germinated seedlings

Guava seeds were germinated on Murashige and Skoog (MS) medium with or without 8.8 μM benzyladenine (BA). BA increased the rate of germination and the number of lateral shoots (3.4 vs 1.2 per seedling). Stem nodes from these lateral shoots were cultured on proliferation media with 4.4 μM BA, and multiple shoots (3.5) were formed within 4 weeks of culture. Increasing the concentration of BA or the addition of naphthaleneacetic acid (NAA) did not affect shoot formation. Shoots produced from explants and lateral shoots from germinated seedlings were rooted in media containing activated charcoal (AC) or 9.8 μM indolebutyric acid (IBA). Shoots rooted with IBA had a higher rooting percentage (100% vs 75%) and a greater number of roots (5.5 vs 3.2) but the shoots were shorter (2.6 vs 3.4 cm) than when rooted in AC, and they required an additional 4 weeks of culture in media with AC to achieve shoot elongation. About 80% of the shoots with roots survived in the glasshouse and produced normal phenotypic plants.

Influence of agar and activated charcoal on uptake of gibberellin and plant morphogenesis in vitro

SummaryAgar and activated charcoal (AC) are commonly used in tissue culture. However, their deeper actions and functions are largely unknown. This experiment investigated the effect of agar and AC, singly and jointly, on gibberellin (GA) uptake by corn shoots. Corn seeds were germinated on Murashige and Skoog medium (MS). Shoot excised from 1-wk-old seedlings were cultured on liquid (0.0 g l−1 agar) or solid (8 g l−1 agar) MS containing 3 μM indole-3-acetic acid, 13.3 μM N6-benzyladenine, and 6000 CPM ml−1 [3H]GA4 as tracer. Both liquid and solid media had two treatments, one without AC and one supplemented with 5 g l−1AC. Uptake of [3H]GA4 and morphogenesis of corn shoots were recorded after 2 wk of culture. Corn explants cultured in AC-free media acquired high levels of [3H]GA4, while explants from AC-containing media showed only traces of [3H]GA4. Explants cultured in AC-free liquid medium contained about twice the amount of [3H]GA4 as those from AC-free solid medium. Addition of agar reduced shoot length, while addition of AC increased both shool and root length. It is concluded that: (1) agar reduced the uptake of GA4; and (2) GA4 was irreversibly adsorbed by AC, and thus became unavailable to corn explants.

Micropropagation of pitaya (Hylocereus undatus Britton et rose)

SummaryA procedure for micropropagation of pitaya using thidiazuron (TDZ) and naphthaleneacetic acid (NAA) is described. Explants were excised from young joints of mature plants and cultured on Murashige and Skoog medium (MS) containing 0.5 μM NAA and 0.5 μM TDZ. Shoots produced from these first explants were cut up to produce secondary explants, either by decapitation or by longitudinal division into three parts. The decapitated and longitudinal explants were cultured on MS supplemented with 0.5 μM NAA and either 0.01, 0.09, 0.5, or 0.9 μM TDZ. Decapitated explants produced more shoots at higher frequency that the longitudinal explants. For both types of secondary explants, most shoots were developed from the distal parts. Shoots produced from secondary explants were rooted in MS and then transferred to soil where they produced normal plants.

In vitro bulb production from Allium spp

SummaryA procedure for bulb formation from onion, garlic, and shallot explants is described. Explants from cut stem bases were cultured in shoot induction medium composed of Murashige and Skoog (MS) medium with or without N6-benzyladenine. Shoots produced were then transferred to bulb induction medium composed of MS medium containing 5 g/liter activated charcoal and 120 g/liter sucrose under a long-day photoperiod and 28° C. Bulbs were also produced from onion and garlic directly, without passing through shoot formation, when explants were cultured in the bulb induction medium described above. Bulbs were transferred to soil without acclimatization and produced viable plants.

In vitro regeneration, flower and plant formation from petiolar and nodal explants of culantro (Eryngium foetidum L.)

SummaryA procedure for plant regeneration, flower and plant formation from petiolar and inflorescence nodal explants of culantro is discribed. Leaf petioles were excised from young leaves of non-flowering plants while nodal explants were excised from the inflorescence. Explants were cultured in Murashige and Skoog (MS) medium alone or supplemented with 0.5μM naphthaleneacetic acid (NAA) and 0.9, 1.8, 4.5, or 9 μM thidiazuron (TDZ). All explants produced multiple shoots. In addition, nodal explants formed flowers. Shoot number, flower number and shoot length were influenced by TDZ and NAA. Rooted shoots from both types of explants were transferred to soil where plants were successfully established.

In vitro shoot proliferation and plant regeneration from kurrat (Allium ampeloprasum var. kurrat) seedlings

Shoots were produced from kurrat seedling and mature plant explants cultured in Murashige and Skoog medium (MS) alone or supplemented with 4.4 μM benzyladenine (BA). Shoots were also produced from explants through a two-step procedure. Regenerated shoots were induced to form roots on MS medium with 5 g I-1 activated charcoal. Plants were successfully established in soil.

In vitro multiplication and plantlet establishment of avocado

SummaryA procedure is described to regenerate shoots and plants from the embryonic axis of avocado seedlings with benzyladenine or thidiazuron. Explants were grown in the dark for 10 d and then transferred to an 18-h photoperiod to induce multiple shoots. Increased concentrations of benzyladenine or thidiazuron resulted in increased shoot production. Shoots were transferred to shoot promoting media where additional shoots were formed. Under the best conditions, six rooted shoots were produced per original explant. About 80% of the shoots with roots survived in the glasshouse and produced normal phenotypic plants.