Tissue culture of ornamental pot plant: A critical review on present scenario and future prospects

Hormones in plants differ from most of those in animals by having pleiotropic effects; that is, they are involved in the control of a wide range of developmental processes. At the same time the effect of a hormone on any developmental process depends on the species. For example, ethylene inhibits growth in dicotyledons and most monocotyledons but is promotory in deepwater rice and other hydrophytes. Moreover, two or more hormones can interact synergistically or antagonistically in many circumstances. Equally, any given hormone may affect the biosynthesis or metabolism of another, thus affecting endogenous levels. The issue is further complicated by the fact that environmental factors e.g. light, water status, wounding, pathogens may modify responses and indeed hormone levels themselves. The reason for this appears to be that hormones (and growth regulators) and environmental factors share many components in their transduction chains (i.e. the very early events which occur after the signal abiotic or biotic is perceived by the plant tissue). These transduction chains interact to produce an integrated response.

Plant Growth Regulators II: Cytokinins, their Analogues and Antagonists

Photosynthesis and carbon metabolism were followed during the acclimatization of micropropagated Spathiphyllum cv. Petite shootlets cultured with two different sucrose concentrations (3 and 6%). Increased sugar supply resulted in inhibition of photosynthesis, nonfunctional photosynthetic reaction centers, a more mixotrophic metabolism and higher starch and sucrose reserves at the end of the in vitro period. During the first days of acclimatization, net photosynthesis and adenosine diphosphoglucose (ADPG) pyrophosphorylase (EC 2.7.7.27) activity decreased for both treatments. In this period, sucrose was mainly used as nutrient reserve by plants cultured on 6% sucrose, as evidenced by a strong increase in sucrose synthase (EC 2.4.1.13) activity together with a severe decline in sucrose content. In the same period, sucrose breakdown and synthesis were in balance for plants cultured on 3% sucrose and the starch content increased slightly. After one week plants started to recover and full photosynthetic capacity developed. Two weeks after ex vitro transplantation, no differences between plants micropropagated with 3 or 6% sucrose could be found for photosynthesis, carbohydrate pools or enzyme activities. At the end of acclimatization the starch content increased again.

Impact of sugar concentration in vitro on photosynthesis and carbon metabolism during ex vitro acclimatization of Spathiphyllum plantlets

In this study, we analysed morphological, anatomical and physiological effects of polyploidisation in Spathiphyllumwallisii in order to evaluate possible interesting advantages of polyploids for ornamental breeding. Stomatal density was negatively correlated with increased ploidy level. Stomatal size increased in polyploids. Tetraploid Spathiphyllum plants had more ovate and thicker leaves. The inflorescence of tetraploids had a more ovate and thicker spathum, a more cylindrical spadix and a thicker but shorter flower stalk. Biomass production of the tetraploids was reduced, as expressed by lower total dry weights, and tetraploids produced fewer shoots and leaves compared with their diploid progenitors. Furthermore, tetraploid Spathiphyllum plants were more resistant to drought stress compared with diploid plants. After 15 days of drought stress, diploids showed symptoms of wilting, while the tetraploids showed almost no symptoms. Further, measurements of stomatal resistance, leaf water potential, relative water content and proline content indicated that the tetraploid genotypes were more resistant to drought stress compared with the diploids.

Influence of ploidy level on morphology, growth and drought susceptibility in Spathiphyllum wallisii

In vitro ecology: Exogenous factors affecting growth and morphogenesis in plant culture systems

In vitro propagation of spathiphyllum

Lateral shoot tips from young Asparagus setaceus (Kunth) Jessop (syn. A. plumosus Baker) shoots were grown on a modified Murashige and Skoog medium. Tips from 5 to 20 mm lateral shoots had significantly better growth and development than tips from lateral shoots (2 mm) still covered by leaf-scale. The optimum temperature for growth and development of the explants was 17 to 24°C. The initial growth was fast at 24°C but stopped after about 4 weeks. At 17°C the growth was slow but in return the cultures continued to grow. Kinetin was necessary for growth. Without any kinetin all cultures died. Optimum growth was found with 2 mg/l kinetin. There was no growth at all with IAA alone. A low IAA concentration had no effect, but at high concentrations IAA inhibited the kinetin induced growth.

Development of Asparagus plumosus Shoot Tips Grown in vitro

Lateral shoot tips from young shoots of Asparagus setaceus (Kunth) Jessop (syn. A. plumosus Baker) were grown on a modified Murashige and Skoog medium. PBA was the most effective cytokinin for growth and development of Asparagus plumosus shoot tips. The optimal range of PBA was between 0.02 and 2 mg/1. Zeatin was less effective, and kinetin, BA and 2iP were poor as cytokinins for A. plumosus. The optimal temperature for growth and development was 21°C. There was interaction between the temperature and the PBA concentration. With increasing temperature from 17 to 24°C the need for PBA increased from 0.2 to 2 mg/1.

Anne Fonnesbech

Papers

In vitro propagation of spathiphyllum

Development of Asparagus plumosus Shoot Tips Grown in vitro

Influence of Cytokinins and Temperature on Development of Asparagus plumosus Shoot Tips in vitro