In vitro flowering – A system for tracking floral organ development in Dendrocalamus hamiltonii Nees et Arn. ex Munro.

Dendrocalamus hamiltonii plants are slender and tall (15-25 m) thereby, rendering tagging, sampling and tracking the development of flowers difficult. Therefore, a reproducible system of in vitro flowering was established for tracking the stages of flower development. MS medium supplemented with 2.22 µM 6-benzylaminopurine, 1.23 µM indole-3-butyric acid and 2% sucrose was optimized as the flower induction medium (FIM) wherein 28 and 42 days were required for the development of gynoecium and androecium, respectively. Six distinct stages of in vitro flower development were identified, and the flowers were comparable with that of in planta sporadic flowers. Pollen viability of the in vitro flowers was higher than those of in planta ones. The in vitro system developed in the present study facilitates easy tracking of different stages of flower development under controlled environmental conditions. It can also be used for medium- or long-term storage of pollens and manipulation of in vitro fertilization.

Tolerancia experimental de las especies vegetales Nicotiana glauca, Jacaranda mimosifolia, Tecoma stans, Medicago sativa y Spinacea oleracea al boro, en Argentina

Experimental tolerance to boron of the plant species Nicotiana glauca, Jacaranda mimosifolia, Tecoma stans, Medicago sativa y Spinacea oleracea in Argentina. The activity of boron industries is a punctual and diffuse source of air, soil and water pollution. Therefore, it is a priority to study possible ways of reducing this impact. A relatively new technology for reducing soil pollution is phytoremediation, which uses plants and associate microorganisms. The first step in phytoremediation is to detect tolerant plant species, which is the objective of this work. A laboratory experiment to assess the germination, survival and growth of different species at different boron concentrations was carried out following a factorial design with two factors: plant species and boron concentration. Boron concentrations were determined at the beginning and the end of the experiment, taking into account substrates with and without vegetation. We found significant differences for treatment, species and the interaction species*treatment. N. glauca, M. sativa and J. mimosifolia were the most tolerant species. The other species had a decrease in the response variables, with the concentration of the pollutant. All the species had a low survival at the highest boron concentration. The reduction in boron concentration at the end of the experiment was higher in the 30 ppm treatment with M. sativa and the lower was registered in the 20 ppm treatment with J. mimosifolia and in 30 ppm with T. stans and S. oleraceae. We conclude that N. glauca, M. sativa and J. mimosifolia can be considered in remediation plans. Rev. Biol. Trop. 56 (3): 1053-1061. Epub 2008 September 30.

La actividad de las industrias borateras constituye una fuente puntual y difusa de contaminación del aire, suelo y aguas superficiales y profundas. Por lo tanto, el estudio y experimentación acerca de las posibles formas de contrarrestar este impacto constituye una prioridad. Una técnica relativamente nueva para descontaminar suelos es la fitorremediación, que emplea plantas y microorganismos asociados. El primer paso es detectar las especies vegetales tolerantes, lo que constituye el objetivo de este trabajo. Se realizó un experimento en laboratorio para evaluar la germinación, la supervivencia y el crecimiento de distintas especies en diferentes concentraciones de boro. Al comienzo y al final del experimento se determinó la concentración de boro en el sustrato para cada tratamiento y para sustratos con y sin vegetación. Se encontraron diferencias significativas debidas al tratamiento, la especie y la interacción especie *tratamiento. M. sativa, N. glauca y J. mimosifolia fueron las especies de mayor tolerancia al boro. Las otras especies presentaron una disminución en todas las variables-respuesta en función de la concentración del contaminante. Todas presentaron una baja supervivencia en la máxima concentración. La disminución de boro fue máxima en el tratamiento de 30 ppm de boro con M. sativa y la menor se registró en los tratamiento de 20 ppm de boro con J. mimosifolia y de 30 ppm de boro con T. stans y S. oleraceae. Se concluye que N. glauca, M. sativa y J. mimosifolia podrían considerarse como prometedoras en remediación.

Accumulation, tolerance and impact of aluminium, copper and zinc on growth and nitrate reductase activity of Ceratophyllum demersum (Hornwort).

Ceratophyllum demersum (homwort) was subjected to toxic concentrations of Al (3 and 9 mg l(-1)), Zn (3 and 9 mg l(-1)) and Cu (2.5 and 7 mg l(-1)) in culture solutions for 15 days. The higher dose of Al enhanced the chlorophyll content significantly (p<0.05) in the first 6 days of treatment while other treatments caused marked reductions. Nitrate reductase activity (NRA) was significantly reduced (p<0.05) byAl, Cu and Zn toxicity and ceased completely in plants treated with Cu by the 6th day of treatment. Dry biomass and relative growth rate were reduced significantly (p<0.05) by metal treatment. Tolerance index of the plant was low for Cu (21.62 and 13.43% at low and high doses, respectively) and moderate for Zn (63.74 and 54.85%) and Al (72.83 and 68.79%). Accumulation ofAl, Zn and Cu was threefold at higher doses compared with the lower doses but the bioconcentration factors (BCF) were very low indicating that this plant is not a hyper accumulator of these metals.

Biochemical parameters of plants as indicators of air pollution.

In the present study species like Mangifera indica, Linn., Cassia fistula, Linn., and Eucalyptus hybrid were exposed to different air pollution load for short duration (active biomonitoring). Variation in biochemical parameters like chlorophyll, protein, soluble sugar free amino acid, ascorbic acid, nitrate reductase, superoxide dismutase and peroxidase in the leaves were found to be pollution load dependent. These variations can be used as indicators of air pollution for early diagnosis of stress or as a marker for physiological damage to trees prior to the onset of visible injury symptoms. Just by analyzing these biochemical indicators air quality can also be assessed.

In vitro propagation of Acorus calamus Linn.--a medicinal plant.

High frequency in vitro propagation protocol was standardized from rhizome explants of A. calamus. Maximum shoot multiplication frequency was obtained on Murashige and Skoog's media supplemented with 4 mg/l 6-benzyl amino purine and 0.5 mg/l indole-3-acetic acid. Regenerated shoots were rooted in vitro or directly transferred to sterile soil and well developed roots were observed within two weeks. The rooted plants were successfully established in the field.

Micropropagation of terrestrial orchids, Anoectochilus sikkimensis and Anoectochilus regalis.

Two horticulturally important jewel orchids of the genus Anoectochilus were successfully micropropagated. Isolated nodes of A. sikkimensis collected from Sikkim in Eastern Himalayas and subsequently reared under nursery conditions and A. regalis collected from Western Ghats in Southern India were cultured for 12 weeks on Woody Plant Medium (WPM) to produce a maximum of 4.8 and 5.6 callus--free axillary shoots respectively at 95 and 98% efficiency. During reculture of the explants from in vitro raised shoots under the same conditions, the total number of shoots obtained from the nodes (21.4) and shoot tips (8.2) of A. regalis were significantly higher than those hardy and slow growing shoots of A. sikkimensis (12.3 and 4.3) respectively. Shoots (4-6 cm) were rooted in medium containing NAA (2.70 microM) and activated charcoal (0.2%). The rooted plants established at 95-98% rate in community pots after hardening. After 6 months, green house adapted community potted plants of A. regalis were transferred to natural forest habitat locally with 95 and 70% survival respectively after 12 months. The plants, established in community pots and native forest habitat were free from any morphological and growth defects.