USING LIMITED INDUCTIVE PHOTOPERIOD FOR SCHEDULING COSMOS BIPINNATUS AND TAGETES TENUIFOLIA

Plants of Cosmos bipinnatus Cav. ‘Sensation’ (a quantitative short-day plant) were grown under continuous conditions favorable or unfavorable for flowering, and some plants in each group were treated with gibberellic acid (GA3). Floral apices of Cosmos are formed by the transition of previously vegetative apices. The vegetative apex shows a cytohistological zonation pattern superimposed upon a tunica–corpus organization. The vegetative apex passes into an intermediate stage presumed typical of many plants held under non-inductive conditions. This stage is marked by many cytological features characteristic of both reproductive and vegetative apices but leaves continue to be produced. The presence of the intermediate stage accounts for conflicting results obtained in physiological studies since there is great variation in response rate depending on age of plant and the stage of the apex at the start of an experiment. This stage is followed by a typical transitional stage marked by an increase in RNA content, increased mitotic activity, and a change in zonation. Elongation of the apex and internodes occurs followed by initiation of the involucral bracts and floret primordia, marking the beginning of the prefloral and inflorescence stages respectively.GA3 specifically induces Cosmos to flower under non-inductive conditions thereby influencing floral initiation in a facultative short-day plant. Microscopic examination of the rate of apical transition revealed that GA3 substituted effectively for short days but was not as efficient an inducer as were short days.

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Nectar feeding behavior of some butterflies in the botanical garden of Dhaka university

Bangladesh Journal of Zoology ◽

10.3329/bjz.v42i1.23339 ◽

2015 ◽

Vol 42 (1) ◽

pp. 85-90

Author(s):

Murshida Begum ◽

Ummey Habiba ◽

Moksed Ali Howlader

Keyword(s):

Feeding Behavior ◽

Corolla Tube ◽

Botanical Garden ◽

Tagetes Erecta ◽

Butterfly Species ◽

Tephrosia Purpurea ◽

Nectar Feeding ◽

Cosmos Bipinnatus ◽

Eurema Hecabe ◽

Highly Correlated

Nectar feeding behavior of butterflies belonging to the families Nymphalidae, Danaidae, Pieridae, Lycaenidae and Papilionidae were studied in the Botanical garden of Dhaka University. The highest and the lowest duration of searching time was 39 ± 2 and 36 ± 5 seconds respectively for the Catopsila pomona and Zizina otis. The highest and the lowest duration of feeding was 13.0 ± 1 and 9.9 ± 0.9 seconds respectively for the Danaus chrysippus and Zizina otis. The longest proboscis (12.6 ± mm) was recorded in Danaus chrysipus. The deepest corolla (22 ± 5mm) was found in the flower of Cosmos bipinnatus plants. The proboscis of 4 butterfly species named Eurema hecabe, Jononia almana, Catochrysopes strabo and D. chrysipus was highly correlated with the corolla tube of Cosmos bipinnatus, Tephrosia purpurea and Tagetes erecta repectively.Bangladesh J. Zool. 42(1): 85-90, 2014

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FLORAL INITIATION IN THE LONG-DAY PLANT Rudbeckia hirta

HortScience ◽

10.21273/hortsci.26.6.719a ◽

1991 ◽

Vol 26 (6) ◽

pp. 719A-719

Author(s):

Richard L. Harkess ◽

Robert E. Lyons

Keyword(s):

Methyl Green ◽

Floral Initiation ◽

Serial Sections ◽

Sodium Cacodylate ◽

Rudbeckia Hirta ◽

Long Day ◽

Cacodylate Buffer ◽

Ethanol Series ◽

Inductive Photoperiod ◽

Short Days

A study was undertaken to determine the rate of floral initiation in Rudbeckia hirta. R. hirta plants were grown to maturity, 14-16 leaves, under short days (SD). Paired controls were established by placing half of the plants under long days (LD) with the remainder left under SD. Beginning at the start of LD (day 0), five plants were harvested daily from each photoperiod group for twenty days. Harvested meristems were fixed in 2% paraformaldehyde - 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.0) for 24 hrs, dehydrated in an ethanol series, embedded in paraffin and sectioned at 8 μm. Serial sections were stained with Methyl-green Pyronin, with adjacent sections treated with RNase for nucleic acid comparison. All events of floral initiation were identified, The results of limited inductive photoperiod indicate that 16-18 LD were required for flowering.

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