Pollination biology of Aristolochia tagala, a rare species of medicinal importance

Floral phenology, pollination biology and breeding system were studied in Aristolochia tagala Cham (Aristolochiaceae) grown under ex situ conditions. The flower exhibits structural features typical of fly-trap mechanism described for other Aristolochia species. Flowers show pronounced protogyny. Stigmas are receptive at anthesis and remain so for 24 h. Anthers dehisce 45– 48 h after anthesis by which time stigma receptivity is lost. Chironomid fly (Diptera) is the pollinator. Attracted by the odour and colour of the flower, the flies enter it and are detained in the chamber of the perianthtube (where the anthers and stigma are located) for nearly 50 h. Their escape is prevented by the presence of dense downward-pointing hairs in the perianth tube. The nectaries provide food to the insects. Following anther dehiscence, the thorax of the flies becomes loaded with sticky pollen grains. Hairs on the inner wall of the perianth tube wither and facilitate the exit of the flies. When a fly carrying the pollen load enters a fresh flower, it brings about pollination. Manual pollinations showed that the species permits geitonogamous pollination. The percentage of fruit set in manually pollinated flowers is higher than that resulting from open pollination, confirming that pollination is a limitation for fruit set in the ex situ-grown population. Nevertheless, fruit and seed set is sufficiently high for ex situ conservation purposes

Pollination biology of large cardamom (Amomum subulatum)

Amomum subulatum Roxb. (family Zingiberaceae) is the large cardamom of commerce cultivated in tropical wet evergreen forests of the Eastern Himalayas of India, Nepal and Bhutan. This study seeks to identify floral visitors and pollinators, examine floral adaptations for pollination and evaluate pollination efficiency. Studies were carried out in two flowering seasons (2005, 2006) in a 6-ha plantation located adjacent to a degraded reserve forest in the Sikkim part of the Himalayas. Only two flower visitor species, a bumble-bee (Bombus haemorrhoidalis Smith) and a honey bee species (Apis cerana F.) were recorded. The bumble-bee was the effective and only pollinator, but A. cerana was the pollen robber. Major flower adaptations for pollination by the bumble-bee are the length of the nectar tube, which is not accessible to short-tongued bees and a narrow passage in the fresh flower between the anther-stigma column and the labellum. The narrow passage forces the bumble-bee to push the anther-stigma column to enter the flower, which brings the body of the bumble-bee in contact with the anther and the stigma, and effects pollination. A. cerana does not come in contact with the stigma during pollen foraging and hence is unable to bring about pollination. Thus, structural features of the flower of A. subulatum differentiate the pollinator and the pollen robber. Pollination efficiency in the plantation was low due to the low population density of wild native pollinator, B. haemorrhoidalis

Structure and cytochemistry of the pistil in Arachis hypogaea

In Arachis hypogaea (Papilionoideae, Leguminosae), the stigma is of the dry papillate type. The papillae are multicellular and multiseriate. They are covered with a thin lining of pellicle which responds for proteins, non-specific esterases and acid phosphatases. The style is 3-6 cm long and hollow throughout its length. The stylar canal is bordered by a layer of canal cells. The canal cells in most of the stylar region are not glandular, they are vacuolate with scant cytoplasm. The canal cells at the base of the style, however, are glandular with dense cytoplasm and prominent nuclei. The structural features of the pistil of Arachis are discussed with those of other Papilionoideae

Contributions of Panchanan Maheshwari's school to angiosperm embryology through an integrative approach

P. Maheshwari who served as Professor and Head of the Department of Botany, University of Delhi from 1950 to 1966 built a flourishing school of embryology which became internationally recognized. His colleagues and students have contributed significantly to all areas of embryology through integrative approaches. In memory of his birth centenary year, we have prepared this article that summarizes the work done by his students and traces the phenomenal advances made in some areas in the post-Maheshwari era

Nutritional requirement at high-altitude with special emphasises to behaviour of gastro-intestinal tract and hormonal changes

When people are exposed to the extreme environmental conditions, such as high altitude (HA) where there is decrease in temperature and partial pressure of oxygen induces fatigue, insomnia, loss of appetite and increased cardiac output. Hence there is need to improve the appetite through the diet and digestion clout of the individual. In the present review paper we have discussed the efficiency of digestion is compromised at HA. Also about, Hypoxia, resulting by decreased partial pressure of oxygen can be classified into acute hypoxia and chronic hypoxia based on the exposure time. There is increased formation of reactive oxygen species (ROS) due to less oxygen available in the air at HA which leads to oxidative stress. Lipid peroxidation caused by oxidative stress. Hypoxia is mediated through hypoxia inducible factors which maintain oxygen haemostasis in the body. At HA diet rich in carbohydrates have been found to be beneficial as it increases glucose metabolism. Requirement of nutrients such as vitamin A, vitamin E and vitamin C as well as micronutrients such as zinc, iron, selenium, copper and manganese will be required at HA. Hypoxia effect on the intestine leads to malabsorption and the lipid storage is stimulated and lipid catabolism is inhibited through β-oxidation

Frugivorous bird diversity and their post-feeding behaviour in fruiting Syzygium cumini (Myrtaceae) in fragmented forests of central Western Ghats, India

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Apomixis and polyembryony in the guggul plant, Commiphora wightii

The present report is a part of our study on the reproductive biology of a traditional Indian medicinal plant,Commiphora wightii, a source of guggul steroids. Field examination showed a predominantly large number of isolated and groups of female individuals. Only one andromonoecious and two exclusively male plants were recorded. Female plants set seed irrespective of the presence or absence of pollen. Hand-pollination experiments and embryological studies have confirmed the occurrence of non-pseudogamous apomixis, nucellar polyembryony and autonomous endosperm formation for the first time in this plant, which is presently threatened by over-exploitation

Micropropagation of gum karaya (Sterculia urens) by adventitious shoot formation and somatic embryogenesis

Nodal explants from selected trees of gum karaya (Sterculia urens Roxb.) in the adult growth phase cultured on Murashige and Skoog (MS) medium supplemented with 6.62 μm N6-benzylaminopurine (BAP) produced an average of six adventitious shoots in 30 days. Shoots were rooted in vitro on 1/4-strength MS medium containing 9.82 μm indole-3-butyric acid. Nodulated callus was produced from hypocotyl explants cultured on MS medium supplemented with 4.52 μm 2,4-dichlorophenoxyacetic acid and 8.90 μm BAP. Somatic embryos developed when the nodulated callus was transferred to MS medium containing 0.45 μm thidiazuron (TDZ). TDZ treatment for 2 days gave the optimum response. Over 30% of the somatic embryos developed into plantlets when transferred to ¼-strength MS basal medium without any growth regulators. Plantlets produced from adventitious shoots and somatic embryos were acclimatized to ex vitro conditions and established in the field

Floral sexuality and breeding system in gum karaya tree, Sterculia urens

Comprehensive studies were carried out on phenology, floral sexuality, pollination biology, pollen-pistil interaction, breeding system and fruit and seed set on three populations of gum karaya tree (Sterculia urens). The species is andromonoecious and produces a large number of male and a limited number of bisexual (functionally female) flowers. The numbers of male and bisexual flowers varies not only between trees but also during the flowering period within a tree. Each male flower produces about 5000 fertile pollen grains. Neither in morphology nor in number, is there any difference between pollen grains in the bisexual and male flowers. However, pollen grains of bisexual flowers are completely sterile and incapable of siring any seeds. Their anthers, however, serve to attract pollinators; the emasculated bisexual flowers fail to do so. Thus S. urens is apparently andromonoecious but exhibits cryptic monoecy. That the species is self-incompatible was confirmed by controlled pollinations. The self-incompatibility is of the late-acting type and manifests after the entry of the pollen tube into the ovule. Apis indica is the only pollinator recorded by us and wind plays no role in pollination. The efficacy of pollination is low as only 56% of flowers were estimated to be pollinated. The pollen load on one-third the number of pollinated stigmas was lower than the number of ovules present. Fruit set under open pollination is poor and is highly variable from tree to tree (0.7-3.2%). Apart from pollination constraint, limited resource availability may also contribute to low fruit set

Carbon storage potential of shelter belt agroforestry system in northern transitional zone of Karnataka, India

Carbon sequestration has been suggested as a means to mitigate the increase in atmospheric carbon dioxide concentration. As agrisilviculture systems is one of the better options for stocking of carbon in plants and in soil. In the present study, carbon sequestration was quantified both biomass as well as in soil of agrisilviculture sys-tem six different tree species were selected such as, Pongamia pinnata, Dalbergia sissoo, Acacia auriculiformis, Tectona grandis, Casuarina equisitifolia, Azadirachta indica in shelterbelt of agroforestry system in arid region of Karnataka. Among six different tree species planted under shelterbelt, the growth performance with respect to gbh, height, clear bole height and basal area was highest in A. auriculiformis and A. indica. While maximum above ground biomass was observed in A. auriculiformis (59.75 t ha-1) followed by T.grandis (56.62 t ha-1), respectively. Whereas, below ground biomass was highest in T. grandis (20.25t ha-1) followed by A. auriculiformis (14.75t ha-1). Above ground carbon sequestration was highest in A. auriculiformis (13.30 t ha-1) followed by T. grandis (12.20 t ha-1), respectively. Whereas, below ground carbon sequestration was more in T. grandis (4.35 t ha-1) followed by A. auriculiformis (3.95 t ha-1). The Shelterbelt system sequestered 0.43 to 1.34% soil organic carbon stock in different depth. The carbon sequestered in different tree species was varying from 3.48 tons to 17.25 t ha-1.Growing tree crops in shelterbelts, bunds in the agroforestry systems will enhance accumulation of carbon stocking and provide additional benefits to the farmer’s income. It also regulates microclimate and increases the tree cover in agricultural field