S. N. Gogoi , S. K. Sarma

Abstract

Ecological investigation covering phyto-sociological attributes of 123 winter weed species have been reported in the article from the tea fields of Dibrugarh and Tinsukia districts of Assam. Importance Value Index (IVI) of each species was calculated. Among the weed species, Axonopus compressus (38.986), Imperata cylindrica (26.353), Ageratum conyzoides (26.251), Cynodon dactylon (14.383), Oxalis corniculata (11.348) and Gnaphalium indicum (10.39), are identified as the most dominant species in the tea fields. The study showed variation in their IVI values in different study sites due to for change in the physicochemical properties of soil of the study sites. Although the physical properties of soils are almost similar in all the study sites, their nutrient contents show variations, which may be the prime cause of variation in the IVI values.

Keywords

Winter Weeds, Tea Plantations, Assam

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S. N. Gogoi , S. K. Sarma

Abstract

The present study presents the weed flora of the tea gardens, occurring in the Dibrugarh and Tinsukia districts of Assam. The study revealed the occurrence of 165 weed species of which 39 were monocotyledonous, 112 dicotyledonous and 14 pteridophytic. Of these, 40 species were found during the winter season, 48 during summer season while 43 species during both winter and summer season. 18 weed species were very common and grown in all sites during the summer and winter seasons. 130 species were annuals and 35 were perennials. 133 species found to be reproduced by seeds, 31 species by seeds and vegetative organs, 8 species reproduced only by vegetative organ. Two pteridophytic species reproduced through spores and 12 species reproduced by spores and vegetative organs. Monocotyledonous (13.56 to 17.47%) and pteridophytic (2.4 to 12.42%) species occurred more in the summer than the winter season. 31 exotic weed species successfully established in the tea gardens of Assam.

Keywords

Weed Flora, Tea Plantations, Dibrugarh and Tinsukia Districts, Assam

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S. K. Sarma , K. Mazumder

Abstract

Different morpho-anatomical characters of Celltella asiatica in response to diverse habitat conditions of Assam have been reported. The climate of Assam is generally of sub-tropical type influenced by northeast monsoon, with neither too cold in the Wintel-nor too hot in summer. Assam's soils have been classified into the following three types-red loamy, lateritic and alluvial. Site Santipur, Gauhati University campus, Barpeta and Mangaldoi are made up of alluvial soil cover, whereas Sivasagar is capped by red loamy soil. Results showed significant correlation among morpho-anatomical characters of C. asiatica with soil nutrients concentration. Magnesium concentration was positively correlated with flower size. High p^H levels increase the leaf size by releasing important ions like potassium. Negative relationship was obtained between soil phosphorous concentration and flower size. Calcium concentration increased inflorescence size. Soil nutrients also affect some anatomical features of C. asiatica. High soil nitrogen concentration showed thinner epidermal layers and high soH calcium increased the thickness of hypodermal layers.

Keywords

Centeua Asiatica, Morpho-anatomy, Habitat, Soil

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