Browsing by Author "Siju Thomas, T."

Now showing 1 - 10 of 10
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Gas exchange parameters and canopy area in relation to coconut productivity in two agroclimatic regions of India
    (2008-01) Siju Thomas, T.; Naresh Kumar, S.; Vinu K. Cherian; Rajagopal, V.
    Coconut (Cocos nucifera L.) palms exhibit variation in productivity across different agro-climatic regions of India. It is important to study the factors contributing to such variation in order to increase the productivity of palms. The present study was intended to elucidate the physiological basis of yield variability in coconut across different agro-climatic regions. With this objective, seasonal variations in leaf gas exchange parameters and morphological and dry matter production characteristics of four coconut cultivars were studied at two different agro-climatic regions. Results indicated variation in gas exchange parameters of cultivars with seasons and with regions suggesting genotype-environment interactions. Overall net photosynthetic rates were higher in cultivars grown at Western ghats-hot sub humid per humid region (Kidu). Palms growing at Eastern coastal plains-hot sub humid region (Veppankulam), on the other hand, maintain greater water use efficiency. The results also indicate that, under dry conditions both stomatal and non-stomatal factors impose limitations to photosynthesis in coconut. The physiological efficiency coupled with superior morphological characters such as a larger canopy, and favourable climatic conditions for a longer period, in addition to the soil type at Veppankulam region enabled the palms to attain more of their potential productivity.
  • Thumbnail Image
    Item
    Identification and Characterization of in Situ Drought Tolerant Palms in Farmers Fields in Different Agro-Climatic Zones
    (2002) Naresh Kumar, S.; Rajagopal, V.; Siju Thomas, T.; Vinu K. Cherian; Hanumathappa, M.; Anil Kumar; Srinivasulu, B.; Nagvekar, D.
    Coconut palms are mainly grown as rainfed crop, and are exposed to drought of different intensities and durations in various parts of the country. It is important to identify and conserve the ecotypes, which could withstand the vagaries of nature and still performed better in terms of growth and yield. Such efforts will ensure that the natural genetic variability and desirable traits are identified and conserved for further exploitation. With this in view present survey was undertaken in farmers fields at different agro-climatic zones, viz., Western coastal area - hot sub-humid-per-humid (Ratnagiri - Maharastra), hot semi arid (Arisikere - Karnataka) and Eastern coastal plains- hot sub-humid (Ambajipeta- Andhra Pradesh), which represent the major coconut growing areas in India. These places faced periodical durought during last 15 years and the dry spell was longer in Ratnagiri (216 days) and Arsikere (202 days). During survey drought affected and apparently tolerant palms were selected based on morphology. The data indicate that in situ drought tolerant palms had more number of leaves, bunch and mature nuts compared to the affected palms. Gas exchange characters were also high in apparently tolerant palms. These palms also exhibited good water use efficiency. However, the biochemical composition did not show any definite trend between tolerant and susceptible types. The superiority of these palms in the photosynthetic parameters showed their capacity for drought tolerance and high yield. The tolerant palms can be used as mother palms in breeding programme for drought tolerance.
  • Thumbnail Image
    Item
    Influence of media composition on gas exchange parameters, biochemical composition and zygotic embryo-cultured coconut (Cocos nucifera L.) plantlets
    (2006-06) Naresh Kumar, S.; Anitha Karun; Siju Thomas, T.; Muraleedharan, K.; Parthasarathy, V.A.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Role of certain biochemical compounds in adaptation of coconut to different weather conditions - A study in two agro-climatic regions of India
    (2006-03) Siju Thomas, T.; Naresh Kumar, S.; Vinu K. Cherian; Kasturi Bai, K.V.; Rajagopal, V.
  • Thumbnail Image
    Item
    Stability Analysis For Dry Matter Production And Yield Components Of Coconut In Two Agroclimatic Regions Of India
    (2005) Siju Thomas, T.; Rajagopal, V.; Naresh Kumar, S.; Arunachalam, V.; Vinu K. Cherian
  • Thumbnail Image
    Item
    Stress responsive proteins in coconut seedlings subjected to water, high-light, flooding and high-temperature stresses
    (2007-12) Naresh Kumar, S.; Kasturi Bai, K.V.; John George; Balakrishnan, A.; Siju Thomas, T.
    Coconut seedlings of different cultivars and cross combinations were subjected to stresses like water, high temperature and flooding stresses independently. Results indicated increase in the concentration of heat stable protein fraction (HSPF) in leaf tissue even when the total protein concentration reduced due to stress. The percentage of HSPF in leaf tissue increased with decrease in leaf water potentials. Quantitative changes in proteins also we& observed in leaf and root tissue due to temperature and flooding. In HSPF, proteins of -66KDa are found in root and leaf tissue. Leaflet tissues have specific in the range ~10 and ~14 KDa which are not present in the root tissues. Two extra proteins 66 KDa and ~76 KDa appeared in water stressed WCT seedlings. They were also present in seedlings exposed to high light intensity (~1,500 mmol/m2/S) apart from an extra LMW HSP of 14.4 KDa. Among the MMW- proteins, protein of 53 KDa is present in all WCT samples. The LMW protein of 20.1 KDa, present in non-stress seedlings disappeared during water stress period. In temperature induced and flooded leaflet tissue, new proteins (LMW range ~17 KDa) were observed. In temperature induced root tissue, a protein band in the range of 30 KDa was observed but not in flooded root or in control root. Results indicate quantitative and qualitative variations in stress proteins in coconut seedlings subjected to different abiotic stresses.
  • Thumbnail Image
    Item
    Variations in nut yield of coconut and dry spell in different agro-climatic zones of lndia
    (2007-09) Naresh Kumar, S.; Rajagopal, V.; Siju Thomas, T.; Vinu K. Cherian; Ratheesh Narayanan, M.K.; Ananda, K.S.; Nagawekar, D.D.; Hanumanthappa, M.; Vincent, S.; Srinivasulu, B.
    Coconut is the major perennial crop in coastal areas of lndia. It is mainly grown under rainfed conditions in areas of high rainfall. However, these plantations face summer drought situations as the rainfall distribution is restricted to only 4 to 5 months a year, leaving remaining period as dry. The objective of the study is to quantify the dry spell and to deduce the influence of rainfall and dry spell on the nut yield in major coconut growing areas situated in different agro-climatic zones of India. viz., western coastal area - hot sub-humid per-humid (represented by Kasaragod in Kerala and Ratnagiri in Maharashtra), Western Ghats - hot sub-humid per-humid (represented by Kidu in Karnataka); hot semi-arid (represented by Arsikere in Karnataka); and eastern coastal plains - hot subhumid (represented by Veppankulam in Tamil Nadu and Ambajipeta in Andhra Pradesh). Variation in annual rainfall was from a maximum of 3337.7 mm (Kasaragod) to a minimum of 718.23 mm (Arsikere). Dry spell was longer in Ratnagiri (216 days) and Arsikere (202 days), and shorter at Kidu (146 days). The annual nut yield under rainfed conditions varied from 68 (Ambajipeta) and 66 (Kasaragod) to 41 (Arisekere) and 30 (Kidu). Impact of variations in dry spell on nut yield was discernible from the study. In view of the long duration (44 months) between the inflorescence initiation to nut maturation, the occurrence of dry spell in any one year would affect the yield for the subsequent three to four years. It can be inferred that the longer dry spell affects the nut yield for next four years to follow with stronger impact on fourth year, irrespective of the total rainfall.
  • Thumbnail Image
    Item
    Weather data based descriptive models for prediction of coconut yield in different agro-climatic zones of India
    (2009-03) Naresh Kumar, S.; Rajagopal, V.; Cherian, V.K.; Siju Thomas, T.; Sreenivasulu, B.; Nagvekar, D.D.; Hanumanthappa, M.; Bhaskaran, R.; Vijayakumar, K.; Ratheesh Narayanan, M.K.; Amarnath, C.H.
    Weather variables play an important role in determining the coconut palm growth, development and yield. The influence of weather on nut yield in coconut starts from inflorescence initiation and lasts till nut maturity (44 months). Historical data on weather variables and coconut nut yield from different agro-climatic zones viz., Western coastal area – hot sub-humid-per-humid (Kasaragod – Kerala; Ratnagiri – Maharastra), hot semi-arid (Arisikere – Karnataka) and Eastern coastal plains- hot sub-humid (Veppankulam- Tamil Nadu; Ambajipeta- Andhra Pradesh) of India were used for developing models for prediction of coconut yield. The prediction models with 3- and 4-year lag had high R2 values. The models differed for usage of parameters in different agro-climatic zones, indicating the relative importance of these parameters in respective conditions for realizing the nut yield in coconut. Interestingly, the parameters used in models for western coastal area – hot sub-humid-per-humid are temperature and relative humidity, as indicated even in the classification of these areas. Models were verified for 2 years and prediction of yield during 1998-99 and 1999-2000 within 10% confidence level validated these models. The study indicates that the relative humidity and temperature play important role during the ontogeny of inflorescence and nut development. The descriptive models, developed based on weather data, can be used for prediction of coconut yield two to four years in advance with in acceptable range of accuracy. The yields to be realized can be bracketed within predicted range obtained from models using one, two, three, and four year lags. These models can also be used for prediction of coconut nut yield in the situations similar to those in the present study.