Effect of Drip irrigation System on Physiology of Papaya  

P. Indhumathi1 , D. Durga devi1 , P. Jeyakumar1 , J. Auxcilia2
1. Department of Crop Physiology, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India
2. Department of Fruits, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India
Author    Correspondence author
International Journal of Horticulture, 2014, Vol. 4, No. 1   doi: 10.5376/ijh.2014.04.0001
Received: 20 Nov., 2013    Accepted: 25 Dec., 2013    Published: 02 Jan., 2014
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This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:

Indhumathi et al., 2014, Effects of Drip Irrigation Sysyems on Physiology of Papaya, International Journal of Horticulture, 2014, Vol.4, No.1 1-3 (doi: 10.5376/ijh.2014.04.0001)

Abstract

The Field experiment was conducted at College Orchard, HC&RI, Tamil Nadu Agricultural University and Coimbatore. The variety Pusa Dwarf was subjected to various levels of 100%, 80%, 60%, 40% evaporation replenishment at different growth stages of the crop. Higher content of relative water content (87.70%) and soluble protein (28.60 mg/g) and chlorophyll stability index (85.74%) thus expressed the higher response in nitrate Reductase activity (152.17 µmol CO2 m-2 s-1)at all stage of the crop.

Keywords
Evaporation replenishment; Soluble protein; Chlorophyll stability index; Nitrate; Reductase activity

Papaya (Carica papaya), the tropical fruit crop with higher production potential, is gaining much economic significance in India for the last two decades. The increasing demand of fruits in domestic market and papain in the export trade has made papaya cultivation extensive. The crop is cultivated in about 70,000 ha in India with an annual production of 1.68 million tones of fruits. In India, it is mainly grown in Madhya Pradesh, Andhra Pradesh, Bihar, Maharashtra, Tamil Nadu, Karnataka, Uttar Pradesh, West Bengal, Orissa etc.

Drip irrigation technology permits the efficient use of water and can help maximize the use of semi arid lands for agricultural use and this technology is particularly suited to widely spaced crops as papaya. Irrigation through the drip @ 6-8 lit/ day/ plant gives better yields. Drip irrigation helps to save 50%~60% water. Though multiple field trials have shown to economic beneficial use of drip irrigation in other crops, minimal information is available on the use of drip irrigation for papaya production (Kowalski and Zimmerman, 2001; 2006).
Results and Discussion
The time trend indicated a gradual increase in relative water content of leaf up to 7th MAP with a decline beyond this period. A gradual and significant reduction in water content of the leaves was observed due to reduction in evaporation replenishment at various levels at all the stages of growth. Here again, T1 maintained the highest water content of 87.7% at 7th MAP and T8 registered the lowest value of 69.4, which also showed about 20% reduction in water content of the leaves over T1. Jeyakumar et al (2007) also recorded a significant reduction in relative water content in grapevine under water deficit condition.). El-Tayeb (2000) explained that maintenance of high relative water content was the consequence of higher osmolyte concentration in drought tolerance cultivars of Vicia faba (Table 1).


Table 1 Effect of different levels of stage wise evaporation replenishment on leaf relative water content


The mean soluble protein content was ranging from 14.95 to 25.52 irrespective of the treatments and stages. At 5th MAP, T1 recorded a significantly higher value of 18.4 which was increased to the maximum level of 28.6 at 7th MAP. T2 closely followed T1 with the value of 27.3. All the other treatments showed a significant decline in the protein content due to reduction in percentage of evaporation replenishment. The lowest value of 22.9 was recorded by T8 at 7th MAP with a per cent reduction of 13.7 over T1. At final stage of growth also T8 registered the lowest level of 12.4 with the per cent reduction of 15 over T1. Kramer (1983) also reported that synthesis of protein was impaired in plants under water stress and in extreme stress conditions, protein degradation took place (Figure 1). The amino acid accumulation associated with water stress may actually be a part of an adaptive process contributing to osmotic adjustment as observed by (AliAhmad and Basha, 1998).


Figure
1 Effect of different levels of stage wise evaporation replenishment on soluble protein content


The stability index of chlorophyll was significantly influenced by all the treatments, at all the stages of growth.Initially, a mean CSI of 74% was recorded, which increased to 81.92% at 7th MAP. This again declined to 72.75% at final stage of observation. At 7th MAP the highest CSI of 85.74% was registered by T1 followed by T2 (84.52) and T3 (83.58). T8 recorded the lowest value of 78.16% at this stage, followed by T7 (78.61) which, in turn, resulted in 8.8% and 8.3% reduction respectively over T1. At final stage of growth also T1 showed its superiority in maintaining higher CSI of 76.15%.
Nagajothi (2005) in pigeon pea indicating 7.0% to 12.0% reduction in chlorophyll stability index under water deficit condition. Madhan Mohan et al (2000) reported that higher chlorophyll stability index helped the plants to withstand stress through better availability of chlorophyll, which resulted in increased photosynthetic rate, more dry matter production and higher productivity (Figure 2).


Figure 2 Effect of different levels of stage wise evaporation replenishment on chlorophyll stability index


Nitrate reductase activity was significantly influenced by various levels of evaporation replenishment at all the stages of growth. Initially, a mean value of 117.11
was recorded, which increased to 152.17 at 7th MAP and declined to 119.26 at the final stages of growth. At 7th MAP, which coincided with fruit development stage, T1 registered the highest value of 202.01. This treatment was followed by T2 (193.33) and T3 (182.4). T8 recorded the least value of 96.22 with a reduction of 21 per cent over T1 (Figure 3). The reduced nitrate reductase activity was due to decrease in nitrate content, caused by reduced nitrate uptake under water stress condition as observed by Yadav et al (1997) in chickpea. Hufaker et al (1970) revealed the sensitivity of NRase to even mild water stress ranging from -0.2 to -0.4 Mpa of leaf water potential.


Figure 3 Effect of different levels of stage wise evaporation replenishment on nitrate reductase activity


Materials and Methods
The experiment consists of eight treatments viz., 100: 100:100%ER (T1) 80:60:80%ER (T2) 80:60:60% ER (T3), 70:60:70%ER (T4). 70:60:60 %ER (T5), 60:60:60%ER (T6), 60:40:80%ER (T7), 60:40:60% ER (T8) at Transplanting to flower emergence and Flowering to first harvest and First harvest to end of first cropping period. The observations on physiological characters were recorded in monthly intervals starting from 4th month to 10th month after planting from each replication of the treatment.
Leaf samples from the middle of 5~6 cm of the youngest fully expanded leaves were collected and estimated as per the method of Weatherly (1950) and expressed as per cent.Soluble protein content was estimated from the leaf samples following the method of Lowry et al (1951) and expressed as mg/g fresh weight. The chlorophyll stability index was estimated by using the method of Murty and Majumdar (1962) and expressed in per cent.Nitrate reductase activity of the physiologically active leaves was determined by adopting the method of Nicholas et al(1976) and the enzyme activity was expressed as µg of NO2 g-1 fresh weight hr-1.The treatments were replicated thrice in Randomized block design.
Acknowledgement
First author is thankful to Tamil Nadu state council for science and technology for funding to carry out the study.
References
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