Abstract: A field investigation was conducted on cotton during 2002-2003 at Tamil Nadu Agricultural University, Coimbatore, India to study the influence of Atonik (nitro phenolic compound) on quality improvement in cotton var. MCU 12. The quality parameters viz., fibre length, uniformity ratio, fibre fineness, bundle strength and elongation ratio was significantly influenced by Atonik treatments. Among the stages of application, Atonik applied during square formation, flowering and boll set stages was found to be superior, followed by application during flowering and square formation stages. Among the concentrations used, application of Atonik at 0.25% was found to be highly effective in increasing all the quality attributes. Increased fibre length in Atonik treated plants (0.25%) may be attributed to the increased internal auxin pool or due to modulation in the turgor of cell wall altered by cell elasticity, as it is the mode of action of auxin.
INTRODUCTION
Indian cotton, as an industrial raw material for a flourishing textile industry is at the crossroads today. On the one hand, it has to relentlessly, face the onslaught from foreign cottons imported into the country that are contaminant-free, clean and of better quality. Cotton’s current share of the world textile market is now estimated to be 41.9% with current projection that cotton’s share will decline to 40% in 2005. This is mainly due to poor quality of fibres[1]. Hence, there is a need to improve the quality of cotton fibre. Quality in cotton can be improved by application of plant growth regulators. Foliar application of CCC improved the fibre quality in American cotton[2]. Malik et al.[3] reported that CCC reduced the cellulose synthesis and hence increased the rate of elongation thereby increasing the fibre length. Brassinolide application improved fibre quality characters like fibre length, uniformity ratio, fibre fineness and bundle strength in cotton[4]. Gialvalis and Seagull[5] reported that application of IAA or GA increased fibre production by increasing the proportion of epidermal cells that differentiated as fibres. Hence, an attempt was made to study the influence of Atonik on quality parameters viz., fibre length, uniformity ratio, fibre fineness, bundle strength and elongation ratio in cotton.
MATERIALS AND METHODS
Field experiment was conducted during 2002-2003, at Tamil Nadu Agricultural University, Coimbatore, India, under irrigated conditions to assess the quality effect of Atonik in cotton. The experimental design followed was factorial randomized block design with three replications by maintaining a plot size of 4x5 m.
Treatment consisted of two factors, stages of application and concentration. Stage was represented as S and concentration as T.
| T1 | - | Control |
| T2 | - | Seed treatment of Atonik 3 ppm |
| T3 | - | Foliar spray of Atonik 0.1% |
| T4 | - | Foliar spray of Atonik 0.25% |
| T5 | - | Foliar spray of Atonik 0.5% |
| T6 | - | Foliar spray of NAA 40 ppm |
| S1 | - | Foliar spray of Atonik at square formation stage |
| S2 | - | Foliar spray of Atonik at square formation and flowering stages |
| S3 | - | Foliar spray of Atonik at square formation, flowering and boll set stages |
Bolls were collected from all the concentrations of Atonik sprayed, NAA and control plots of cotton at harvest. Fibre quality characters were tested at the Department of Cotton, Tamil Nadu Agricultural University, Coimbatore. Fibre characters were determined from twenty random lint samples collected from each plot. All parameters were estimated in high volume instrument Uster model: HVI Classic 900. Ginning percentage was arrived by collecting one hundred seeds with fibre (kapas) from a plant and weighed. Then they were ginned by using a hand gin to separate the lint (fibre) from the seeds. Quantity of the lint obtained was weighed. The ratio of lint obtained from kapas taken was calculated and expressed as ginning out turn in percent[6].
Fibre length is the length of fibre representing majority of the fibres and expressed in mm[7]. Uniformity ratio of span length at 50% span over that at 2.5%. It was worked out as per the formula given below and expressed in percent.
Fibre fineness (micronaire value) is a relative measure of size, diameter and linear density of fibres and expressed in μg inch-1. Bundle strength denotes the fibre strength and otherwise known as tensile strength. It indicates the maximum specific stress that is developed in a tenacity test to rupture the fibre. IAA was estimated according to the methodology of Dunlap and Guinn[8] and expressed in ng g-1 DW. Statistical analysis was carried out as per Gomez and Gomez[9].
RESULTS
Fibre length (mm): The mean values of fibre length were found to vary significantly between treatments, stages and its interaction. Among the stages of application, S3 (application of Atonik at square formation, flowering and boll set stages) recorded a value of 32.17, which was 1.6% increase over S1. Among the treatments, maximum fibre length was observed in T4. The lowest fibre length was recorded by the treatment T2. In treatment combination, S3T5 proved to be the best by recording a value of 33.54, followed by S3T4 (32.94) (Table 1).
Uniformity ratio (%): The mean values of uniformity ratio were found to vary significantly between T, S and TxS.
| Table 1: | Effect of Atonik on quality parameters in cotton |
| * Interactions only in foliar treatments | |
The S2 and S1 recorded a value of 46.70 and 45.70, respectively (Table 1). In treatments, value of uniformity ratio varied between 45.10 (T2) to 46.87 (T4). The treatment T4 and T6 recorded the highest uniformity ratio and was followed by T5 (46.53). The best treatment (T4) recorded an increase of 3.8, 3.9 and 3.6% over control, seed treatment and Atonik 0.1%, respectively. In combination, S3T3, S3T4 and S3T5 were found to be on par with each other. S2T6 were found to be most superior.
Fibre fineness (μg inch-1): S3 (application of Atonik at square formation, flowering and boll set stages) recorded an increase of 3.0% over S1 (application of Atonik at square formation) (Table 1). The stage of application, treatments and their interaction were found to be significant. In treatments, fibre fineness ranged from 3.75 (T2) to 4.12 (T6). The best treatment, T6 recorded an increase of 8.4, 9.8 and 7.8%, over control (T1), seed treatment (T2) and Atonik 0.5% (T5), respectively. In the treatments combination, the highest fineness was observed in S3T3 (4.32), followed by S3T6 (4.22). S, T and SxT were found to be significant.
Bundle strength (g t-1): Bundle strength was more in S3 (25.56) followed by S2 (24.91) (Table 1). Among the treatments, T4 recorded a highest value (25.54) and T1 (23.77) recorded a lowest values. The treatment, T2, T3, T5 and T6 recorded a value of 24.57, 25.34, 25.44 and 25.28, respectively. Among the interaction, S3T4 was the best (26.21) and it was followed by S3T3 (25.91).
| Table 2: | Effect of Atonik on IAA content (ng g-1) at different growth stages in cotton |
| * Interaction only in foliar treatments | |
The treatment, stage of application and their interaction was found to be significant.
Elongation %: Application of Atonik at square formation, flowering and boll set stages increased the elongation percent (Table 1). The per cent increase over S1 and S2 was 6.0 and 3.9, respectively. Among the treatments, T4 recorded an elongation per cent of 5.32, whereas the control had an elongation per cent of 4.70. In combination, S3T5 recorded an elongation per cent of 5.52, which was followed by S2T4 (5.42) and S3T4 (5.32) and S3T6 (5.32). S, T and S x T were significant.
IAA content: IAA content showed an increasing trend over the period of growth, upto boll set stage (Table 2). Application of Atonik at square formation, flowering and boll set stage (S3) significantly increased the IAA content by 9.6 and 24.3% over S2 and S1 at boll set stage, respectively.
Comparing the concentrations of Atonik foliar spray, NAA foliar spray, Atonik seed treatment, Atonik 0.25% recorded a value of 1652.19 whereas T6 (NAA 40 ppm) had an IAA content of 1368.23, which is a 20.7% decrease over T4 at boll set stage. This treatment recorded an increase of 80.0 and 79.6% over control and seed treatment respectively at the above said stage. There exists a significant variation in IAA, due to Atonik spray, at all growth stages.
DISCUSSION
Cotton fibre develops as a single cell epidermal trichome on the seed coat. Cotton fibre length is commercially important parameters. Among the quality characters fibre length, bundle strength and elongation ratio were positively influenced by Atonik. Uniformity ratio and fibre fineness were enhanced by NAA application. Fibre length is one of the important criteria for spinning value and it determines the yarn strength and finest yarn size into which cotton can be spun[10]. As, Atonik treatment influenced these characters positively, it can be very well exploited in economic front. It is suggested that auxin (IAA) is the major hormone produced in response to fertilization and plays an important role in fibre production. Increased fibre length in Atonik treated plants (0.25%) may be attributed to the increased internal auxin pool. Cultivars that produce long staple have more auxin-like substances followed by middle and short staple cultivars[11]. Cotton fibre grows in four distinct phases of development viz., fibre initiation, elongation, secondary deposition and maturation, and dehydration[12]. Ultra structural evidences indicate that expansion occurs through a diffused growing mechanism, albeit with some bias for deposition of newly synthesized cell wall materials at the tip[13]. In Atonik treated plant, the more fibre length may be due to modulation in the turgor of cell wall altered by cell elasticity, as it is the mode of action of auxin. Fibre elongation per se involves the deposition of primary cell wall via secondary mechanism involving the dictyosomes and a protein synthesis mechanism ensuring sufficient supply of proteins required for the expansion of plasma membrane and tonoplast, while the rate of biosynthesis and degradation of IAA also dictates the rate of elongation[14].
Decreased IAA oxidase coupled with low polyphenol oxidase (data not shown) activity as observed in Atonik treated plants indirectly increased the internal auxin pool. At low IAA oxidase, profound effect of cellular level IAA would have effective role in cell wall extension and cell expansion. Prakash et al.[14] indicated that higher activity of this enzyme during the cell expansion has resulted in shorter fibre length. Further, as the secondary growth set in, the synthesis and availability of auxin became a limiting factor for fibre elongation. Increase in IAA content may positively influence the fibre development[14]. Thus, external application of Atonik might have resulted in accumulation of the IAA in ovule leading to higher numbers of fibres produced in the early stage of initiation. Increased fibre length in Atonik treated plant may be due to rapid water uptake, which might have facilitated the cell elongation. This is in accordance with the finding of Gokani and Thaker[15].