effect of plant growth regulators on morpho-physiological, biophysical and anatomical characters in

120 Pages·2009·1.74 MB·English

EFFECT OF PLANT GROWTH REGULATORS ON
MORPHO-PHYSIOLOGICAL, BIOPHYSICAL AND
ANATOMICAL CHARACTERS IN COTTON

Thesis submitted to the
University of Agricultural Sciences, Dharwad
in partial fulfillment of the requirements for the
Degree of

DOCTOR OF PHILOSOPHY
in
CROP PHYSIOLOGY

By
PRAKASH KOLER

DEPARTMENT OF CROP PHYSIOLOGY
COLLEGE OF AGRICULTURE, DHARWAD
UNIVERSITY OF AGRICULTURAL SCIENCES,
DHARWAD – 580 005

SEPTEMBER, 2008
ADVISORY COMMITTEE

DHARWAD (B.C.PATIL)
SEPTEMBER,2008 (CHAIRMAN)

Approved by :
Chairman :__________________________

(B. C. PATIL)

Members : 1. ______________________
(M. B. CHETTI)

2._______________________
(A. S. NALINI PRABHAKAR)

3._______________________
(I. S. KATAGERI)

4._______________________
(S. M. HIREMATH)
CONTENTS

Sl. No. Chapter Particulars Page No.
I. INTRODUCTION
II. REVIEW OF LITERATURE
III. MATERIAL AND METHODS
IV. EXPERIMENTAL RESULTS
V SUMMARY
VI. DISCUSSION
VII. REFERENCES
LIST OF TABLES

Table
Title
No.
1. Physical and chemical properties of the soil of experimental field
2. Weather data of Agricultural Research Station, Dharwad Farm for the
year 2005-06; 2006-07 and the average of past 25 years
3. Treatment details of the experiment
4. Effect of plant growth regulators on plant height (cm) at different growth
stages in cotton
5. Effect of plant growth regulators on number of leaves per plant at
different growth stages in cotton
6. Effect of plant growth regulators on leaf length (cm) and leaf width (cm)
at different growth stages in cotton
7. Effect of plant growth regulators on number of monpodia, sympodia,
nodes and internodal length in cotton
7a. Effect of plant growth regulators on number of fruiting bodies at
different growth stages in cotton
8. Effect of plant growth regulators on phenological characters in cotton
9. Effect of plant growth regulators on leaf dry weight (g plant-1) at
different growth stages in cotton
10. Effect of plant growth regulators on stem dry weight (g plant-1) at
different growth stages in cotton
11. Effect of plant growth regulators on dry weight of reproductive parts (g
plant-1) at different growth stages in cotton
12. Effect of plant growth regulators on total dry weight (g plant-1) at
different growth stages in cotton
13. Effect of plant growth regulators on absolute growth rate (g day-1) at
different growth stages in cotton
14. Effect of plant growth regulators on crop growth rate (g m2day-1) at
different growth stages in cotton
15. Effect of plant growth regulators on relative growth rate (g g-1 day-1) at
different growth stages in cotton

Contd…..
Table
Title
No.
16. Effect of plant growth regulators on net assimilation rate (g-1 dm-2 day-1)
at different growth stages in cotton
17. Effect of plant growth regulators on leaf area (dm2 plant-1) at different
growth stages in cotton
18. Effect of plant growth regulators on leaf area index at different growth
stages in cotton
19. Effect of plant growth regulators on leaf area duration (days) at
different growth stages in cotton
20. Effect of plant growth regulators on specific leaf weight (mg dm-2) at
different growth stages in cotton
21. Effect of plant growth regulators on chlorophyll ‘a’ content (mg g-1 fresh
weight) at different growth stages in cotton
22. Effect of plant growth regulators on chlorophyll ‘b’ content (mg g-1 fresh
weight) at different growth stages in cotton
23. Effect of plant growth regulators on total chlorophyll content (mg g-1
fresh weight) at different growth stages in cotton
24. Effect of plant growth regulators on nitrate reductase activity (µg NO g-
2
1 fresh weight) at different growth stages in cotton
25. Effect of plant growth regulators on membrane integrity (dS/m) at
different growth stages in cotton
26. Effect of plant growth regulators on yield and yield components in
cotton
27. Effect of plant growth regulators on fibre quality parameters in hybrid
cotton
28. Correlation co-efficient values of yield with growth and yield
components in cotton hybirds as influeced by PGRS (Pooled)
29. Effect of PGRS’s and spacing on yield and yield components, LAI,
TDM and biophysical characters in hybrid cotton (RAHB-87)
30. Effect of growth regulators on economics of interspecific cotton hybrid
(DHB-290)
LIST OF FIGURES

Figure
Title
No.
1. Weather data of ARS, Dharwad Farm, Dharwad (Karnataka)
2. Plan of layout of the experiment
3. Effect of foliar spray of PGRs on number of fruiting bodies in
cotton hybrids
4. Effect of plant growth regulators on plant height (cm) at different
growth stages in cotton
5. Effect of plant growth regulators on number of sympodia and
number of nodes in cotton
6. Effect of plant growth regulators on total dry weight (g/plant) at
different growth stages in cotton
7. Effect of plant growth regulators on leaf area index at different
growth stages in cotton
8. Effect of plant growth regulators on leaf area duration (days) at
different growth stages in cotton
9. Effect of plant growth regulators on specific leaf weight
(mg/dm ) at different growth stages in cotton
2
10. Effect of plant growth regulators on total chlorophyll content
(mg/g fresh weight) at different growth stages in cotton
11. Effect of plant growth regulators on nitrate reductase activity (µg
NO /g fresh weight) at different growth stages in cotton
2
12. Effect of plant growth regulators on yield and yield components
in cotton
13. Effect of plant growth regulators on fibre quality parameters in
hybrid cotton
LIST OF PLATES

Plate
Title
No.
1. Morphological view of growth regulators treated plants
2. Morphological view of comparison of growth retardants sprayed at
one stage (90 DAS) and at two stages (70 + 90 DAS)
3. Morphological view of comparison of growth promoters and
growth retardants treated plants
4. Morphological view of leaves treated with plant growth regulators
5. Anatomical view (40x) of plant growth regulator treated leaves
6. Anatomical view (10x) of plant growth regulator treated leaves
I. INTRODUCTION
Cotton is one of the most important fibre crops playing a key role in the economic and
social affairs of the world providing basic input to the textile industry. It is the oldest among
the commercial crops of the world and is regarded as white gold. Cotton is grown chiefly for
its fibre used in the manufacturing of cloth. Presently, India is the second largest producer of
cotton in the world having the largest acreage. In India, cotton occupies five per cent of the
total cultivated area, which is ¼th of the world’s area under this crop.
Cotton is grown in India from 80 - 32.50 latitude and 700 - 800E longitude with an
elevation ranging from 0 - 950 m. It is cultivated in areas where the average annual rainfall
ranges from 250 - 1500 mm and widely varying soil conditions in terms of colour, texture,
depth and nutrient status.
In India, cotton is cultivated in an area of 9.53 million hectares with a production of
31.0 million bales of seed cotton (170 kg/bale) during 2007 - 08 (Anon, 2008). The average
productivity of cotton in India is 599 kg lint per hectare, which is low when compared to world
average (733 kg lint/ha). In Karnataka, the area under cotton during 2000 AD was over 6.0
lakh ha with average productivity of 220 kg per ha, which is again low compared to Indian
average. Severe pest incidence, delayed sowing due to late release of water in the command
areas, increased cost of cultivation, unpredictable yields, lower returns on high investments,
etc. are the major reasons of lower productivity.
Cotton productivity in India is low due to the fact that more than 65 per cent of the
cotton area is under rainfed condition, low fertilizer consumption and low fertilizer user
efficiency. In addition, India has about 28 per cent of area under desi cotton (G. herbaceum
and G. arboreum) which are intrinsically low yielders due to the genetic and physiological
constraints like long duration, shedding of plant parts, leaf reddening, bad opening of bolls
and are grown in areas of high biotic and abiotic stresses. Cotton under the conditions of high
rainfall or irrigation produces excessive vegetative growth resulting in mutual shading and
shedding of reproductive parts, thereby reducing the yield. The desire to optimize plant
growth, while maximizing yield led to the use of interest in PGRs. In the past two decades
many new plant growth regulators have been developed and tested under field conditions.
Cotton is a sub tropical, perennial plant with indeterminate growth habit. Vegetative
and reproductive growth occurs simultaneously where vegetative growth is necessary to
support reproductive growth. The growth habits of these varieties/hybrids combined with high
availability of nutrients, timely rainfall or irrigation and delayed fruit retention can encourage
excessive vegetative growth. Excessive vegetative growth leads to severe production
problems like fruit abortion, delayed maturity, boll rot and harvest difficulties.
The physiological efficiency of a plant can be improved by prolonging photosynthesis,
reducing photorespiration, better partitioning of photo assimilates, improving mineral ions
uptake and stimulating nitrogen metabolism. All these processes are inter-linked through
several interactions and influence growth and productivity. Plant growth regulators have been
found to influence these processes in one way or the other.
Plant growth regulators are substances when added in small amounts modify the
growth of plant usually by stimulating or inhibiting part of the natural growth regulation. They
are considered as new generation of agrochemicals after fertilizers, pesticides and herbicides.
Plant growth regulators are capable of increasing yield by 100-200 per cent under laboratory
conditions, 10 - 15 per cent in the field conditions (Kiran Kumar, 2001). Plant growth
regulators like promoters, inhibitors or retardants play a key role in internal control mechanism
of plant growth by interacting with key metabolic processes such as nucleic acid and protein
synthesis. The most commonly used growth regulator in cotton is mepiquat chloride, which is
an inhibitor of gibberlic acid. This curtails excessive vegetative growth and increases the
yield.
Plant growth regulators are shown to change leaf resistance by altering stomatal
aperture, the rate of photosynthesis could be manipulated through this technology. IAA, GA,
kinetin, phenolics and aliphatic alcohols are reported to increase and stimulate the rate of
photosynthesis. In several species, the application of growth retardants is shown to stimulate
photosynthesis by increasing LAI, delaying leaf senescence, increasing the functional
duration of the leaf or delaying degradation of chlorophyll which has improved source-sink
relationship.
Cotton plant has a natural mechanism to prevent excessive vegetative growth with
higher nitrogen levels, soil moisture, temperature and fruit loss by insect, disease and
nematodes. In many cases, these factors are not well balanced and growth regulators are
needed to maintain proper plant size and to synchronize boll set and to regulate maturity.
Additionally, indeterminate varieties also require plant growth regulators to shift cotton from
vegetative to reproductive growth.
Mepiquat chloride is an anti-gibberelin that inhibits cell expansion but not cell division.
Its spray directs carbohydrates into reproductive organs and hence used to control plant
growth. It is available in different trade names that include pix, mepex, pixplus, pix ultra and
others. Pix, which is a growth retardant when applied as foliar spray reduces the vegetative
growth, leaves become coarse and dark green in colour (Cothren and Osterhuis, 1993; Brigg,
1980; York, 1983 and Edmisten, 2000).
With the above background, the present investigation was carried out with the
following objectives.
1. To know the effect of plant growth regulators on leaf anatomy and morphological
characters of cotton.
2. To know the effect of plant growth regulators on biophysical and phenological characters
of cotton.
3. To know the effect of plant growth regulators on membrane integrity and nitrate reductase
activity of cotton.
4. To know the effect of plant growth regulators on yield and yield components of cotton.
II. REVIEW OF LITERATURE
The role of plant growth regulators (PGR’s) on various physiological and bio-chemical
processes of plants is well known, which enables a rapid change in the phenotype of the plant
with one season to achieve desirable results. Plant growth regulators are known to affect right
from seed germination to senescence by enhancing the growth (growth promoters) reducing
the plant height (growth retardants), altered flowering, fruit set, seed development, fruit
ripening and yield. Cotton often produces more vegetative growth than is needed for
maximum boll production and yield especially when climatic conditions favour vegetative
growth, thereby directing the photo-assimilates towards the vegetative growth rather than
reproductive growth. However, in the recent past, different workers have emphasized the use
of various growth regulating chemicals for the control of vegetative growth in cotton. This
chapter emphasizes the recent work on plant growth regulators in cotton and their effect on
morphological, physiological, bio-chemical parameters and yield attributes.
2.1 EFFECT OF PGR’s ON MORPHOLOGICAL CHARACTERS
2.1.1 Plant height
Plant height and number of branches are influenced by interaction between the
environmental conditions and genetic make up of the plant.
Dastur and Prakash (1954) observed that foliar application of NAA @ 40 ppm
increased the plant height. Thomas (1964) reported that plants characteristically produce dark
foliage and develop short stem internodes, hence the term dwarfing chemicals to this class of
growth retardants. Later, they observed reduction in elongation of main stem, fruiting
branches and flowering. Annapan and Aaron (1969) reported that NAA increased the plant
height when sprayed at 60 and 75 DAS in cotton. Chokhey Singh et al. (1970) indicated an
increase in plant height by increase in sympodial branches and number of bolls per plant.
Plant height had strong correlation with number of branches and days to first flower.
Zur et al. (1970) found that application of CCC @ 50 and 100 g ai ha-1 at square
initiation stage reduced the plant height significantly. Application of CCC at 0.2 kg ha-1 before
flowering provided temporary check on the vegetative growth and reduced plant height (Singh
and Singh, 1970).
Gidnavar (1979) found that the application of CCC decreased the height of cotton
plant. Misra and Malik (1980) observed a reduction in height of plant with increasing
concentration of CCC. Walter et al. (1980) reported that the application of dimethyl
piperidinium chloride (DPC) @ 1500 ppm at first bloom stage in cotton reduced the plant
height by 28 per cent. Mulder et al. (1981) reported that spraying of mepiquat chloride at an
early reproductive stage in cotton reduced the plant height. Varela and Yellejo (1982)
reported that the application of DPC (25, 50, 70 g/ha) twice at 60 days after sowing and 15
days later resulted in the reduction of plant height in cotton. Virk et al. (1984) reported that
increased cycocel concentration reduced plant height in cotton.
Azab et al. (1987) reported that the application of cycocel at square initiation or at
flowering stage reduced the plant height in cotton. Sheshadri (1989) concluded that the
application of CCC to cotton decreased average plant height and internodal length. Kapagate
et al. (1989) reported that GA (500 ppm) was most effective in increasing plant height
followed by NAA (1000 ppm) in cotton cv. Branil 1007. Vyakaranahal et al. (1989) reported
that the influence of fertilizer dosage and five sprays (at 90,100,110, 120 and 130 days after
of sowing) of NAA (10 ppm) to female parent of Varalaxmi cotton hybrid helped to restructure
the plant by decreasing vertical growth and enhancing the lateral growth with significant
increase in monopodial and sympodial branches.
Ansari et al. (1989) reported that yield per plant correlated with plant height and boll
number, but not with number of monopodial branches. James (1991) reported that pix
reduced plant size and enhanced earliness. Pix partially inhibits one of the enzymes that is
involved in GA biosynthesis, produce fewer fruiting branches, shorter plant, shorter internodes
and higher per cent of fruit set by the application of pix (453.6 g ha-1) at early blooming stage
(Charles Stichler, 1991). Boquet and Coco (1993) opined that MC can be used to manage the
vegetative development of cotton plants to offset the effect of excessive irrigation or N
2