Temprate Fruits (1+1)

EXERCISE 14

EXERCISE 14: Preparation and uses of plant growth regulators in temperate fruits

Calculating the strength of growth regulators:
Strength of growth regulators is calculated in ppm (part per million). ppm is the mg of chemical dissolved in one liter of water e.g. 5 ppm means 5 mg salt dissolved in one liter of solvent. Following table will tell the interconversion of hormonal strength:

Per cent solution (%)	Miligram/litre (mg/l)	Parts per million (ppm)	Grams/litre (g/l)
100	1,000,000	1,000,000	1000
10	100,000	100,000	100
1	10,000	10,000	10
0.1	1,000	1,000	1
0.01	100	100	0.1
0.001	10	10	0.01
0.0001	1	1	0.001

Percentage =	ppm
	10,000
or ppm = %age x 10000
or ppm = % x 104

Preparation of growth regulator solution

• Weigh the required quantity of growth regulator. The quantity of chemical required will depend on volume and strength of the solution to be prepared and the purity of chemical used. In case the chemical is liquid, measure the required quantity wit the help of a pipette or syringe.
• It is always desirable to prepare the solution of higher strength as the lower concentration can be prepared easily by dilution.
• After weighing the chemical transfer it to a beaker and dissolve it with the suitable solvent.
• Shake the beaker till the chemical is fully dissolved. Now transfer it into volumetric flask and at necessary quantity of distilled water. For every use prepare a fresh solution.

The common uses of PGRs in fruit crops are as under:

Propagation : PGRs are being used commercially for rooting of cuttings, layering and seed germination.

Rooting of cuttings:

• The prepared cuttings should be treated with the growth regulator solution as soon as possible.
• Put the growth regulator solution in the beakers. Label the beakers properly with glass marking pencil.
• Make bundles of 10 or more cuttings for each concentration of individual growth regulator solution. Put the basal ends of cuttings in the solution.
• At least 2-3 cms of cuttings must be dipped inside the solution. Leave the cuttings in the solution to the desired time. In one beaker take distilled water and keep same number of cuttings for same duration of time as allowed in growth regulator solution.
• After the specific duration remove the cuttings from the solution and wash them with plain water and plant them in the medium already prepared. Commonly used hormones for rooting are as:

Sr. No.	Name of growth regulator	Suggested concentration (ppm)		Remarks
		Quick dip	Prolonged dip
1	Indole acetic acid (IAA)	500-1500	100-500	Roots produce are thicker and shorter
2	Indole butyric acid (IBA)	500-1500	100-500	More fibrous roots are produce hormones not toxic even at higher concentrations. Move slowly within the plant and destroyed slowly by auxin destroying enzymes. Excellent rooting hormones
3	Naphthalene acetic acid (NAA)	500-1500	100-500	This hormone is toxic if used at higher concentration

b)Treating cuttings with growth regulator powder :

• Take distilled water in a beaker. Dip the basal end of the cuttings in water.
• Only one to two centimeter basal end of the cuttings should be moistened.
• Dip the moistened end of cuttings directly in the growth regulator powder and immediately planted in rooting media in usual manner.
• Treating cuttings in talc powder is not satisfactory because the growth regulators is not evenly distributed in the talc powder.

Use of growth regulators in layering:

• First weigh the watch glass. Then put lanolin paste on the watch glass with the help of a glass rod.
• Weigh it again to get the weight of the lanolin paste.
• Weigh the growth regulator and dissolve it in suitable solvent. Heat the watch glass by putting it on a low flame.
• As paste melts add the growth regulator solution.
• Mix the solution with glass rod till homogenous mixture is formed. Remove it from the flame and let it cool.
• Prepare the air layer and apply the paste with the help of a glass rod on the upper side ringed area. The following growth regulators and their mixtures have been found to be effective on large number of plants in inducing rootings in layering:

Sr. No.	Name of growth regulator	Suggested concentrations (ppm)
1	Naphthalene acetic acid (NAA)	1000-10000
2	Indole butyric acid (IBA)	1000-10000
3	Indole acetic acid (IAA)	1000-10000
4	2,4 Dichlorophenoxy acetic acid (2,4-D)	250-500
5	NAA+2,4-D	5000+250
6	IBA + 2,4-D	5000+250

Germination :

• GA3 200 ppm has been successfully used for enhancing seed germination in apple, pear and stone fruits..

Fruit set :

• In apple, spray of miraculan 0.75 ml/l and paras 0.6 ml/l or biozyme or protozyme 2 ml/l at bud swell stage and repeated after petal fall stage improve fruit set and yield.

Fruit drop :

• In apple and pear spray of 10 ppm NAA about a week before expected fruit drop prevent fruit drop.

Fruit Thinning

• It has been observed heavy bearing in apple, pear and stone fruits during !on year!, results in small sized poor quality fruits.
• Therefore, judicious thinning at proper stage of fruit development is must to regulate cropping and improving fruit size and quality.
• The thinning can be achieved either by manually or with the use of growth regulators.
• Foliar sprays of 20 ppm NAA at petal fall results in optimum fruit thinning In peaches application of Ethephone (2-Chloromethyi Phosphonic Acid i,e. CEPA) 300 ppm at petal fall in July Elberta is recommended for optimum fruit thinning.
• However, in Red haven peach, Ethaphone (600ppm) 20-30 days after fruit set when the fruit lets are 20-25 cm in diameter, should be used for thinning.

Improvement of fruit colour and enhancement of maturity:

• In apple spray of 1200 ppm ethephone about a week before expected harvest improve fruit colour in mid hills and enhance fruit maturity in high hills. 25 ppm NAA should also be mixed with ethereal to prevent excessive fruit drop caused by ethereal.
• In plum spray of 500 ppm etheral about a week before harvest improve fruit colour. In apricot and peaches 2,4,5-T, 2,4-D, NAA or TIBA enhances fruit ripening and improve fruit colour and flavour.

Dormancy :

• Benzyl adenine (BA) 500 ppm and gibberellins 50 –200 ppm are effective regulators in breaking dormancy.
• Other chemicals used to break dormancy in fruit crops are Dinitro-ortho-cresol DNOC 1.5% as dormant spray,
• KNO3 2-5% helps in promoting more flower bud opening,
• Thiourea 2% promote more leaf bud opening and GA3 most effective in breaking dormancy in cherry and peaches.