dwarfing in ornamentals
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Pratiksha Kumari 20306Division of Floriculture and Landscaping
(use of shrubs as potted plants)
IMPORTANCE OF DWARFING Control of plant growth imp in modern plant
production.
Short, homogenous plants, more robust
Easy to harvest, transport and sell.
Compact growth desirable, difficult to obtain by
traditional breeding.
Cereals, grasses, fruit trees and ornamentals, are
regularly treated chemically to control their stature
and flowering time.Indian Agricultural Research Institute, New Delhi
IMPORTANCE OF DWARFING FOR ORNAMENTAL SHRUBS
• Dwarf ornamental shrubs, used as permanent
landscaping, pot plants.
• Require little care compared to seasonal bedding
plants or large ornamental shrubs.
• Same foliage and flowers as large shrubs.
• Typically 1-3 feet tall, use lesser water and
fertilizer.
Indian Agricultural Research Institute, New Delhi
DWARFING TECHNIQUES:
Synthetic Growth regulators
Photopeiodic control
Thermoperiodic control
Water Stress
Breeding approaches
Indian Agricultural Research Institute, New Delhi
Indian Agricultural Research Institute, New Delhi
CASE STUDY-I
Effects of Water Stress and Selected Plant Growth Retardants on Growth
and Flowering of ‘Raspberry Ice’ Bougainvillea
(S. Ma and M. Gu )
Indian Agricultural Research Institute, New Delhi
Acta Horticulture ;2012. 937, 237-242.
Indian Agricultural Research Institute, New Delhi
Needs a lot of labor-intensive pruning (as potted plant).
PGRs alternatives to frequent prunning
Daminozide, paclobutrazol and chlormequat reported to be effective in controlling plant height.
to examine the effects of WS, daminozide and chlormequat on growth and flowering of ‘Raspberry Ice’ bougainvillea.
MATERIALS AND METHODS Plant Materials and Culture
195 12-cm tall ‘Raspberry Ice’
bougainvillea cuttings used
Every 3 cutting were potted up in 20 cm
pots
Plants irrigated as necessary with water-
soluble fertilizer 200 mg (20−4−6)
Prunned to 15cm in height .
Indian Agricultural Research Institute, New Delhi
Indian Agricultural Research Institute, New Delhi
• Plants treated with 2-week, 3-week and 4-week WS
• Tap water (150 ml) provided to each WS plant after that .
• Saucers placed under pots to ensure the 150 ml water was fully absorbed
Water Stress Application
PGR Application-Daminozide (1,250, 2,500, and 3,750 ppm)
Chlormequat (300, 600, 900 ppm)
Daminozide/chlormequat (800/1,000, 1,250/1,250,
and 2,500/ 1,500 ppm)
Foliar sprayed with a trigger sprayer at 20 mL PGR
solution/pot .
Control plants were not subject to PGR or WS
treatment.
Indian Agricultural Research Institute, New Delhi
RESULTS :Growth • Water stress showed significant impact on both plant height
and width
• PGR treatments did not
Flowering• All treatments show higher %age of flowering (33.3% to 60%).
• Daminozide as foliar spray, more flowers/pot than other
treatments .
Indian Agricultural Research Institute, New Delhi
Treatments Height (cm) Width (cm)
Control 30.8 84.9
WS 22.5 66.5
Daminozide 27.9 87.0
Chlormequat 33.0 87.0
Daminozide/Chlormequat
30.7 92.9
Table of WS and PGR applied to growth of “Raspberry Ice” Bougainvillea in 2009
WS (2 week, 3 week, 4 week water stress combined) Daminozide (1,250,2500, and 3750mg/L treatments combined)Chlormequat (300, 600, and 900 mg/L treatments combined)Daminozide/Chlormequat (800/1000,1250/1250,2500/1500 mg/L treatments combined)
CASE STUDY-II
Indian Agricultural Research Institute, New Delhi
Use of uniconazole to control height of Hibiscus rosa sinensis
(Steven E. Newman et.al)
HortScience; 1989 24(6):1041
Indian Agricultural Research Institute, New Delhi
Indian Agricultural Research Institute, New Delhi
For growing in pots and for
landscaping dwarf plants
preferred.
Chloromequat chloride
induce shortened internodes &
darken green leaves (Wilkins
and Kotecki, 1985).
Research evaluates the
effectiveness of Uniconazole
for control of plant height,
width, leaf distortion and no of
breaks/ plant
METHOD:Rooted cuttings of hibiscus rosa sinensis l. Cv ‘brilliant’ selected
Plants fertilized weekly with 200 mg n/ Litre (20N-8.6P-16.6K) at each
irrigation.
Plants pinched and flower buds were removed
Plants sprayed with uniconazole at 0, 10, 15, or 20 mg a.i./ Litre.
Ten plants treated at each of the given rates.
Indian Agricultural Research Institute, New Delhi
RECORDING OF OBSERVATIONS:
Data collected 77 days after treatments
were applied, when all hibiscus plants were in
full flower.
plant height (from the potting mediun
surface)
width (the average of two measurements
taken perpendicular to each other ),
stem length, leaf distortion, number of
breaks, and days to flower.Indian Agricultural Research Institute, New Delhi
RESULTS :Plant height
Height were reduced by all application rates of uniconazole,
with the main effect on height occurring at rates <15 mg./litre
0 5 10 15 200
1020304050607080
Uniconazole(mg a.i./litre)
Indian Agricultural Research Institute, New Delhi
Width plant width was reduced linearly for each unit increase in concentration
0 5 10 15 2005
1015202530354045
plant width(...
Indian Agricultural Research Institute, New Delhi
Leaf distortion significantly increased with increased application rates of uniconazole . where 1=no distortion to 10=severe
0 5 10 15 200123456789
10
leaf distortion
Uniconazole (mg a.i./liter)
Indian Agricultural Research Institute, New Delhi
Number of breaks It is increased with increased uniconazole application
0 5 10 15 200
5
10
15
20
25
no of bre...
Indian Agricultural Research Institute, New Delhi
INFERENCES :
Maximum reduction in plant height with Uniconazole
application at 15 mg/litre.
Leaf distortion maximum at 15 mg/L. plants treated with
10 mg/L were of high quality with minimal levels of
distortion and curling
15 - 20 mg/L severe distortion and of poor quality.
Uniconazole @ 10 mg a.i./L controlled height
promising method for height control and plant quality
improvement .
Indian Agricultural Research Institute, New Delhi
Indian Agricultural Research Institute, New Delhi
CASE STUDY-III
Application of growth regulators to Ornamental shrubs for use as
interior decoration( Joustra M. K. et.al)
Acta Horticulturae ;1989 251:359-369.
Indian Agricultural Research Institute, New Delhi
Screening of shrubs for indoor
performance have started
The need for regulation of
growth and / or flowering have
become evident.
Aspects of such experiments on
Clematis , Hydrangea
macrophylla, Rhododendron
(azalea) , Skimmia sps, Hibiscus
rosa sinensis, Choisya ternata,
Viburnum tinus, Vaccinium vitis,
briefly discussed here.
Indian Agricultural Research Institute, New Delhi
CLEMATIS
• Branching of clematis ‘Capitan Thuilleaux’ can be improved with dikegulac-Na and promalin (1:1 6-BAP+GA4+7)
• 14 mL promalin/L spray solution is sufficient to get good branching .• For compact growth of clematis cvs paclobutrazol gives good results .
HYDRANGEA MACROPHYLLA
• Plant height of hydrangea macrophylla Cv was effectively controlled by daminozide , ancymidol, or by paclobutrazol
• Not by chlormequat.• Gibberelin together with lightning speeded up flowering .• Only ancymidol and paclobutrazol stimulated inflorescence initiation of plants.
Indian Agricultural Research Institute, New Delhi
RHODODENDRON (AZALEAS )
• Retardation of growth by daminozide, chlormequat, or by paclobutrazol.• Branching induced by spray application of mefluidide.• Application of acifluorfen as a soil drench promote more shoot.
SKIMMIA SPECIES
• Skimmia plants perform very well indoor .• So studies have been conducted on the effect of GA and CT on growth and • branching of the second flush of this plant.
Indian Agricultural Research Institute, New Delhi
CHOISYA TERNATA
• Growth can be retarded by the use of paclobutrazol, but not with other GRs.• Since flowering than is also delayed with this application means other than
use of GRs have to be worked on.
VIBURNUM TINUS
• Heavy growth retardation was observed in treatment with paclobutrazol and high conc of daminozide or ethephon.
• Initiation of flowering during early stage of growth can also be achieved by the use of paclobutrazol
Indian Agricultural Research Institute, New Delhi
VACCINIUM VITIS
• Treating of plants with a combination of daminozide and ethephon ,together with a cold treatment just before forcing to flowering resulted in compact growth of the plants.
• This method offers good possiblity of using vaccinium as pot plant.
Indian Agricultural Research Institute, New Delhi
• Application of growth retardant chlormequat immediately after topping
• And a second spray when the plants reach 5cm height
HIBISCUS ROSA SINENSIS
Indian Agricultural Research Institute, New Delhi
•Use of growth regulators in dwarfing of ornamental shrubs for use
as pot plants can be undertaken.
•There are many side-effects associated with use of GRs, so before
their use proper study must be conducted.
•There are many GRs which along with suppressing growth also
promote the formation of flower buds.
•Study on interaction of climatic factors and GRs treatment still
needs attention.
•Breeding on dwarfing can also sometimes overcome the use of GRs.
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