PertanikaJ. Trop. Agric. Sci. 26(1): 59 - 64 (2003) ISSN: 1511-3701© Universiti Putra Malaysia Press

Potential of Paclobutrazol for Controlling Excessive Growth of Acaciamangium and Storing Recalcitrant Dipterocarp Seedlings for

Forest Rehabilitation

SHEIKH ALI ABOD & MUHAMAD BOKHARI FADZINFakulti Perhutanan

Universiti Putra Malaysia43400 UPM, Serdang, Selangor, Malaysia

Keywords: Paclobutrazol, gibberellins, Acacia mangium, dipterocarp seedlings, growth control, recovery

ABSTRAK

Anak benih Acacia mangium akan membesar berlebihan apabila jadual penanaman di ladang tidak dapatdiselaraskan dengan jadual pengeluaran anak benih. Biji benih dipterokarp sebaliknya tidak dapat hidup lamadan perlu disemai segera untuk menghasilkan anak benih. Oleh kerana kaedah biasa untuk rnenyimpan bijibenih didapati belum lagi berkesan untuk mengekalkan kebolehidupannya, kaedah menyimpan anak benihdalam keadaan terbantut dengan menggunakan paklobutrazol dan kemudiannya disembur dengan asidgibberellik untuk menggalakkan semula tumbesaran apabila perlu bagi penanaman di ladang adalah satupilihan yang menarik. Kertas kerja ini melaporkan keputusan beberapa kajian berkenaan penggunaanpaklobutrazol dan asid gibberellik kepada anak benih A. mangium, Shorea leprosula dan S. parvifolia.Keputusan-keputusan dibincangkan dengan mengambil kira implikasi-implikasi untuk kegunaan praktikal.

ABSTRACT

Acacia mangium seedlings often overgrow in size when the timing between plant production and [zeld plantingcannot be synchronized. Dipterocarp seeds, on the other hand, are short-lived and when available need to be sownimmediately for the production ofplanting stocks. Since conventional storage methods have not been proven to besuccessful in maintaining the viability of these seeds, storing their seedlings at a slow growth phase withpaclobutrazol and applying gibberellic acid to induce growth recovery when needed for .field planting is anattractive option. This paper reports the results of various experiments on the use ofpaclobutrazol and gibberellicacid for A. mangium, Shorea leprosula and S. parvifolia seedlings. The results are discussed withimplications for practical application.

INTRODUCTION

Forest rehabilitation can take the form of therestoration of vegetative cover which may bepurely an ecological exercise or reforesting anarea with timber trees of commercial value. Inthe former, the sites are often very denuded andAcacia mangium is the principal species used inMalaysia. On the other hand, the better sites asin logged over forests are often rehabilitated byenrichment planting with commercialdipterocarp species.

Acacia mangium is selected to rehabilitatetailing sites, ex-shifting cultivated areas and otherdenuded sites because of the species' ability tosurvive and grow remarkably fast even in very

poor soils. In the nursery, however, excessivegrowth of A. mangium is a liability if transplantingin the field is delayed. Overgrown seedlings aredifficult to transport and plant and have poorsurvival rates because of root coiling andunfavourable root to shoot ratio resulting indesiccation post-transplanting (Abod and Ahun1989).

Adequate and continuous supply ofdipterocarp seedlings are unpredictable becauseof the gregarious flowering pattern of the mothertrees and the recalcitrant nature of the seeds.Dipterocarp seeds are short-lived and whenavailable need to be sown immediately for theproduction of planting stocks. Storage of these

SHEIKH ALI ABOD & MUHAMAD BOKHARI FADZIN

seedlings at a slow growth phase is one option toprovide planting material on a continuous basisfor various planting programmes. Factors thatare of main concern for storage of seedlings arethe quality of such seedlings during storage andthe potential of the stored seedlings to resumerapid growth on return to normal growthcondition (Tsan et al. 1997).

Paclobutrazol, a gibberellin biosynthesisinhibitor, has been reported to be effective incontrolling the growth of a wide range ofangiosperms (Williams 1982; Quinlan andRichardson 1984; Abod and Webster 1991). Thispaper reports the results of some preliminarystudies on the potential of paclobutrazol forcontrolling excessive growth of A. mangium andfor storing recalcitrant dipterocarp seedlings forforest rehabilitation.

MATERIALS AND METHODS

This paper reviews materials and methods froma number of experiments. In all cases potted,uniform size seedlings, well supplied with waterand nutrients were used in experiments in agreen house at Universiti Putra Malaysia,Serdang, Selangor. The air temperature rangedfrom 22°C at night to 38°C in the day and therelative humidity from 60 to 90 % while lightintensity was above 50% of full sun.

Paclobutrazol (PP333) was supplied byImperial Chemical Industries (ICI) in aqueoussuspension at a concentration of 250 gil with anactive ingredient content of 22.0% w/w. Its tradename is Cultar and chemical formula (2RS,3RS) - 1-(4 chlorohenyl) -4, 4 dimethyl 1-2(lH-l, 2, 4, triazol-l-yl) pentan -3-01). Thechemical was diluted in distilled water to give arange of concentrations. A surfactant (Du PontAgricultural surfactant) also supplied by ICI wasadded at a concentration of 2.0 mL/l. Theaerial parts of plants were sprayed to runoffusing a hand-held pressure sprayer.

Effects of Methods of Application

Experiment 1 tested the effects of fiveconcentrations from 0 (control) to 12 gilpaclobutrazol and four methods of applicationon 10 week-old A. mangium seedlings as follows:S Soil drenching at week 0 (i.e. at the start

of the treatment)Fl Foliar spray at week 0 (potting soil

protected from chemical)

F2 : Foliar spray at weeks 0 and 6 (potting soilprotected from chemical)

S+F: Foliar spray at week 0 (potting soilexposed to chemical)

The surfaces of the pots in the Fl and F2treatments were covered with plastic sheets toshield the soil from the foliar sprays.

Effects of Concentration and Frequency

of Application

~xperirnent2 tested the effects of foliar spraying(I.e. potting soil exposed to chemical deposits)paclobutrazol at 8 concentrations and 2frequencies of spray on 10 week-old A. mangiumseedlings.

Effects of Paclobutrazol and Gibberellic Acid onShorea leprosula and S.parvifolia Seedlings

Two experiments labelled as experiments 3 and4 wer~ conducted on the dipterocarp species.Ex~er~ent3 tested the effects of foliar spraying2 SIzes I.e. 20 and 45 cm tall S.leprosula andS.parvifolia seedlings to a wide range ofpaclobutrazol concentrations from 0 to 12.0 gil.When the results (Table 2) showed that growthcontrol was more effective on smaller seedlingsand ~at low concentrations were adequate,Expenment 4 was set up.

Experiment 4 tested the effects of spraying10 cm tall S.leprosula and S.paruifolia seedlings toa range of low concentrations from 0 to 1000~g/l :paclobutrazol. The effects of foliar sprayWith different concentrations of gibberellic acid(GA3) were also tested to determine the effectson the recovery in height growth ofpaclobutrazol-treated plants.

RESULTS AND DISCUSSION

Effects of Methods Application

Soil drenching (S) or soil and foliar spray (S+F)gave similar and statistically significant reductions(P~0.05) in height increment compared to thefohar spray alone at either one (Fl) or two (2)frequencies (Table 1, Fig. la). It appeared thatthe chemical can be absorbed by both the shootsand roots. Richardson and Quinlan (1986)reported paclobutrazol to be translocated almostexclusively in the xylem acropetally to themetistematic regions. The binding nature of thechemical with the soil colloidal particles might

60 PERTANIKAJ. TRap. AGRIC. SCI. VOL. 26 NO.1, 2003

POTENTIAL OF PACLOBUTRAZOL FOR CONTROLLING EXCESSIVE GROWTH OF ACACIA MANGIUM

account for the greater persistence of its effectsobserved in this study. Conversely, paclobutrazolwhen sprayed onto the foliage alone (F1 andF2), merely accumulated in leaves and was nottranslocated into other shoot tissues; the quantityof chemical reaching the sites of action wasoften reduced. Foliar spraying of the shoot whichinevitably would also result in deposition of thechemical to the soil (if unprotected) appearedto be the most effective and pragmatic methodof application.

Effects of Concentration and Frequency of

Application

The results revealed the main effects ofconcentration (Table 1, Fig. 2) and frequency ofapplication (Table1, Fig.la) to be significant inreducing height increment. This concurs withthe works of Tsan (2000) on recalcitrantdipterocarp seedlings at the Forest ResearchInstitute of Malaysia.

The results in both experiments 1 and 2revealed that paclobutrazol-treated plants hadsignificantly lower height increments than thecontrol. The growth reduction increased withincreasing chemical concentration and time afterapplication (Table 1, Figs. 1b and 2)

Two frequencies of spray in bothexperiments 1 (Fig. la) and 2 (Table 1) gavestatistically greater reduction in height growth.Abod and Leong (1993) suggested that theuptake and translocation of the chemical at thesecond spray additively act together with theremaining triazole compounds from the previousapplication.

Minimal height increments were recordedfor treated plants from the onset of spray to 8weeks for both species (Figs. 3a, 3b). On theother hand, control plants grew markedly inheight recording up to 400 percent moreincrement at week 8.

At week 8, all paclobutrazol-treated plantswere sprayed with gibberellic acid (GA3) at 100,300 and 500 mg/l to induce a recovery in heightgrowth. The results in Fig. 3a and 3b revealedthat the recovery in height growth was instant inall treatments. Generally, the recovery was morepronounced in plants initially treated with a lowconcentration of paclobutrazol and subsequentlygiven a higher dosage of gibberellic acid. Atweek 16, eight weeks after the GA3 treatment,most of the paclobutrazol-treated plants recordedsignificantly greater increment than the controlfor both species.

TABLE 1Main effects of pac1obutrazol on the growth of A. mangium seedlings 12 weeks after treatment

Experiment 1 Experiment 2

Factor Height Factor Height incrementincrement (em)

(em)

Method of Soil 4.5 Concentration 0_ 10.7application Foliar F1 7.2 0.25 7.4

Foliar F2 6.1 0.5 5.1Soil & Foliar 4.4 1.0 2.5

2.0 2.58.0 2.312.0 1.2

F-test ** F-test **Sed 0.11 Sed 0.50

Concentration 0 13.3 Frequency 1 5.1(gil) 0.5 5.0 of spray 2 3.3

1.0 4.34.0 2.712.0 2.5

F-testSed

**, p<O.Ol; Sed in standard error difference

**0.12

F-testSed

**0.25

PERTANlKAJ. TROP. AGRIC. SCI. VOL. 26 NO.1, 2003 61

SHEIKH ALI ABOD & MUHAMAD BOKHARl FADZIN

LSOO.OS

o SOIL + Fl

5 6 7 10 11 12Weeks alter TreatmentJf F2 • SOIL & FOLIAR

LSD 0.05

Fig. 1a: Effect of method of applying paclobutrazol on the height incrementof Acacia mangium seedlings

14 .,----------------------------;

U

12

11

10

o 0

o

+ 500

2 5 6 7 IIWooks attor Troa1mont

Jf 1000 • 4000

to 11 12

)( 1200001g.ll

'2r10

! 8Cv.E 6~u.5.c 4co0c::;

::c 2

0

Fig. 1b: Effect of concentration of paclobutrazol on the height incrementof Acacia mangium seedlings

.Ogt-I

.... 2 gl-'* 0.25 gt·'o 4gl"

o 0.5gt-''" 8gt-'

(r 1 gt·'.12gt·'

62

Fig. 2: Main effect of concentration of paclobutrazol on the weekly heightincrement of Acacia mangium seedlings

PERTANlKAJ. TROP. AGRIC. SCI. VOL. 26 NO.1, 2003

POTENTIAL OF PACLOBUTRAZOL FOR CONTROLLING EXCESSIVE GROWTH OF ACACIA MANGlUM

TABLE 2Main effect of paclobutrazol on the growth of Shorea leprosula and S. pavifolia seedlings 12weeks after treatment for factor 1 (species), factor 2 (size) and factor 3 (concentration)

Factor Height increment (cm)

SpeciesS. leprosulaS. parvifolia

Df=1 SedF-test

4.94.3

0.02

**SizeBig (45 cm)Small (20 cm)

Df=1 SedF-test

6.52.8

0.02

**Concentration (gil)o0.10.250.51.02.04.08.012.0

Df=8 SedF-test

11.68.27.55.84.02.71.20.70.7

0.58

**** p<O.Ol; Sed is standard error difference

25 --------------..--_~ _ ._._---------_ _--------_ -.. _ _ _ -.

20

16151312117 6 g 10Weeks arler treatment

6532

.rg:dirllt:ir:n aE [ICld:x..~::Il.

......-CQ(\tTol --100A -"--1000 ~100c -....25OA --2508 -t-25OC SOOA

-6008 __ 600C ......-·75'JA 7508 --!of- 7SOC _--1000A ----10008 ---t--1000c

A= 100 mgll GA:!8= 300 mgJl GA:!C= 500 mgll GkJ

Fig. 3a: Effect of paclobutrazol and gibberellic acid on the height increment of Shorea pavifolia

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 26 NO.1, 2003 63

SHEIKH ALI ABOD & MUHAMAD BOKHARI FADZIN

Fig. 3b: Effect of paclobutrazol and gibberellic acid on the height increment of Shorea laprosula

CONCLUSION

Paclobutrazol is a cheap, effective and practicalmethod for controlling the growth of A. mangium,S.leprosula and S. parvifolia seedlings.

Storage of the dipterocarp seedlings at aslow growth phase inhibited by paclobutrazolmay be the solution to a regular supply ofplanting stocks. The ability of such seedlings torecover and gain rapid growth when treatedwith gibberellic acid gives further credence tothis method of storage.

Further research is necessary to developblueprints for practical application.

REFERENCES

ABOD, S. A. and]. ABUN. 1989. Root and shootgrowth and their manipulations of Acaciamangium seedlings. Mal. Far. 52(3): 136-145.

ABOD, S. A. and C. K LEONG. 1993. Effects of agrowth retardant and shoot pruning on thegrowth of Acacia mangium seedlings. J Trop.Far. Sc. 6(3): 239-48.

ABOD, S. A. and A. D. WEBSTER. 1991. Theinfluence of foliar sprays of tetcyclasis orpaclobutrazol on the growth and water useby transplanted Malus, Tilia and Betula stocks.J Hort. Sc. 66(1): 85-94.

QUINlAN,]. D. and P.]. RICHARDSON. 1984. Effectsof paclobutrazol on apple shoot growth.Acta Horticulturae 146: 105-111.

RICHARDSON, P.]. and]. D. QUINLAN. 1986. Uptakeand translocation of paclobutrazol by shootsof M.26 apple rootstocks. Plant GrowthRegulatar 4: 347-56.

TSAN, F. Y. 2000. Storage of seedlings of threerecalcitrant dipterocarp species by slowgrowth techniques. Ph.D. dissertation.Universiti Putra Malaysia. 358p.

TSAN, F. Y, J. BASHARUDDIN, K. AWANG andB. KRISHNAPILLAY. 1997. The growthperformance of the seedlings stored onthe forest floor. In Proc. of the FourthCon! on Forestry and Forestry ProductsResearch, October, FRIM, Kuala Lumpur.

WILLIAMS, M. W. 1982. Vegetative control ofapples with bioregulant ICI PP333. Hort.Sci.: 17-577.

(Received: 11 October 2001)(Accepted: 8 October 2002)

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