Pertanika 13(2), 145-150 (1990)

Effects of Nutrient Deficiencies on the Root Regenerating Potentialand Growth of Pinus caribaea and Pinus kesiya Seedlings

SHEIKH ALI ABOD

Department ofForest ProductionFaculty ofForestry

Universiti Pertanian Malaysia43400 UPM, Serdang, Selangor Darul Ehsan, Malaysia

Key words: nutrient deficiencies, Pinus caribaea, Pinus kesiya, root regenerating potential.

ABSTRAK

Kejayaan penubuhan ladang bergantung kepada pengeluaran anak-anak benih yang berpotensi tinggi untukpertumbuhan akar baru dan ditanam di kawasan yang subur bagi menggalakkan tumbesaran akaritu. Banyakfakta di tapak semaian dan ladang mempengaruhi potensi pertumbuhan akar (PPA). Penyelidikan iniditumpukan kepada kesan kekurangan dua zat galian penting yang diperlukan oleh tumbuhan-tumbuhan,nitrogen (N) dan/atau fosforus (P) yang selalunya berkurangan di tanah tropika, pada PPA dan tumbesarananak benihPinus caribaea danPinus kesiya. Anak benihP. caribaea danP. kesiya yangmendapatizatgaliandengan cukup tidak terbantut daripada mengeluarkan akar baru selepas dipangkas akar dan dipindahkan kekawasan yangkurang zat galian (-N, -P& - NP). Selepas pemindahan, pokok yang mendapati semua zat galian(F) dan yang kurang P menunjukkan ketinggian dan perepang batang yang lebih berbanding dengan yangkurang N dan NP. Hasil kajian juga menunjukkan bahawa P. kesiya mempunyai PPA yang lebih tinggidaripada P. caribaea walaupun spesies pertama itu lebih rendah ketinggiannya pada permulaan eksperimen.Implikasi praktik hasil penyelidikan kepada amalan di tapak semaian dan penubuhan pokok di ladangdibincangkan.

ABSTRACT

Successful plantation establishment requires the production of seedlings with high root regenerating potential(RRP) to beplanted in an enviroment whichfacilitates theproduction ofnew roots. Numerousfactors in the nurseryand in thefield influence RRP. This study examines the effects ofa deficiency oftwo important essential elements,nitrogen and/orphosphorus commonly deficient in tropical soils, on the RRP and growth ofPinus caribaea andPinus kesiya seedlings. Given an adequate supply ofnutrients before transplanting in nutrient deficient sites, P.caribaea and P. kesiya showed a high capacity to regenerate root following root pruning and replanting intoconditions oflimited nutrient supply (-N, -P& -NP). Seedlings grown inF (full nutrients) and -P conditions weretaller and had thicker stem diameter than in -N or -NP. The results also show that P. kesiya had a higher RRPthan P. caribaea despite the shorter mean height ofthe former species at the start ofthe experiment. The practicalimplication of the results to nursery cultural practices and tree establishment is discussed.

INTRODUCTION

The problems of poor growth due to low soilfertility are more frequent and serious in theestablishment of plantation forests thenagricultural crops because the lands relegatedto forestry are often too infertile for

agricultural use (Abod 1980). Such problemsare more common in the tropics where soilsare generally deficient in many essentialnutrients (Thompson and Troeh 1973)particularly nitrogen (N) and phosphorus (P)(Gourou 1966; Kalpage 1974) necessary forhealthy vigorous growth of trees.

SHEIKH ALI ABOD

Pinus caribaea Mor. var. hondurensis B & Gand Pinus kesiya Royle ex Gordon are twospecies with considerable potential for plantingin tropical and subtropical areas (Lamb. 1973;Abod 1980) but much of the technology beingapplied in their establisment is adapted froma knowledge of species of more temperateorigin. A better understanding of their growthpattern and requirements are required inorder to develop optimum cultural practicesfor plantation establisment in the tropics.

A number of workers (Stone and Schubert1959; Abod et at. 1979; Abod and Wesbter1989; 1990) have stressed that the initialsurvival of planted seedlings depends chieflyon the ability of their root system to regeneratein the first few weeks after outplanting to re­establish contact with the surrounding soilmass and begin taking up water and nutrients.The work described here examines the effectsof deficiency in N, P, or both on growth, withparticular emphasis on the root growthcapacity of seedlings of P. caribaea and P. kesiya.It could have a useful practical application toknow whether any deficieny in these nutrientelements could significantly affect these speciesto regenerate roots vital for successfulestablishment in the first critical month afteroutplanting.

MATERIALS AND METHODS

Pinus kesiya, a montane species, and Pinuscaribaea variety hondurensis, a lowland specieswere used. P. kesiya seeds collected nearAgapang, Luzon, Philippines (lat. 17°33' N.,long 120°57' E., elev. 1300 m) were obtainedfrom the Division of Forest Research, CSIRO,Canberra. P. caribaea seeds were collected bythe Queensland Department of Forestry froma plantation at Maryvale, Queensland, whichhad been planted originally with seed from thelowland coastal plain of Belize.

Seeds were germinated and grown indi­vidually in plastic pots (15 cm diam.) con­taining 1:1 vermiculite-perlite mix, which waskept well supplied with water and nutrients.The seedlings were free of any associatedmycorrhizal fungi. Plants were grown in LBgrowth cabinet (Pescod et at. 1963) with aday/night temperature of 27/22°C which was

synchronized with a day length of 12 hoursthroughout the experiment.

Temperatures in the LB growth cabinetcould be controlled precisely within the range0-35°C programmed for separate day and nighttemperatures. Relative humidity was not con­trolled but was recorded to be above 50%throughout the duration of the experiment.Twenty-eight fluorescent and four incandescentlamps provided a light intensity of 80 watts permetre square at plant height. The lamps wereconnected to a time switch for photoperiodiccontrol.

At the commencement of the experiment,uniform sized seedlings 14-week-old andaveraging 12.0 cm tall and 0.26 cm root collardiameter for P. caribaea and 10.0 cm tall and0.26 cm root collar diameter for P. kesiya wereselected. Seedling variations were less then 0.5cm tall and 0.02 cm thick for either species.Preliminary trials had confirmed this to beessential to reduce to acceptable limits, thegreat variability of the results for rootregeneration. Similar problems with variabilityin root regeneration were noted by Stone etal. (1962). Space limitations allowed only eightreplicates to be used i.e. 2 species x 4 nutrienttreatments x 8 replicates.

Roots of all seedlings were pruned to astandard length and all white root tips pinchedoff to simplify recognition of new roots. Theplants were grown for 4 weeks in full nutrient(F), minus nitrogen (-N) , minus phosphorus(-P) , and minus Nand P (-NP). Plants weregiven these nutrients in the morning anddistilled water in the afternoon. Mter 4 weeks,they were harvested for measurements ofheight and diameter increment, root rege­neration, and root and shoot oven dry weight.Any morphological differences in the shootsbetween treatmens were compared.

The technique of Stone and colleagues(see review by Stone 1967) was used to assessthe root regenerating potential of the plants.All white root tips greater than 1 cm long werecounted and those greater than 2 cm weremeasured. Root regenerating potential isdetermined from both the total number (N)and length (L) of new roots per plant.

All data were subjected to analysis of

146 PERTANIKA VOL. 13 NO.2. 1990

EFFECTS OF 1 UTRIENT DEFICIENCIES 0 RRP AND GROWTH OF P. CARlBAEA AND P. KESfYA SEEDLI GS

variance and the significance of differencesbetween group means was tested with Duncan'snew multiple range test (Steel and Torrie 1960;Winer 1971).

RESULTS

The results of analysis of variance are given inTable 1 for the parameters measured in theexperiment. These was no interaction betweennutrients and species indicating a similarresponse to nutrient treatment in both species.

No colour difference was observed in thefoliage between different treatments for eachspecies at harvest.

Root regenerationRoot regenerating potential (RRP) based onboth number and length of new roots showedno significant difference between treatmentmeans for nutrient treatments. However, therewas a highly significant species difference(Table 1) due to P. kesiya producing more andlonger new roots in each treatment (Table 2).

Dry weightThere were no significant difference in totalroot and total plant dry weights between the

nutrient treatments or between speciesalthough there were differences in shoot dryweight for both factors (Table 1).

Table 2 shows that shoot dry weight in -Ptreatment was significantly greater than -NP butwas not significantly different from F and -N.As the -NP treatment did not differ significantlyfrom full nutrient this results is difficult toexplain. These dry weight differences wouldneed to be regarded with caution as thetreatment period was only 4 weeks and the pre­treatment dry weight would far exceed the dryweight increment during this period. Forexample, P. kesiya produced more and longernew roots than P. caribaea in each treatmentwith lack of difference in total root dry weight.This may be attributed to the original mass ofroots which far exceed the newly-producedroots.

Height and Diameter IncrementBoth height and diameter increment showedsignificant differences between nutrienttreatment means and between species (Table1). There was no significant difference forheight increment between F and -P, andbetween -N and -NP treatments but F and -P

TABLElResults of analysis of variance for significance of differences between treatment means for

nutrients and species and the interaction between these

Parameter utrients species Interaction(Nutrient x Species)

Root regneration (per plant)

Total number of white roots> 1.0 cm long

Total length of white roots> 2.0 cm long

Dry weight (g)

RootShootTotal plant

Increment (em)

HeightRoot collar diameter

S *** S

NS *** NS

NS NS NS

* * SS NS NS

*** NS NS

* NS NS

* P < 0.05; ** P < 0.01; ':'** P < 0.001; NS, not significant.

PERTANIKA VOL. 13 NO.2, 1990 147

EFFECTS OF NUTRIENT DEFICIENCIES ON RRP AND GROWTH OF P. CARlBAEA AND P. KESlYA SEEDLINGS

were both significantly greater than Nand ­NP treatments (Table 2).

For diameter increment, Table 2 showsthat the increments in F and -P were bothsignificantly greater than in -NP treatment. 0

significant difference was observed between F,P, and - ,and between - and - P treatments.

DISCUSSION

Within each species no significant differencein root regenerating potential (RRP) wasfound in any of the nutrient treatments.

Some effects on growth were observed. Forexample, P. kesiya seedlings grown in the -NPtreatment had significantly less shoot dryweight than seedlings of this species grown in-P treatment; P. caribaea seedlings grown in fullnutrients had significantly higher heightincrement than those grown in -N and -NPtreatments and significantly higher diameterincrement than those grown in -NP treatment.However, none of these treatments hadsignifican t effect on root regenerationalthough in P. caribaea, least root regenerationwas found in the treatments (F and-P) givingbest height growth. The possibility ofcompetition for nutrients (particularly 1 )

being involved in the balance between rootand shoot growth must be borne in mind.

Under the conditions of the experiment,however, the results indicate that plants hadadequate nutrient reserves at the commen­cement of the treatment for them not to besignificantly affected over a 4-week nutrientdeficiency treatment. The supply of Nand Pfrom the different parts of the plant, forexample from old leaves to the growing roots,was unlikely to be restricted because of thehigh mobility of the elements. Bukovac andWittwer (1957) in their study on the mobilityof radioactively labelled mineral nutrientsapplied to leaves of bean plants, classified Pto be one of the very mobile element. N canalso be considered as a relatively mobile ele­ment as suggested by experiments ondeciduous trees where in autumn aconsiderable part of the element istranslocated into the twigs before abscissionoccurs (Kramer and Kozlowski 1979).

This study confirms that the nutritional

status of seedlings is important in sustammgseedling growth, especially under poor nutrientconditions in the field, until such time asnutrient reserves in the soil can be tapped. Thenutritional status of seedlings at the time oftransplanting is largely determined by theavailability of nutrients in the nursery soil (vanden Driessche 1977). ewly-transplantedseedlings of P. radiata (Woods 1976) and Piceaabies (L.) Karst. (Machek 1972) for example,have shown improved field performance inrelation to the fertility of the soil in which theywere grown. Seedling survival and heightgrowth after transplanting may increase withimproved fertility in nursery soil (Woods 1976)but the effect of this on immediate growthresponse, i.e., RRP has not been determined.In the field, it is difficult to ascertain whethernutrient application at the time of or afterplanting is more important to seedlingperformance than is nursery soil fertility.However, it is recognised that any factor whichinhibits RRP in seedlings will reduce thechances of survival and maximum early growth(Sutton 1980; Abod and Webster 1989; 1990).

The results in this study indirectly supportthe recommendations of Endean (1967) andBrown and Hall (1968) in the use offertilizerswhere they pointed out that plant RRP is notsignificantly affected when grown in a nutrientdeficient condition for one month. Expe­riments of longer duration may be needed todetermine the time period before distinctdifferences can be observed between nutrientdeficient trees. The results is this experimentalso show that P. kesiya is superior to P. caribaeain its capacity to regenerate roots despite theshorter mean height of the former species atthe start of the experiment. It may be notedthat Kha (196'3) reported P. kesiya survives wellin competition on sites which are poor innutrients or badly degraded.

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(Received 2 August 1989)

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