Phosphorus starvation boosts carboxylate secretion in P-deficient genotypes of Lupinus angustifolius with contrasting root structure

2013 ◽  
Vol 64 (6) ◽  
pp. 588 ◽  
Author(s):  
Ying L. Chen ◽  
Vanessa M. Dunbabin ◽  
Art J. Diggle ◽  
Kadambot H. M. Siddique ◽  
Zed Rengel
Keyword(s):  
Root System ◽  
Root Architecture ◽  
Lateral Roots ◽  
P Uptake ◽  
Lupinus Angustifolius ◽  
Grain Legume ◽  
P Deficiency ◽  
P Acquisition ◽  
P Concentration ◽  
Carboxylate Exudation

Lupinus angustifolius L. (narrow-leafed lupin) is an important grain legume crop for the stockfeed industry in Australia. This species does not form cluster roots regardless of phosphorus (P) nutrition. We hypothesise that this species may have adaptive strategies for achieving critical P uptake in low-P environments by altering shoot growth and root architecture and secreting carboxylates from roots. Three wild genotypes of L. angustifolius with contrasting root architecture were selected to investigate the influence of P starvation on root growth and rhizosphere carboxylate exudation and their relationship with P acquisition. Plants were grown in sterilised loamy soil supplied with zero, low (50 μm) or optimal (400 μm) P for 6 weeks. All genotypes showed a significant response in shoot and root development to varying P supply. At P deficit (zero and low P), root systems were smaller and had fewer branches than did roots at optimal P. The amount of total carboxylates in the rhizosphere extracts ranged from 3.4 to 17.3 μmol g–1 dry root. The total carboxylates comprised primarily citrate (61–78% in various P treatments), followed by malate and acetate. Genotype #085 (large root system with deep lateral roots) exuded the greatest amount of total carboxylates to the rhizosphere for each P treatment, followed by #016 (medium root system with good branched lateral roots) and #044 (small root system with short and sparse lateral roots). All genotypes in the low-P treatment significantly enhanced exudation of carboxylates, whereas no significant increase in carboxylate exudation was observed in the zero-P treatment. Small-rooted genotypes had higher P concentration than the medium- and large-rooted genotypes, although larger plants accumulated higher total P content. Large-rooted genotypes increased shoot P utilisation efficiency in response to P starvation. This study showed that narrow-leafed lupin genotypes differing in root architecture differed in carboxylate exudation and P uptake. Our finding suggested that for L. angustifolius there is a minimum plant P concentration below which carboxylate exudation is not enhanced despite severe P deficiency. The outcomes of this study enhance our understanding of P acquisition strategies in L. angustifolius genotypes, which can be used for the selection of P-efficient genotypes for cropping systems.

scholarly journals Cost-Benefit Analysis of the Upland-Rice Root Architecture in Relation to Phosphate: 3D Simulations Highlight the Importance of S-Type Lateral Roots for Reducing the Pay-Off Time

2021 ◽  
Vol 12 ◽  
Author(s):  
Daniel Gonzalez ◽  
Johannes Postma ◽  
Matthias Wissuwa
Keyword(s):  
Root System ◽  
Lateral Roots ◽  
Root Hairs ◽  
P Uptake ◽  
Root Tissue ◽  
Rice Root ◽  
P Deficiency ◽  
Nodal Roots ◽  
Nodal Root ◽  
Off Time

The rice root system develops a large number of nodal roots from which two types of lateral roots branch out, large L-types and fine S-types, the latter being unique to the species. All roots including S-types are covered by root hairs. To what extent these fine structures contribute to phosphate (P) uptake under P deficiency was investigated using a novel 3-D root growth model that treats root hairs as individual structures with their own Michaelis-Menten uptake kinetics. Model simulations indicated that nodal roots contribute most to P uptake followed by L-type lateral roots and S-type laterals and root hairs. This is due to the much larger root surface area of thicker nodal roots. This thickness, however, also meant that the investment in terms of P needed for producing nodal roots was very large. Simulations relating P costs and time needed to recover that cost through P uptake suggest that producing nodal roots represents a considerable burden to a P-starved plant, with more than 20 times longer pay-off time compared to S-type laterals and root hairs. We estimated that the P cost of these fine root structures is low enough to be recovered within a day of their formation. These results expose a dilemma in terms of optimizing root system architecture to overcome P deficiency: P uptake could be maximized by developing more nodal root tissue, but when P is growth-limiting, adding more nodal root tissue represents an inefficient use of the limiting factor P. In order to improve adaption to P deficiency in rice breeding two complementary strategies seem to exist: (1) decreasing the cost or pay-off time of nodal roots and (2) increase the biomass allocation to S-type roots and root hairs. To what extent genotypic variation exists within the rice gene pool for either strategy should be investigated.

scholarly journals Arsitektur akar bibit kelapa sawit yang diinokulasi beberapa cendawan mikoriza arbuskula Root architecture of oil palm seedling inoculated with selected arbuscular mycorrhizal fungi

2016 ◽  
Vol 71 (1) ◽  
Author(s):  
Happy WIDIASTUTI ◽  
Edi GUHARDJA ◽  
Nampiah SUKARNO ◽  
Latifah KOSIM DARUSMAN ◽  
Didiek Hadjar GOENADI ◽  
...  
Keyword(s):  
Root System ◽  
Oil Palm ◽  
Root Morphology ◽  
Mycorrhizal Fungi ◽  
Root Architecture ◽  
Acid Soil ◽  
Am Fungi ◽  
P Uptake ◽  
Fungal Colonization ◽  
Gigaspora Margarita

Summary Oil palm is mostly cultivated in acid soil. The growth constraint of plant in acid soil is the limited availability of phosphorus (P) nutrient. Improvement of root system morphology and architecture have an important aspect since P is immobilized nutrient. Colonization of oil palm by rrbuscular mycorrhizal fungi increase the P uptake of plant. However, there is no information related to the effect of AM fungal colonization on oil palm root morphology and architecture.        A research has been conducted to asses the effect of colonization of two species of AM fungi on root system morphology and architecture of oil palm seedling. The research was conducted using Cikopomayak acid soil as medium in simple glass chamber. The plant material was from Indonesian Oil Palm Research Institute, Medan while AM fungal inoculum was produced using pot culture. Six treatments assesed are combination of three levels of  AM fungi inoculation (without inoculation with, Acaulospora tuberculata and Gigaspora margarita) and two levels of  fertilization (without, and with fertilizer). The result showed that colonization of AM fungi could change the root system morphology, and root architecture. The root fresh weight, root dry weight, length, and volume were significantly higher with the AM fungi colonization especially A. tuberculata inoculation. However, specific root weight was not significantly different between inoculated and uninoculated. The enhancement was significantly observed 26 weeks after inoculation. Biside that, proportion of secondary root of oil palm inoculated with AM fungi was higher compared to primary root. Fertilization tend to reduced root growth. Fertilization reduced significantly root shoot ratio of inoculated as well as uninoculated seedlings. The rooting volume was higher in inoculated seedling compared to uninoculated. The highest enhancement of N, P, and K uptake was observed 26 weeks after inoculation. The better root morphology and architecture might be one mechanisms of AM fungi colonized oil palm seedlings in increasing P uptake. Ringkasan Umumnya tanaman kelapa sawit ditanam pada tanah masam. Hambatan pertumbuhan tanaman pada tanah masam adalah terbatasnya ketersediaan nutrisi P (fosforus). Oleh sebab itu perbaikan sistem morfologi dan arsitektur akar memiliki aspek yang penting disebabkan P merupakan nutrisi yang tidak mudah bergerak. Kolonisasi tanaman kelapa sawit dengan cendawan  mikoriza arbuskula (CMA) akan meningkatkan penyerapan P oleh tanaman.  Namun, hubungan antara simbiosis  CMA dengan arsitektur perakaran kelapa sawit belum diketahui. Penelitian ini dilakukan untuk mempelajari pengaruh kolonisasi dua spesies CMA pada sistem morfologi dan arsitektur akar bibit tanaman kelapa sawit. Percobaan  dilakukan menggunakan tanah masam Cikopomayak yang mengandung Al tinggi sebagai medium dalam kultur pot kaca yang sederhana. Kecambah kelapa sawit berasal dari Pusat Penelitian Kelapa Sawit (PPKS), Medan,  sedangkan inokulum CMA diproduksi menggunakan kultur pot. Enam perlakuan yang diuji merupakan kombinasi tiga jenis inokulasi CMA ( tanpa inokulasi, inokulasi dengan Acaulospora tuberculata dan Gigaspora margarita) serta dua tingkat pemupukan (tanpa, dan dengan pemupukan). Hasil yang diperoleh menunjukkan bahwa inokulasi CMA merubah sistem morfologi dan arsitektur perakaran. Bobot basah, bobot kering, panjang dan volume akar nyata lebih tinggi pada tanaman yang dikolonisasi CMA khususnya A. tuberculata. Namun berat akar spesifik tidak beda nyata antara yang diinokulasi dan tanpa inokulasi. Peningkatan berat akar sangat nyata setelah 26 hari diinokulasi. Di samping itu proporsi akar sekunder lebih tinggi dibandingkan dengan akar primer pada  tanaman kelapa sawit yang diinokulasi CMA. Pemupukan pada umumnya menurunkan pertumbuhan akar dan secara nyata menurunkan nisbah akar pucuk. Volume perakaran lebih besar pada bibit kelapa sawit yang diinokulasi dibandingkan dengan yang tidak diinokulasi.  Peningkatan serapan  N, P,  dan  K tertinggi teramati 26 minggu setelah inokulasi. Morfologi perakaran yang lebih baik demikian pula arsitektur perakaran mungkin merupakan mekanisme bibit kelapa sawit bermikoriza dalam meningkatkan serapan P.

scholarly journals Development of Root Architecture in Thirty-seven Tree Species of Field Grown Nursery Stock1

2020 ◽  
Vol 38 (4) ◽  
pp. 143-148
Author(s):  
G. W. Watson ◽  
A.M. Hewitt
Keyword(s):  
Root System ◽  
Root Development ◽  
Lateral Root ◽  
Root Architecture ◽  
Lateral Roots ◽  
Acer Rubrum ◽  
Acer Pseudoplatanus ◽  
Lateral Root Development ◽  
Nursery Production ◽  
One Year

Abstract The number and size of lateral roots of a tree seedling can be evaluated visually, and could potentially be used to select plants with better root systems early in nursery production. To evaluate how root architecture develops in young trees, root architecture of 37 species of trees was compared at two stages of development: as harvested seedlings, and then one year after replanting. The total number of lateral roots and the number of roots >2mm (0.08 in) diameter that were present on the portion of the taproot remaining on seedlings after standard root pruning were recorded. Neither could consistently predict the number of lateral roots on the root system one year after replanting. Development of roots (sum of diameters) regenerated from the cut end of the seedling taproot was equal or greater than lateral root development in 84 percent of evaluated species. Even when regenerated root development was significantly less than lateral root development, the regenerated roots still comprised up to 44 percent of the root system. Regenerated roots from the cut end of the taproot can become a major component of the architecture of the structural root system in nursery stock. Index words: structural roots, nursery production, root regeneration. Species used in this study: European black alder (Alnus glutinosa Gaertn.), green ash (Fraxinus pennsylvanica Marshall), quaking aspen (Populus tremuloides Michx.), European white birch. (Betula pendula Roth), river birch (Betula nigra L.), black locust (Robinia pseudoacacia L.), northern catalpa (Catalpa speciosa (Warder) Warder ex Engelm.), Mazzard cherry [Prunus avium [L.) L.], chokecherry (Prunus virginiana L.), American elm (Ulmus americana L.), Siberian elm (Ulmus pumilia L.), goldenchain tree (Laburnum anagyroides Medik.), northern hackberry (Celtis occidentalis L.), Cockspur hawthorn (Crateagus crus-galli L.), single seed hawthorn (Crateagus monogyna Jacq.), honeylocust (Gleditsia tricanthos L.), Japanese pagodatree [Sophora japonica (L.) Schott], Katsura tree (Cercidiphyllum japonicum Siebold & Zucc.), Kentucky coffee tree [Gymnocladus dioicus (L.) K. Koch], littleleaf linden (Tilia cordata Mill.), boxelder (Acer negundo L.), hedge maple (Acer campestre L.), Norway maple (Acer platanoides L.), red maple (Acer rubrum L.), silver maple (Acer saccharinum L.), sugar maple (Acer saccharum Marshall), sycamore maple (Acer pseudoplatanus L.), English Oak (Quercus robur L.), northern red oak (Quercus rubra L.), Siberian peashrub (Caragana arborescens Lam.), American plum (Prunus Americana Marshall ), Myrobalan plum (Prunus cerasifera Ehrh.), redbud (Cercis Canadensis L.), Russian olive (Elaeagnus angustifoliaI L.), tuliptree (Liriodendron tulipifera L.), black walnut (Juglans nigra L.), Japanese zelkova (Zelkova serrata (Thunb.) Makino).

scholarly journals ROOT CO2 EFFECTS ON THE PEACH ROOT SYSTEM

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1119b-1119
Author(s):  
D. M. Glenn ◽  
W. V. Welker
Keyword(s):  
Root System ◽  
Shoot Growth ◽  
Root Length Density ◽  
Lateral Roots ◽  
Field Studies ◽  
P Uptake ◽  
Solution Ph ◽  
Dry Matter Partitioning ◽  
Plant Respiration ◽  
Root Axis

Carbon dioxide is produced by microbial and plant respiration and accumulates in the soil. In previous field studies, CO2 levels were higher under a killed sod soil management system, relative to cultivation and herbicide systems (1.8 vs 0.8 and 1.0%), respectively. Our objective in these studies was to measure the effect of elevated levels of root system CO2 on root and shoot growth and nutrient uptake. Using soil and hydroponic systems in greenhouse studies, we maintained root system CO2 levels between 1.5 and 2.5%. Control CO2 levels were less than 1%. Root length density and dry matter partitioning to the root system were increased by root CO2 in soil and hydroponic studies; shoot growth was unaffected. In hydroponic culture, root CO2 increased P uptake, solution pH, root volume and the number of lateral roots/cm root axis. Elevated levels of CO2 in the root system stimulated root growth in both the soil and hydroponic studies.

scholarly journals Root Respiration and Phosphorus Nutrition of Tomato Plants Grown at a 36 °C Root-zone Temperature

1997 ◽  
Vol 122 (2) ◽  
pp. 175-178 ◽  
Author(s):  
Kimberly A. Klock ◽  
Henry G. Taber ◽  
William R. Graves
Keyword(s):  
Phosphatase Activity ◽  
Root Respiration ◽  
Root Zone ◽  
Root Surface ◽  
P Uptake ◽  
Root Zone Temperature ◽  
Tomato Plants ◽  
P Acquisition ◽  
P Concentration ◽  
Over Time

Growth of tomato (Lycopersicon esculentum Mill.) plants decreases at root-zone temperatures (RZTs) >30 °C, but no research has been conducted on the effects of changes in root respiration on P acquisition at supraoptimal RZT. We monitored the changes every 3 to 5 days in root respiration, root surface phosphatase activity, and P acquisition of `Jet Star' tomato plants grown in Hoagland's no. 1 solution held at 25 and 36 °C RZT for 19 days. Root respiration rate in plants grown at 25 °C increased linearly from RZT initiation to day 12, but there was no difference in respiration between days 12 and 19. Root respiration at 36 °C, however, increased from RZT initiation to day 8 and then decreased. Shoot P concentration and root phosphatase activity for plants grown at 25 °C did not change during the experiment. Shoot P concentration for plants at 36 °C, however, linearly decreased over time, and root phosphatase activity linearly increased over time. Decreased shoot growth and demand for P along with decreased root respiration after day 8 probably resulted in the decreased P uptake and shoot P concentration in plants grown at 36 °C RZT.

Phosphorus efficiency in pasture species. VIII. Ontogeny, growth, P acquisition and P utilization of Italian ryegrass and phalaris under P deficient and P sufficient conditions

1994 ◽  
Vol 45 (3) ◽  
pp. 669 ◽  
Author(s):  
PD Kemp ◽  
GJ Blair
Keyword(s):  
Biomass Production ◽  
Sufficient Conditions ◽  
P Uptake ◽  
Italian Ryegrass ◽  
Phosphorus Efficiency ◽  
Total Biomass ◽  
P Deficiency ◽  
P Acquisition ◽  
P Utilization ◽  
Temporal Basis

The P efficiency of Italian ryegrass (Lolium multiflorum Lamk. cv Grasslands Tama) and phalaris (Phalaris aquatica L. cv Sirosa) was compared on both a temporal and ontogenetic basis. As ontogeny and growth are interrelated, such a comparison allowed the growth and physiological responses to P level of the two species to be separated from responses due to the species being at different ontogenetic stages at the time of comparison. Plants were grown from seed through to anthesis under P deficient and P sufficient conditions in soil in a glasshouse. The ontogenies of Italian ryegrass and phalaris were similar, but the rate of development of Italian ryegrass was greater at both P rates. P deficiency resulted in arrested reproductive development in phalaris. At both P levels shoot, root and total biomass and net P uptake per plant by Italian ryegrass were greater than by phalaris when the two species were compared on a temporal basis, but when compared on an ontogenetic basis the two species were similar. There were some differences in the allocation of P between the acid-soluble P, lipid P, and residue P fractions, but biomass production was not determined by the efficiency of P utilization. The superior biomass production of Italian ryegrass on a temporal basis was due to its greater seed size and rate of ontogeny rather than differences in photosynthetic rate, unit leaf rate, leaf area ratio or shoot: root ratio. Similarly, the greater P uptake per plant of Italian ryegrass on a temporal basis was driven by its greater plant size and faster root extension rate rather than by P uptake per unit root length. The level of vesicular arbuscular mycorrhizal (VAM) infection in the roots of the two species was similar under P deficiency but greater in phalaris under P sufficient conditions. Overall, the different temporal responses to P of Italian ryegrass and phalaris were largely related to their different rates of ontogeny and the interrelationships between ontogeny and growth rate rather than to differences in their physiology in relation to P acquisition and utilization.

scholarly journals Response of Young Olive Plants (Olea europaea) to Phosphorus Application

HortScience ◽  
2016 ◽  
Vol 51 (9) ◽  
pp. 1167-1170 ◽  
Author(s):  
María José Jiménez-Moreno ◽  
Ricardo Fernández-Escobar
Keyword(s):  
Shoot Growth ◽  
Phosphorus Uptake ◽  
P Uptake ◽  
Zn Deficiency ◽  
P Deficiency ◽  
P Concentration ◽  
Quadratic Response ◽  
P Application ◽  
Phosphorus Application ◽  
Leaf P

Mist-rooted ‘Picual’ olive cuttings growing in 1.1-L pots containing a mixture of washed sand and perlite were used to induce symptoms of phosphorus (P) deficiency and toxicity and to determine the nutritional status to which these symptoms occur. Plants were growing in a growth chamber at 25 °C day/15 °C night with a 14-hour photoperiod. From late spring to the autumn, plants were placed in a shade house protected from the rain. In the first experiment, plants received the application of 0, 100, 200, or 400 ppm P, and in the second experiment, 0, 12.5, 25, 50, 100, or 200 ppm P. Shoot growth was measured weekly and leaf samples were collected at different dates to determine P concentration. At the end of each experiment, plants were harvested and P was determined to obtain the P uptake by the plants. Phosphorus uptake efficiency (PUE) was estimated as PUE = (P uptake/P applied) × 100. P content increased in plants with the amount of P applied, and accumulated mainly in the roots. Vegetative growth showed a quadratic response, indicating a reduction of growth at the lowers and highest doses of P application. Leaf P concentration below or above which shoot growth was reduced was 0.11% to 0.13%. Symptoms of P deficiency and toxicity were observed in only a few plants. Leaf P concentration of deficient plants was 0.025%, and that of toxicity 0.21%. Toxicity symptoms were similar to that of zinc (Zn) deficiency. PUE was very low, 1.34% to 4.45%, suggesting the low P requirements of the olive.

scholarly journals Novel Genes and Genetic Loci Associated With Root Morphological Traits, Phosphorus-Acquisition Efficiency and Phosphorus-Use Efficiency in Chickpea

2021 ◽  
Vol 12 ◽  
Author(s):  
Mahendar Thudi ◽  
Yinglong Chen ◽  
Jiayin Pang ◽  
Danamma Kalavikatte ◽  
Prasad Bajaj ◽  
...  
Keyword(s):  
Linear Model ◽  
Arabinogalactan Protein ◽  
Manganese Concentration ◽  
Grain Legume ◽  
Novel Genes ◽  
P Deficiency ◽  
P Use Efficiency ◽  
P Acquisition ◽  
A Genome ◽  
Use Efficiency

Chickpea—the second most important grain legume worldwide—is cultivated mainly on marginal soils. Phosphorus (P) deficiency often restricts chickpea yields. Understanding the genetics of traits encoding P-acquisition efficiency and P-use efficiency will help develop strategies to reduce P-fertilizer application. A genome-wide association mapping approach was used to determine loci and genes associated with root architecture, root traits associated with P-acquisition efficiency and P-use efficiency, and any associated proxy traits. Using three statistical models—a generalized linear model (GLM), a mixed linear model (MLM), and a fixed and random model circulating probability unification (FarmCPU) —10, 51, and 40 marker-trait associations (MTAs), respectively were identified. A single nucleotide polymorphism (SNP) locus (Ca1_12310101) on Ca1 associated with three traits, i.e., physiological P-use efficiency, shoot dry weight, and shoot P content was identified. Genes related to shoot P concentration (NAD kinase 2, dynamin-related protein 1C), physiological P-use efficiency (fasciclin-like arabinogalactan protein), specific root length (4-coumarate–CoA ligase 1) and manganese concentration in mature leaves (ABC1 family protein) were identified. The MTAs and novel genes identified in this study can be used to improve P-use efficiency in chickpea.

scholarly journals Understanding Root Systems to Improve Seedling Quality

1998 ◽  
Vol 8 (4) ◽  
pp. 544-549 ◽  
Author(s):  
Silvana Nicola
Keyword(s):  
Root Growth ◽  
Root System ◽  
Seedling Growth ◽  
Root Morphology ◽  
Root Architecture ◽  
Lateral Roots ◽  
Root Systems ◽  
The Third ◽  
Observation Methods ◽  
Different Types

Root architecture can be very important in plant productivity. The importance of studies on root morphology and development is discussed to improve seedling growth. Root systems of dicotyledonous species are reviewed, with emphasis on differences between growth of basal and lateral roots. The presence of different types of roots in plant species suggests possible differences in function as well. The architecture of a root system related to its functions is considered. Classical methods for studying root systems comprise excavation of root system, direct observation, and indirect analyses. While the first method is destructive and the third is effective in understanding root architecture only on a relatively gross scale, observation methods allow the scientist a complete a nondestructive architectural study of a root system. The three groups are reviewed related to their potential to give valuable information related to the root architecture and development of the seedling, with emphasis on the availability of a medium-transparent plant-growing system, enabling nondestructive daily observations and plant measurements under controlled environmental conditions. Effects of CO2 enrichment on seedling growth is reviewed, emphasizing the effects of CO2 on root growth.

scholarly journals Arsitektur akar bibit kelapa sawit yang diinokulasi beberapa cendawan mikoriza arbuskula Root architecture of oil palm seedling inoculated with selected arbuscular mycorrhizal fungi

2016 ◽  
Vol 71 (1) ◽  
Author(s):  
Happy WIDIASTUTI ◽  
Edi GUHARDJA ◽  
Nampiah SUKARNO ◽  
Latifah KOSIM DARUSMAN ◽  
Didiek Hadjar GOENADI ◽  
...  
Keyword(s):  
Root System ◽  
Oil Palm ◽  
Root Morphology ◽  
Mycorrhizal Fungi ◽  
Root Architecture ◽  
Acid Soil ◽  
Am Fungi ◽  
P Uptake ◽  
Fungal Colonization ◽  
Gigaspora Margarita

Summary Oil palm is mostly cultivated in acid soil. The growth constraint of plant in acid soil is the limited availability of phosphorus (P) nutrient. Improvement of root system morphology and architecture have an important aspect since P is immobilized nutrient. Colonization of oil palm by rrbuscular mycorrhizal fungi increase the P uptake of plant. However, there is no information related to the effect of AM fungal colonization on oil palm root morphology and architecture.        A research has been conducted to asses the effect of colonization of two species of AM fungi on root system morphology and architecture of oil palm seedling. The research was conducted using Cikopomayak acid soil as medium in simple glass chamber. The plant material was from Indonesian Oil Palm Research Institute, Medan while AM fungal inoculum was produced using pot culture. Six treatments assesed are combination of three levels of  AM fungi inoculation (without inoculation with, Acaulospora tuberculata and Gigaspora margarita) and two levels of  fertilization (without, and with fertilizer). The result showed that colonization of AM fungi could change the root system morphology, and root architecture. The root fresh weight, root dry weight, length, and volume were significantly higher with the AM fungi colonization especially A. tuberculata inoculation. However, specific root weight was not significantly different between inoculated and uninoculated. The enhancement was significantly observed 26 weeks after inoculation. Biside that, proportion of secondary root of oil palm inoculated with AM fungi was higher compared to primary root. Fertilization tend to reduced root growth. Fertilization reduced significantly root shoot ratio of inoculated as well as uninoculated seedlings. The rooting volume was higher in inoculated seedling compared to uninoculated. The highest enhancement of N, P, and K uptake was observed 26 weeks after inoculation. The better root morphology and architecture might be one mechanisms of AM fungi colonized oil palm seedlings in increasing P uptake. Ringkasan Umumnya tanaman kelapa sawit ditanam pada tanah masam. Hambatan pertumbuhan tanaman pada tanah masam adalah terbatasnya ketersediaan nutrisi P (fosforus). Oleh sebab itu perbaikan sistem morfologi dan arsitektur akar memiliki aspek yang penting disebabkan P merupakan nutrisi yang tidak mudah bergerak. Kolonisasi tanaman kelapa sawit dengan cendawan  mikoriza arbuskula (CMA) akan meningkatkan penyerapan P oleh tanaman.  Namun, hubungan antara simbiosis  CMA dengan arsitektur perakaran kelapa sawit belum diketahui. Penelitian ini dilakukan untuk mempelajari pengaruh kolonisasi dua spesies CMA pada sistem morfologi dan arsitektur akar bibit tanaman kelapa sawit. Percobaan  dilakukan menggunakan tanah masam Cikopomayak yang mengandung Al tinggi sebagai medium dalam kultur pot kaca yang sederhana. Kecambah kelapa sawit berasal dari Pusat Penelitian Kelapa Sawit (PPKS), Medan,  sedangkan inokulum CMA diproduksi menggunakan kultur pot. Enam perlakuan yang diuji merupakan kombinasi tiga jenis inokulasi CMA ( tanpa inokulasi, inokulasi dengan Acaulospora tuberculata dan Gigaspora margarita) serta dua tingkat pemupukan (tanpa, dan dengan pemupukan). Hasil yang diperoleh menunjukkan bahwa inokulasi CMA merubah sistem morfologi dan arsitektur perakaran. Bobot basah, bobot kering, panjang dan volume akar nyata lebih tinggi pada tanaman yang dikolonisasi CMA khususnya A. tuberculata. Namun berat akar spesifik tidak beda nyata antara yang diinokulasi dan tanpa inokulasi. Peningkatan berat akar sangat nyata setelah 26 hari diinokulasi. Di samping itu proporsi akar sekunder lebih tinggi dibandingkan dengan akar primer pada  tanaman kelapa sawit yang diinokulasi CMA. Pemupukan pada umumnya menurunkan pertumbuhan akar dan secara nyata menurunkan nisbah akar pucuk. Volume perakaran lebih besar pada bibit kelapa sawit yang diinokulasi dibandingkan dengan yang tidak diinokulasi.  Peningkatan serapan  N, P,  dan  K tertinggi teramati 26 minggu setelah inokulasi. Morfologi perakaran yang lebih baik demikian pula arsitektur perakaran mungkin merupakan mekanisme bibit kelapa sawit bermikoriza dalam meningkatkan serapan P.

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