Comparative response of poppy (Papaver somniferum L.) and eight crop and vegetable species to manganese excess in solution culture

The relative response of poppy (Papaver somniferum L.) and eight crop and vegetable species to excess manganese was investigated in a glasshouse, solution culture experiment. Plant yields and manganese concentrations were measured after two and six weeks growth at five levels of manganese (10–800 μM).

Poppies were highly sensitive to manganese toxicity in solution culture and reductions in shoot yield occurred at lower manganese levels in solution and at lower shoot manganese concentrations than that for the following sensitive species, ranked in order of increasing tolerance : brussels sprout, barley, green beans, lucerne and grean pea. In contrast lupins, oats and sugar beet were relatively tolerant producing about 80% or more of maximum shoot yield at the highest solution manganese level (800 μM Mn).

In this study the sensitivity of poppy, and brussels sprout, to manganese excess was attributed to their low shoot manganese “toxicity threshold values”; and their capacity to partition a high proportion of total plant manganese and dry matter to the shoot at solution manganese levels ≥ 100 μM.

The application of these results to field grown poppy is discussed in relation to interactions between manganese and other elements which modify plant tolerance to manganese excess.     

Phosphorus uptake rate and growth characteristics of wheat roots 1

Phosphorus uptake by plant roots is influenced by the plant root properties and solution P supply characteristics. These properties included (i) the relation between nutrient concentration and uptake rate, (ii) the change in uptake rate with plant age and with root age.

Information on the size of nutrient flux values and their change with increasing plant age can be used to determine the nutrient levels needed in the soil to supply nutrients rapidly enough to the root surface to minimize deficiencies. The objective of this research was to determine the relation between plant age and P absorption properties and root growth characteristics of wheat (Triticum vulgare L.) cv. Era.

Wheat was grown for periods up to 42 days in solution culture in a controlled climate chamber. Sequential harvests were made and P uptake and root morphology were measured. Shoot growth was exponential with time to 32 days and linear thereafter. Root dry weights increased linearly with time at a slower rate than shoot dry weights. Root length increased logarithmically with time (r² = 0.95; log y = 0.069x + 1.85).

With increasing plant age there was a reduction in average P uptake rate by wheat roots.     

Low-P solution culture can be used for screening root growth vigor in soil for high nutrient uptake of spring wheat varieties

Purpose: Root and root hairs of plants have been intensively studied in solution culture; however, correlation of such measurements in solution culture with development in soil is poorly understood. Therefore, the aim of this study is to study whether root and root hairs grown in solution culture can predict their behavior in soil and their correlation with macro- and micronutrients uptake of wheat genotypes.

Materials and methods: The growth of roots and root hairs as well as uptake of macro- and micronutrients of six spring wheat varieties was compared in solution culture under P stress and P abundance and in a low fertility soil.

Results and conclusions: Root length and surface area under P stress were significantly positively correlated with that in the low fertility soil, while no such correlation was apparent for root hair length and density. In absolute terms, the root length, surface area, root hair length and density of spring wheat varieties were substantially higher in soil than in solution culture, while the concentration and uptake of macro- and micronutrients in soil differed from solution culture in a complex way. The early uptake of macro- and micronutrients was intimately associated with root length and surface area as well as root hair length and density in soil but not in solution culture. Therefore, root length rather than root hair traits in low-P solution may be used to screen early root growth vigor in soil and thereby high nutrient uptake of wheat in low fertility soil.     

Effect of nitrogen and sulphur fertilizers and seed inoculation with rhizobium phaseoli on the nitrogen‐sulphur relationships of bean (phaseolus vulgaris L.)

A greenhouse experiment with beans (Phaseolus vulgaris L.) was performed in order to investigate the effect of nitrogen and sulphur application and seed inoculation on the yield, leaf area, distribution of different nitrogen and sulphur fractions and N/S ratio in shoot, fruit and root.

Inoculation of plants together with nitrogen or sulphur application produces an increase in the concentration of total nitrogen and a decrease in the accumulation of nitrate‐nitrogen and sulphate‐sulphur in shoot, fruit and root. Leaf area increased more with nitrogen than with sulphur application while the highest amounts of fruit dry matter were obtained with sulphur application.

N: S ratios obtained were different according to the part of the plant tested. Sulphur fertilization decreased the N: S ratios in shoot, fruit and root. The data obtained indicate that and adequate N: S ratio can insure maximum production of yield.     

The effect of salinity and iron application on growth and mineral uptake of sunflower (helianthus annuus L.)

In a greenhouse experiment, the effect of salinity and Fe chelate on growth and mineral uptake of sunflower (Helianthus annuus L. c.v. Record) was studied.

Sunflower plants were grown in nutrient solution with four levels of salinity (0, 1.5, 3.0 and 4.5 atm), induced by NaCl and four rates of Fe chelate (0, 0.5, 1.0 and 1.5, ppm Fe) as FeEDDHA. The experiment was a completely randomized design with treatment combinations arranged in a factorial manner with three replications.

Dry matter yield, shoot‐root ratio, leaf area, plant height and transpiration decreased as salinity increased, the effect of salinity being depressed by iron applications. Salinity reduced P, K, Ca and Mg uptake by roots as well as that of N, P, K, Ca, Mg by shoots, while Fe applications increased uptake of these elements in roots and shoots. Both salinity and iron applications increased Cl, Na and Fe uptake by roots and shoots, as expected. In most instances salinity reduced uptake of Fe, Mn and Zn by the plants while iron applications improved uptake of these elements.

The sunflower plant used in this experiment was found to be, at least partly, tolerant to salinity and decreased water availability as well as toxicity of ions. Nutritional disorders were the cause of decreased plant growth by increasing salinity of the nutrient solution. The decreased plant growth and mineral uptake, induced by salinity, were partially offset by increased iron levels in the nutrient solution.     

Differential zinc uptake and transport in sorghum varieties suited for different moisture regimes

Zinc absorption and transport were examined in M‐35 a drought resistant, and M‐47, a drought susceptible sorghum (Sorghum bicolor L. Moench) cultivar. Excised roots were employed to study the mechanisms of uptake at cellular level in these varieties.

The absorption over 0 to 130 μM ZnCl₂ followed a biphasic pattern with a second rise at 90 μM, a feature which was not observed in the absorption by roots of intact seedlings. While there were no differences in the patterns of absorption in the two cultivars, the transport to shoot in M‐35 followed a slower rate up to 90 μM than that in M‐47. When Zn uptake was examined for 6 hours, the absorption and transport showed a number of changes in phase, which were running parallel. The transport of Zn followed a higher rate in M‐47 than that in M‐35.

Phosphate decreased the uptake and also transport of Zn in both the varieties. However, Zn inhibited phosphate absorption and transport in intact seedlings differentially amongst the varieties. Further, the inhibition of Zn uptake was much less in M‐35 than in M‐47, a feature which will perhaps facilitate survival of M‐35 under water stress, a condition which would also limit phosphate availability.     

Tomato growth,nitrogen fraction and mineral composition in response to nitrate and ammonium foliar sprays 1

Tomato plants were grown in sand culture with NO₃ or NH₄ N at two levels of light. Foliar sprays at three levels of N as well as combinations of foliar and root feeding were used.

Shade increased NH₄ toxicity in plants sprayed with NH₄ but decreased the toxicity in plants receiving NH₄ through the roots. NH₄‐N greatly reduced growth and cation uptake when supplied through the roots but not with foliar application. Plants sprayed with NH₄ showed better growth, higher K, Ca, and Mg content and lower free NH₄ in shoot, compared to plants receiving NH₄ through the roots.

The overall free amino acid contents of shoots was higher for NH₄‐fed plants regardless of how the N was applied. Plants sprayed with NH₄ incorporated a greater amount of N into insoluble compounds compared with NO₃ nutrition. The N uptake per unit of leaf area was higher for plants grown under full sun light whereas N content was higher for plants grown under hade. N content in tissue increased with N concentration in foliar spray, although plants supplied with N through the roots had higher levels of free amino acids and total nitrogen.     

Iron nutrition of sunflower(Helianthus annuus L.) as affected by various levels of p and ZN

The effects of various P and Zn levels on iron nutrition of sunflower (Helianthus annuus L.c.v. Record) were studied in two separate experiments in nutrient solution under greenhouse conditions.

In the first experiment, sunflower was grown in nutrient solutions containing four levels of P(1.5, 2.5, 3.5 and 4.5 mM/l) and three levels of Fe(0.25, 0.75, and 1.5 ppm) as FeCl₃ or FeEDDHA. In the second experiment (following the first experiment), the treatments were three P levels (0.75, 1.50 and 3.00 mM/l), three Fe levels (0.25, 0.75 and 1.5 ppm) as FeEDDHA and three Zn levels (0.1, 0.2 and 0.4 ppm).

The plants receiving Fe‐chelate, except for 0.25 ppm Fe, showed no symptoms of iron chlorosis. With inorganic Fe treatments, iron chlorosis appeared after 7–10 days depending on P level, but except for 0.25 ppm Fe which remained chlorotic, plants recovered completely within 3–4 days thereafter due to pH regulating mechanism of sunflower under iron stress condition. With both sources of Fe, chlorosis was associated with high P:Fe ratio.

Increased P and Fe levels in nutrient solution resulted in general increases in the dry weights of roots and shoots. The Fe concentration of shoots, except in few instances, was not affected by P levels, indicating that the sunflower cultivar used in this experiment could utilize inorganic Fe as well as Fe‐chelate under our experimental conditions.

Increasing P levels caused significant increases in Mn content of the shoots as 0.25 and 0.75 ppm inorganic Fe³⁺. Increased Fe levels increased shoot Mn content with inorganic Fe and decreased it with Fe‐chelate. The effects of P, Fe and Zn on sunflower indicated an antagonistic effect of Zn on 1.5 ppm Fe for all P levels. Increased Zn levels in nutrient solution generally increased Zn content of the shoots without having any marked effect on their Mn content.     

Distribution of magnesium between chlorophyll and other photosynthetic functions in magnesium deficient “sun”; and “shade”; leaves of poplar

Photosynthesis of attached sun and shade grown leaves of poplar (Populus euramericana (Dode) Guinier cv. ‘Robusta') has been measured at 0.03 and 0.5% CO₂ at light limitation and light saturation. Photosynthetic rates were compared for plants grown at normal and low Mg‐supply and related to leaf Mg content.

Photosynthetic rates at high CO₂ level were affected at Mg concentration lower than about 50 μmoles/g dry leaf tissue at both photosynthetic irradiations. This was paralleled by a decrease in chlorophyll concentration. At a low CO₂ level photosynthesis was affected at the same Mg concentration but the degree of the inhibition was higher. This indicates that synthesis of chlorophyll as well as CO₂ fixation are affected at the same “critical”; Mg concentration.

Shade leaves contain more chlorophyll per unit leaf weight than sun leaves but the percentual‐ decrease of chlorophyll in Mg deficient leaves Is similar for sun and shade leaves at the same Mg leaf concentration. As a consequence, in Mg deficient shade leaves extraordinary high portions of leaf Mg are bound to chlorophyll (up to 57%; in contrast: up to 37% in sun leaves).     

Effect of soil potassium availability on soybean root and shoot growth under unrestrained rooting conditions 1

The development of soybean (Glycine max (L.) Merr.) root systems was Investigated in two greenhouse pot experiments utilizing a modified cage technique. One soil at two levels of K availability was used to observe the effect of soil K fertility level on root weight and root length in 3 cm depth Increments to 24 cm. Experiments were terminated prior to restraint of root growth by the containers. Shoot mineral accumulation and dry matter partitioning between root and shoot components were Investigated.

High K plants were shorter and had a greater root:shoot mass ratio than low K plants. A trend for greater root dry matter production in soil layers below 12 cm under high K conditions was observed. There were no differences in root length between the treatments at any depth. Tissue K content was greater in the high K treatments and this Increase was equivalents offset by decreased tissue Mg concentrations. The taller low K plants had a greater leaf area and a lower specific leaf weight, resulting in part from decreased starch content. Daily evapotranspirational water losses per pot tended to be greater under the low K availability regime. This Information led to the speculation that under low K conditions, the soybean plant may increase K accumulation by promoting transpirational water use, aiding soil K acquisition by mass flow and diffusion. Tissue carbohydrate analyses suggest greater translocation of photosynthate out of the leaf in the low K plants for use in root absorption metabolism, rather than for production of increased root dry matter and/or increased root length.     

Effect of the fraction of the root system supplied with p on p uptake and growth characteristics of wheat roots

An understanding of the phosphorus, P, uptake characteristics of plant roots is important for developing practices that improve P fertilizer efficiency. Phosphorus uptake by plant roots is influenced by plant root properties and solution P level. Since little information about the nutrient uptake characteristics of spring wheat (Triticum vulgare L.) roots is available, this research was undertaken with wheat to determine the relation between the proportion of the roots supplied with P on P influx and root growth characteristics. An experiment was conducted with wheat plants grown in solution culture in a controlled climate chamber.

Phosphorus uptake kinetics were measured on 30‐day‐old wheat using split‐root experiments. Supplying P to only part of the root system resulted in lower plant P concentration and higher I_max(maximum influx) by the roots. The I_max value of wheat roots was much lower than corn (Zea mays L.) and soybeans (Glycine max L.), but the values of Km (the solution P concentration where influx, I_n is 1/2 I_max) and C_min (the solution P concentration where influx, I_n is 1/2 I_max) were greater than those of both corn and soybean crops grown in similar experiments. Phosphorus concentrations in wheat plant's shoots and roots were higher than those for corn and soybean with the same proportions of roots in P solution. Decreasing the proportion of the roots supplied with P had no statistically significant (p = 0.05) effect on shoot dry weight. This differs from the results for corn and soybeans where it decreased significantly as the proportion of the roots exposed to P decreased. These results indicate that the effect of P placement on P uptake and on plant root growth varied among species.     

Manganese toxicity in bush bean as affected by concentration of manganese and iron in the nutrient solution

An experiment was conducted to clarify the relationship between Mn toxicity and Fe deficiency in bush snap bean (Phaseolus vulgaris L. cv. ‘Wonder Crop No. 2'). Seedlings were grown in full strength Hoagland No. 2 solution at pH 6.0 for ten days. Six concentrations of Mn as MnCl₂.4H₂O were used in combination with three concentrations of Fe as FeEDTA.

Toxicity symptoms, induced by low levels of Mn (0.1 ppm and above), included: small brown necrotic spots and veinal necrosis on primary leaves; necrosis on primary leaf petioles; interveinal chlorosis, with or without brown necrotic spots, on trifoliate leaves; and brown necrotic spots on stipules. Manganese toxicity symptoms were alleviated or prevented by increasing Fe concentration in the nutrient solution.

Manganese concentration in the leaves increased with increasing Mn and decreased with increasing Fe concentration in the nutrient solution, Iron concentration in the roots increased with increasing Fe concentration in the nutrient solution; however, Fe concentration in the leaves was not significantly affected by increasing Mn concentration in the solution culture. Manganese toxicity symptoms developed when Mn concentration in the leaves reached about 120 ppm.

A decrease in the Fe/Mn ratio in the nutrient solution resulted in a proportionate decrease in that of the leaves. Manganese toxicity symptoms occurred when the Fe/Mn ratio in the solution was 10.0 and below, or when the ratio in the leaves was less than 1.5. The ratio of Fe/Mn in the solution required for optimum growth of ‘Wonder Crop No. 2’ bean, without Mn toxicity symptoms, was in the range of 20.0 to 25.0.

Results indicate that the chlorosis on bush bean leaves induced by excessive Mn in the nutrient solution was due to excessive accumulation of Mn and not to Fe deficiency.     

Plant growth promoting bacteria increases biomass,effective constituent,and modifies rhizosphere bacterial communities of Panax ginseng

Purpose: The main aim of this study was to introduce and explore plant growth-promoting bacteria (PGPB) indigenous to ginseng, and to evaluate their ability to improve production and quality, and effect on rhizosphere niche in ginseng.

Materials and methods: Endophytic bacteria were isolated from root, stem, and leaf of ginseng from different sites and genotype in China and Korea, screened based on their beneficial properties as PGPB. Nine bacterial isolates were selected according to their plant growth properties including soluble phosphate and potassium, ammonia, auxin and siderophore producing, ACC deaminase, and antagonistic pathogen as well. Changes in ginseng after PGPB inoculation were evaluated with respect to the non-inoculated control.

Results and Conclusions: The PGPB isolates were identified as genera Bacillus, Lysinibacillus, Rhizobium, Stenotrophomonas, Erwinia, Ochrobactrum, Enterobacter and Pantoea based on 16S rRNA sequences. Inoculation of G209 and G119 increased not only plant height, root length, fresh weight, and dry weight, but also root activity and the amount of ginsenosides significantly. In particular, using the Illumina Miseq platform, the native bacterial community of rhizospheric soil maintained high community diversity and increased abundance of specific bacteria. Therefore, they may be play a crucial role in sustainable ginseng cultivating in farmland.     

Book review

Trace elements in plants by M. Ya. Shkolnik

Elsevier Science Publishers P. O. Box 330 1000 AH Amsterdam The Netherlands

Elsevier Science Publishing Company 52 Vanderbilt Ave. New York, New York 10017     

Incidence of P,Mn and B deficiencies on the levels of the whole and individual flavonoid groups in tomato leaves

Alterations occur in the normal content of total and individual flavonoids with P, Mn and B deficiencies, in tomato leaves.

P and Mn deficiencies do not alter the total flavonoid level. Nevertheless, these deficiencies lead to different contributions of each flavonoid group (flavonols, flavones and flavanones) to the whole content.

B deficiency produces a very significant increase in total flavonoid content. Compounds that contribute the most to this accumulation are flavones.     

The glycine‐glomus‐rhizobium symbiosis III. Endophyte effects on leaf carbon,nitrogen, and phosphorus nutrition

Soybean plants [Glycine max (L.) Merr.] were grown in pots and inoculated with Rhizobium japonicum and/or Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, either at planting or 20 days later. Nitrogen was supplied in the nutrient solution to plants without nitrogen‐fixing bacteria, and P was added to those without the mycorrhizal fungus. At harvest, 50 days after planting, all plants had leaves of similar dry mass. Each root symbiont grew best in the absence of the other. Growth of Glomus reflected the duration of its growing time and the presence and duration of competition from Rhizobium. Nodule weight in the tripartite associations, on the other hand, was inhibited only by the earlier introduction of Glomus.

Dipartite associations and the plants inoculated with both root symbionts at planting had the highest concentration of leaf N, and the lowest was in those inoculated with both organisms at d 20. Leaf P was highest in plants inoculated only with Rhizobium, and lowest in those tripartite associations involving any inoculation at day 20. The low values were presumably a result of the short duration of endophyte‐mediated P uptake before the plants were harvested.

Although there was almost no difference in leaf sugar concentrations, starch concentrations reflected the duration of Glomus growth, and were greatest in those plants that had supported it for the least time. Uninoculated plants contained the least starch, but produced a greater fresh mass of leaf tissue than any of the tripartite symbionts.     

Elemental leaf content and deficiency symptoms in rabbiteye blueberries: 1. Nitrogen

Rabbiteye blueberries grown in sand culture were subjected to varying levels of N fertilization (0 ‐ 81 mg N/liter) applied in aqueous solution at the rate of 250 ml/plant daily. Essential elements other than N were kept constant. Shoot growth and leaf concentration of N, P, K, Mg, Ca, Mn, Fe, Cu, B, Zn, Co, and Al were determined. Shoot growth and percent leaf N increased with increased N levels. Shoot growth increased little at N fertilization levels of 0 ‐ 9 mg/ liter but increased rapidly at higher rates. N content in leaves followed a quadratic curve, with % N in leaves increasing more rapidly from 0 to 27 mg N/liter than from 27 to 81 mg N/liter fertilization levels. Leaf concentration of K, Ca, Mg, Mn, B, and Ca decreased linearly as N levels increased. Total content of all elements increased as N fertilization increased. Visual N deficiency became increasingly evident as % N content decreased below 1.4% N.

Nitrogen, the most utilized element in plants, is usually the first to become deficient in sandy soils low in nutrient content (1). Rabbiteye blueberries (Vaccinium ashei Reade) are often grown on acidic, sandy, upland coastal plains soils that are low in cation exchange capacity, organic matter content, and available nutrients. In these acidic soils, NH₄N is more available than in neutral soils (2). The NH₄N source appears to be more suitable for blueberry growth, resulting in greater nutrient uptake, plant growth, and % N of leaf tissue than did the NO₃N sources (5,6).

Nitrogen deficiency symptoms in rabbiteye blueberries are characterized by small, yellow and/or red leaves and stunted plants (3). Since young rabbiteye plants are very sensitive to fertilizer, similar chlorosis symptoms (yellowing or reddening of leaves) can be associated with over‐fertilization, possibly due to root damage (7). Cain (2) found that leaves from healthy container‐grown highbush (V. corymbosum L.) blueberry plants contained about 2% N and higher levels of K and Ca than field‐grown plants. Greenhouse and Field studies indicate that leaf N content in rabbiteye blueberries is usually lower, ranging from about 1.5 to 1.8 (3,7,8). Increased N fertilization decreased the nutrient uptake of other essential elements (Ca and Mg) in rabbiteye blueberries (6). In highbush, Popenoe (4) indicated that a depression of P and K might occur under conditions of high N levels.

This study was initiated to ascertain the effect of NH₄N fertilization levels on uptake patterns of essential elements and to determine the relationships of N fertilization, leaf N content, plant growth, and visible deficiency symptoms.     

Root cation exchange capacity of cotton cultivars in relation to aluminum toxicity

Root cation exchange capacity (CEC) was analyzed for four cotton cultivars (Pima S‐5, Stoneville 825, Deltapine 41 and Auburn 56) within tvo species (Gossypium barbadense and G. hirsutum) grown in control (O Al) and Al (1.5 mg/l) solution. Pima S‐5, a G. barbadense variety, had significantly (P < 0.10) lower root CEC than G. hirsutum cultivars in control (O Al) solution. Root CEC of Stoneville 825 was numerically but not significantly lower than Auburn 56 and Deltapine Al in control solution. Root CEC was significantly reduced in all cultivars when grown in Al solution. Compared to controls, Pima S‐5 and Stoneville 825 had either numerically or significantly less reduction in root CEC than Auburn 56 or Deltapine 41 in Al solution. Aluminum content of roots after CEC analysis was numerically greater in the former cultivars than the latter.

The lower root CEC of Pima S‐5 and Stoneville 825 in non‐toxic conditions could provide an initially greater Al tolerance when roots grow into marginally Al toxic soil. Under sustained, Al toxic conditions, root CEC becomes altered and is more of an indirect indicator of root growth as affected by as yet undetermined Al tolerance mechanism(s).

The steady‐state technique to determine root CEC virtually eliminated the inherent problems of CO. effects on pH and titrating to an end point in a specific period of time in a dynamic system.     

Soil temperature affects element uptake by sorghum

The influence of soil temperature on nutrient accumulation in aerial portions of sorghum plants was evaluated in a greenhouse experiment. Plants were grown in 20‐liter containers at cooled and ambient soil temperatures of 20 and 25C, respectively, and were harvested at the 8‐ and 12‐leaf stages of development for yield and nutrient analysis.

At the 8‐leaf stage, sorghum plants subjected to 25C were significantly higher in concentration of N, P, K, Mg, and Cu, but were significantly lower in Ca. Soil temperature did not significantly affect concentration of Zn, Fe, and Mn. At the 12‐leaf stage, sorghum plants grown in the warm soil temperature treatment were lower in concentration of N, K, Ca, Mg, Zn, Fe, Mn, and Cu than plants grown in the cooled‐soil treatment. Phosphorus showed a negative response to increased temperature.

It was concluded that further research relating element uptake and translocation to temperature is needed. Element accumulation in the roots, stems, leaves, and floral and seed portions of the plant should be included. In addition, the interaction between plant age and element concentration should be studied more thoroughly. Both this study and the published literature indicate that this interaction is significant for many of the elements.     

Sorghum genotype differences in phosphorus uptake rate and distribution in plant parts

Relatively low amounts of the phosphorus (P) added to soils is recovered by plants. Many plants show differences in their ability to take up and use P, but the mechanisms for these differences are not fully understood. The purpose of this study was to determine differences among sorghum [Sorghum bicolor (L.) Moench] genotypes for P uptake rates and distribution in plant parts.

Differences in P uptake rates were determined for six sorghum genotypes at 24, 38, and 52 days of age at three P levels. Larger differences were noted among genotypes in 24‐day‐old plants than for older plants. Uptake rates were 6‐ to 14‐times higher (dependent on genotype) in 24‐day‐old plants than in 52‐day‐old plants. NB9040 which had the highest dry matter yield at each age had the lowest rate of P uptake, and CK60‐Korgi which had the lowest dry matter yield at each age had the highest rate of P uptake.

Only small differences were noted among genotypes for distribution of P within plant parts for younger plants. Older plants showed differences in P distribution, and NB9040 translocated more P from lower to upper leaves, had higher efficiency ratios (dry matter produced/unit P), and had a larger root system than CK60‐Korgi.

The sorghum genotypes that produced more dry matter under low P conditions had lower uptake rates of P and had the ability to distribute P from older to younger developing tissues. When grown in soils, plants that have lower P uptake rates, greater ability to distribute P, and larger root systems may not deplete P from soil solutions as rapidly, could explore more soil, and possibly use P more efficiently than plants that do not possess these traits.