Mineral Nutrient Partitioning Research Articles

Influence of cutting time interval and season on productivity, nutrient partitioning, and forage quality of blue panicgrass (Panicum antidotale Retz.) under saline irrigation in Southern region of Morocco.

Salinity has become a major issue in various parts of the world negatively impacting agricultural activities and leading to diminished crop potential and lower yields. Such situation calls for urgent interventions such as adopting salt-tolerant crops to fill the gap in food and feed availability. Blue panicgrass (Panicum antidotale Retz.) is a promising salt-tolerant forage crop that has shown an appropriate adaptation and performance in the saline, arid, and desertic environments of southern Morocco. However, for obtaining a highest forage productivity with nutritional quality, optimization of the cutting interval is required. Thus, the objective of this study was to determine the optimal cutting time interval allowing high forage production and quality under high salinity conditions. This experiment was conducted over one entire year covering the summer and winter seasons. The effect of five cutting time intervals on selected agro-morphological traits, crop productivity, mineral nutrient accumulation, and forage quality of blue panicgrass in the region of Laayoune, southern Morocco. The finding of this study recommend that cutting blue panicgrass every 40 days maximized the annual fresh and dry forage yield as well as the protein yield, which reached 74, 22, and 2.9 t/ha, respectively. This study also revealed a significant effect of the season on both productivity and quality. However, forage yield declined during the winter and increased during the summer, while protein content increased during winter compared to summer. The mineral nutrient partitioning between shoots and roots, especially the K+/Na+ ratio, indicated that blue panicgrass has salt tolerance mechanism as it excluded sodium from the roots and compartmentalized it in the leaves. In conclusion, there is a potential of blue panicgrass on sustaining forage production under salt-affected drylands, as demonstrated by the response to two key questions: (a) a technical question to farmers for its adoption such as at which interval should blue panicgrass be harvested maximizing both forage yield and quality? And (b) a scientific question on how does blue panicgrass maintain high K+/Na+ ratio to cope with salinity stress?

Biomass and mineral nutrient partitioning among self-pollinated and cross-pollinated fruit on the same strawberry plant.

Pollen-parent effects on fruit size and quality have been found previously among competing self-pollinated and cross-pollinated fruit on the same Redlands Joy strawberry plant. These effects occur independently of the percentage of fertilized seeds on the fruit, but the expression of these effects on fruit size and some aspects of quality are greatest when calcium is in shortest supply. Here, we aimed to clarify at what developmental stages the self-pollinated and cross-pollinated fruit diverge in size and quality and whether differences between self-pollinated and cross-pollinated fruit are due to early differences in nutrient accumulation. Fruit were harvested at 1, 2 and 3 weeks after hand-pollination and at full ripeness, approximately 4 weeks after hand-pollination. We measured fruit mass, length, diameter, colour, and the concentrations of aluminium, boron, calcium, copper, iron, nitrogen, magnesium, manganese, sodium, phospho-rous, potassium and zinc. Temporary increases in fruit mass, length or diameter due to cross-pollination were evident at 1 or 2 weeks after pollination. Consistent increases in size and skin darkness from cross-pollination emerged in the final week of fruit development. We found little evidence that self-pollinated and cross-pollinated fruit differed in mineral nutrient accumulation at any stage of fruit development. The results demonstrate that cross-pollination effects on strawberry fruit size are evident briefly during early fruit growth but emerge mainly during the final week of fruit development. The effects of cross-pollination on fruit size are not the result of early differences in mineral nutrient accumulation between self-pollinated and cross-pollinated fruit.

Dry Matter Accumulation, Seasonal Uptake and Partitioning of Mineral Nutrients by Vitis vinifera L. cv. Sultanina Grapevines in the Lower Orange River Region of South Africa - A Preliminary Investigation

Table grapes are harvested from November until early February in the Orange River Region of SouthAfrica, where a functional leaf canopy is present for up to six months of post-harvest. Seasonal uptakeand partitioning of mineral nutrients by ‘Sultanina’ grapevines in this long-season area were quantifiedin a preliminary investigation. Entire grapevines growing on two different soil types were sampled duringthe growing season. On sandy soil, further from the river, grapevine vigour was not excessive; however,on the fertile alluvial soil vigour was higher with active post-harvest re-growth. At budbreak, reserve Nplayed an important role on the sandy soil, while it was less important on the alluvial one. During the postharvestperiod, 34.3% of the annual N-requirement was absorbed by grapevines cultivated on sandy soilat post-harvest, while only 17.0% was absorbed on the alluvial soil. Approximately 4.0 kg N was utilizedfor the production of one ton of fresh grapes. A major fraction of the annual P-requirement (41.9%) wasabsorbed post-harvest by grapevines on the sandy soil. Grapevines on alluvial soil absorbed more P atpre-harvest; however, P was somehow lost post-harvest. Comparable amounts of K and Mg were absorbedby both selections of grapevines. Sandy soil grapevines absorbed K and Mg at post-harvest, while a netloss occurred for those of alluvial soil. Calcium utilized by sandy soil grapevines was less than half thatutilized by those of alluvial soil. The seasonal absorption pattern of Ca was comparable for both soils.Results suggest that that seasonal uptake and partitioning of mineral nutrients are affected by soil typeand grapevine vigour.

The influence of phylogeny and ecology on root, shoot and plant ionomes of 14 native Brazilian species.

The ionome is the elemental composition of a living organism, its tissues, cells or cell compartments. The ionomes of roots, stems and leaves of 14 native Brazilian forest species were characterised to examine the relationships between plant and organ ionomes and the phylogenetic and ecological affiliations of species. The null hypothesis that ionomes of Brazilian forest species and their organs do not differ was tested. Concentrations of mineral nutrients in roots, stems and leaves were determined for 14 Brazilian forest species, representing seven angiosperm orders, grown hydroponically in a complete nutrient solution. The 14 species could be differentiated by their ionomes and the partitioning of mineral nutrients between organs. The ionomic differences between the 14 species did not reflect their phylogenetic relationships or successional ecology. Differences between shoot ionomes and root ionomes were greater than differences in the ionome of an organ when compared among genotypes. In conclusion, differences in ionomes of species and their organs reflect a combination of ancient phylogenetic and recent environmental adaptations.

Applications of Abscisic Acid and Increasing Concentrations of Calcium Affect the Partitioning of Mineral Nutrients between Tomato Leaf and Fruit Tissue

This study examined how abscisic acid (ABA) and calcium (Ca) concentrations in nutrient solution affect concentrations of mineral nutrients in tomato leaves and fruit. Tomato plants were grown in a greenhouse at 25/20 °C (day/night) under a 16 h photoperiod. Plants were treated with different concentrations of ABA and Ca. Calcium was applied via the irrigation lines at 60, 90, or 180 mg·L−1. ABA was applied as a combination of foliar sprays and root applications. For foliar ABA applications, treatments consisted of deionized (DI) water control (0.0 mg·L−1 ABA) or 500 mg·L−1 ABA. For ABA root applications, treatments consisted of no ABA control (0.0 mg·L−1 ABA) or 50 mg·L−1 ABA applied via the irrigation lines. Results indicate that mineral nutrient concentrations in tomato leaf and fruit tissue varied in connection with each exogenous application of ABA. Variability in mineral nutrient concentration depended on if ABA was applied to the leaf or root tissue. Additionally, increasing Ca treatment concentrations either decreased or did not change mineral nutrients in tomato and fruit tissue. Thus, tomato plants react to acquiring mineral nutrients in numerous mechanisms and, depending on how the applications of exogenous ABA are applied, can have varying effects on these mechanisms.

Interplay between chemistry and morphology in medical cannabis (Cannabis sativa L.)

Despite the long history of cannabis use, the chemical and physiological state of the plants have not sufficiently been addressed due to legal restrictions. Hundreds of secondary metabolites of therapeutic potential were identified in cannabis. This large number, together with the need to standardize chemical composition of the plant material supplied to patients dictates a need to understand interrelations between morphology and chemistry. The present study investigated the interplay between chemical profiles (of cannabinoids and the ionome) and locales in the plant body. We studied location and organ-specific effects on chemical profiles of cannabinoids, the ionome and physiological traits. A number of important morphological-related chemical trends were identified, which demonstrate in-planta variation in regulation of the chemotype: The cannabinoid profile changes with location along the plant demonstrating significant variation among differing heights for almost every cannabinoid studied. The content of most cannabinoids (including THC, CBD, CBG, CBC, THCV) substantially increased with plant height, both in the flowers and the inflorescence leaves. The concentration of cannabinoids in the inflorescence leaves is considerable and for THC and CBD reached about half of that found in flowers. Concentration in fan leaves is about 1/10 the concentration found in flowers. A number of cannabinoids, including CBC and CBG, were present in the inflorescence leaves at equal or greater levels than in the flowers. The partitioning of mineral nutrients between plant organs demonstrate typical uptake and translocation in the plant. The lower concentrations of N, P, K and higher concentration of Ca in fan-leaves compared with inflorescence-leaves, a result of in-planta translocation abilities in the phloem, supports the physiological findings that the fan leaves are older than the inflorescence leaves. The substantial spatial gradients in secondary-metabolites demonstrate organ and location-specific regulation of accumulation. This in-planta variability in regulation of the chemotype requires standardization for the development of Cannabis as a therapeutic crop for modern medicine.

Source-Sink Partitioning of Mineral Nutrients and Photo-assimilates in Tomato Plants Grown under Suboptimal Nutrition

A huge number of greenhouse soils in Korea have accumulated mineral elements which induce many nutritional and pathological problems. The present study was performed to the effects of the reduced fertilization on plant growth, and uptake and partitioning of minerals (N, P, K) and soluble carbohydrates using highly minerals-accumulated farmer's greenhouse soil. On the basis of the recommended application for tomato crop, the application rates of N, P and K were 110(50%)-5.2(5%)-41.5(35%)kg <TEX>$ha^{-1}$</TEX>, respectively, using Hoagland's nutrient solution. Tomato growth rates during the whole experiment were not significant between treatments, but it was found that a decrease in daily growth represented after 60 days of treatment (DAT). The reduced application led to a drastic decrease in the concentration of N, P and K in fruits, and, thus, this resulted in lower uptake after 40 DAT. The lower phloem export and utilization of soluble carbohydrates caused an accumulation of extra-carbohydrates in leaves, stems and fruits in the reduced application. The reduced fertilization induced the capture of N, P and K in leaves and of soluble carbohydrates in stems compared to the conventional application. In this study, we suggest that it is possible to delay the first fertigation time in minerals-accumulated soils without an adverse impact on crop growth, but it is necessary to regularly monitor mineral status in soil to ensure a balanced uptake, synthesis and partitioning of minerals and carbohydrates.

Multiple impacts of the plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2 on nutrient and ABA relations of Pisum sativum.

Resolving the physiological mechanisms by which rhizobacteria enhance plant growth is difficult, since many such bacteria contain multiple plant growth-promoting properties. To understand further how the 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCd)-containing rhizobacterium Variovorax paradoxus 5C-2 affects plant growth, the flows and partitioning of mineral nutrients and abscisic acid (ABA) and ABA metabolism were studied in pea (Pisum sativum) plants following rhizosphere bacterial inoculation. Although root architecture was not affected, inoculation increased root and shoot biomass, and stomatal conductance, by 20, 15, and 24%, respectively, and increased N, P, K, Ca, and Mg uptake by 16, 81, 50, 46, and 58%, respectively. P deposition in inoculated plant roots was 4.9 times higher than that in uninoculated controls. Rhizobacterial inoculation increased root to shoot xylem flows and shoot to root phloem flows of K by 1.8- and 2.1-fold, respectively. In control plants, major sinks for K deposition were the roots and upper shoot (43% and 49% of total uptake, respectively), while rhizobacterial inoculation increased K distribution to the lower shoot at the expense of other compartments (xylem, phloem, and upper shoot). Despite being unable to metabolize ABA in vitro, V. paradoxus 5C-2 decreased root ABA concentrations and accumulation by 40–60%. Although inoculation decreased xylem ABA flows, phloem ABA flows increased. Whether bacterial ACCd attenuates root to shoot ABA signalling requires further investigation, since ABA is critical to maintain growth of droughted plants, and ACCd-containing organisms have been advocated as a means of minimizing growth inhibition of plants in drying soil.

A Minimal Cysteine Motif Required to Activate the SKOR K+ Channel of Arabidopsis by the Reactive Oxygen Species H2O2*[S

Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca(2+) and K(+) channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K(+) channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H(2)O(2). We show that H(2)O(2) rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H(2)O(2) and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H(2)O(2)-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys(168) located within the S3 α-helix of the voltage sensor complex, to be essential for sensitivity to H(2)O(2). The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys(168) as a critical target for H(2)O(2), and implicate ROS-mediated control of the K(+) channel in regulating mineral nutrient partitioning within the plant.

Nutritional relationships between hemi-parasitic mistletoe and some of its deciduous hosts in different habitats

Parasitism of plants by other plants provides an exceptional opportunity for investigating correlative nutritional relationships. Because of lacking a usual plant-root sytem capable of active uptake, the best correlation for predicting the concentrations of elements in parasitic plants is often those in the host plants. This study, therefore, mainly focuses on determination of i) mineral nutrient partitioning between hemi-parasitic white berry mistletoe (Viscum album L. subsp. album) and four of its deciduous hosts growing in different habitats namely wetland and semi-arid and ii) effects of these habitat types on nutrient absorption. During the research, leaf samples of both hemi-parasites and their host plants were chemically analysed, mistletoes on each host plants were counted and the results were considered statistically. Concentrations of some elements (N, P, K, Na, S, Cu, Zn) were higher in mistletoe whereas some others (Ca, Mg, Fe, Mn and B) were higher in the hosts (p< 0.05). Habitat type was also determined to be effective in host-parasite systems. Revealing information about nutritional interactions between multi-host hemi-parasites and their host plants is a useful tool to understand their functions in ecosystems, population-community dynamics and their co-evolution process.

Mineral nutrient status, some quality and morphological characteristics changes in peanut (Arachis hypogaea L.) cultivars under salt stress.

Peanut ( Arachis hypogaea L.) is considered to be one of the most important crops which thrive in newly reclaimed sandy soils as a leguminous crop of high nutritive value and a source of edible oil. Our study tested the effects of different salt levels on mineral nutrient partitioning (Na + , K + , Mg 2+ , Ca 2+ , P and N) and some quality (dry weight and leaf relative water content) and morphological (plant height, number of leaves) characteristics of peanut commercial cultivars. Four peanut cultivars (Mbiah, Ngondo, Pyrieur and Vanda) were used in this experiment. Three concentrations of salt solution including 50, 100 and 200 mM NaCl and the control (Wacquant nutrient solution) were used in irrigation. The pot experiment was arranged in completely randomized design with four replicates. The leaf relative water content (LRWC) provoked by the salinity in nutrient solution decreased from 85.08 to 83.43%, 87.82 to 85.30%, 85.81 to 78.20% and 85.90 to 79.70% in Mbiah, Ngondo, Pyrieur and Vanda cultivars respectively. The results showed that the salt stress reduced significantly (p 0.05) reduced under salt stress in Ngondo plant organs except at high salt-treated (200 mM NaCl). The Ngondo cultivar was observed to have relatively higher tolerance on average of all growth parameters and mineral nutrient status than others. This finding suggested that the Ngondo cultivar could be used to highlight the newly salt cultivated sandy soils in arid, semi-arid regions and similar environments across Cameroon. Key words: Arachis hypogaea , growth parameters, mineral nutrient, plant organs, salt stress.

Solute flows from Hordeum vulgare to the hemiparasite Rhinanthus minor and the influence of infection on host and parasite nutrient relations.

Using the facultative root hemiparasite Rhinanthus minor and Hordeum vulgare L. as a host, the flows and partitioning of mineral nutrients within the host, the parasite and between host and parasite have been studied during the study period 41-54 d after planting, i.e approximately 30-43 d after successful attachment of the parasite to the host. In parasitising Rhinanthus shoot growth was 12-fold, but root growth only 2-fold increased compared to non-parasitising plants. Conversely, in the Hordeum host, shoot dry matter growth was clearly reduced, by 33% in leaf laminae and by 52% in leaf sheaths, whereas root growth was only slightly reduced as a consequence of parasitism. Growth-dependent increments of total nitrogen (N) and phosphorus (P) and of potassium (K), calcium (Ca) and magnesium (Mg) in parasitising Rhinanthus shoot were strongly increased, particularly increments of total N and P, which were 18 and 42 times, respectively, higher than in solitary Rhinanthus. However, increments of the above mineral nutrients in leaf sheaths of parasitised Hordeum vulgare were more strongly decreased than in leaf laminae in response to parasitic attack. Estimation of the flows of nutrients revealed that Rhinanthus withdrew from the host xylem sap about the same percentage of each nutrients: 18% of total N, 22% of P and 20% of K. Within the host almost all net flows of nutrient ions were decreased due to parasitism, but retranslocation from shoot to root was somewhat increased for all nutrients. Quantitative information is provided to show that the substantially increased growth in the shoot of attached Rhinanthus and the observed decrease in Hordeum shoot growth after infection were related to strongly elevated supply of nitrogen and phosphorus in the parasite and to incipient deficiency of these nutrients in the parasitised host. The flows of nutrients between host and parasite are discussed in terms of low selectivity of nutrient abstraction from the host xylem by the hemiparasite Rhinanthus minor.

Biomass and mineral nutrient partitioning in a developing tamarillo ( Cyphomandra betacea) crop

The accumulation of dry matter (DM) plus macro- and micronutrients by various components of developing tamarillo ( Cyphomandra betacea (Cav.) Sendt. cv. ‘Oratia Red’) plants was recorded over a 3-year period covering growth from seedlings to a mature commercial crop. Five plants were harvested every 2 months and separated into perennial components (tap root, roots, stem wood, stem bark, and wood and bark from year-old branches) and current season’s growth (fruiting laterals, leaves, flowers and fruit) for determination of DM and mineral composition. DM accumulation in the perennial framework conformed to a sigmoidal pattern of increase over the entire trial period. In contrast, DM accumulation by annual components was greatest in the 4–6 months after pruning each season, and reflected the indeterminant pattern of vegetative growth, flowering and fruit set associated with this crop. Nutrient concentrations in dissected components were generally constant. Consequently, accumulation of DM and individual nutrients was strongly correlated. Potassium and nitrogen were the elements acquired in greatest amounts by tamarillo plants in each season. During Year 3, the amount of N, P and K accumulated amounted to 109 kg N ha −1, 11 kg P ha −1 and 145 kg K ha −1 of which 39, 27 and 48% was removed in harvested fruit, respectively. Nutrient accumulation budgets identified the 4–6 months immediately after pruning as the time when exogenous nutrients were acquired in greatest amount, and nutrient reserves in the perennial framework were withdrawn to sustain any shortfall in uptake. Adequate nutrition of commercial crops will depend on application of fertiliser nutrients timed to meet these requirements.

WATER RELATIONS, CALCIUM AND POTASSIUM CONCENTRATION IN FRUITS AND LEAVES DURING ANNUAL GROWTH IN MATURE KIWIFRUIT PLANTS

WATER RELATIONS, CALCIUM AND POTASSIUM CONCENTRATION IN FRUITS AND LEAVES DURING ANNUAL GROWTH IN MATURE KIWIFRUIT PLANTS

Accumulation and partitioning of mineral nutrients in wheat as influenced by nitrogen form

The form of nitrogen (N) [e.g., nitrate (NC3 ‐) and ammonium (NH4 +)] available to plants affects many growth processes, including mineral nutrient acquisition. The objective of this study was to assess the effects of N form on the accumulation and partitioning of mineral nutrients in wheat. Two species of spring wheat (Triticum aestivum L. cv. Len and Triticum durum Desf. cv. Inbar) were grown hydroponically in the greenhouse with N supplied as either all NO3 ‐, or all NH4 +, or an equal mixture of the two forms (mixed N). Plants were harvested after 21 days of growth, divided into shoots and roots and each part analyzed for nine mineral elements [phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and boron (B)]. The accumulation and partitioning of the mineral nutrients was dependent on the wheat species, the N form, and the nature of the ion. Inbar plants always accumulated more of each element than did Len. Compared with all NO3 ‐ nutrition, mixed N increased the whole plant and/or shoot accumulation of P, K, Cu, and B, but not Ca, Mg, Fe, Mn, and Zn; while all NH4 + decreased these values for most elements. With few exceptions, N form did not affect either the accumulation or partitioning of Mg and Fe. Plants grown with all NO3 ‐ accumulated more Mn and Zn than those receiving mixed N or all NH4 +, while the partitioning of both ions was not affected by N form. When grown with mixed N or all NH4 +, less P, K, Cu, and B was partitioned to the roots compared to plants receiving all NO3 ‐. These results demonstrate the differential effects of N form on mineral nutrient acquisition and nutrient use by wheat, which may be related to N‐form induced differences in plant growth.

Harvest index: a review of its use in plant breeding and crop physiology

SummaryThis review charts the use of the concept of harvest index in crop improvement and physiology, concentrating on the literature from the last 20 years. Evidence from abstract journals indicates that the term has been applied most to small grain cereal crops and pulses, in India, Western Europe and the USA, and that it has been less useful for maize and tuber crops. Standard methods of measuring harvest index, the associated problems of measurement and interpretation, and representative values for a range of world species are reviewed. The values for modern varieties of most intensively‐cultivated grain crops fall within the range 0.4 to 0.6. Variation between varieties of the same species is illustrated by trends in the harvest indices of old, outclassed and recent varieties of temperate and mediterranean wheat and barley (compared under uniform conditions); this shows a progressive increase throughout the present century, although improvement has been much slower in Australia and Canada than in the UK. In most cases, the improvement in harvest index has been a consequence of increased grain population density coupled with stable individual grain weight. The high heritability of harvest index is explored by examining its (rather weak) response to variation in environmental factors (fertilisation, population density, application of growth regulators) in the absence of severe stress. A fuller perspective is gained by reviewing aspects of the harvest index of rice, maize and tropical pulses. With rice, attention must be paid to the fact that the adhering lemma and palea (not primarily part of economic yield) can make up 20% of grain weight; and there are important interactions among biomass, grain yield and season length. Maize differs from most small grain crops in that harvest index (in N. American varieties) was already high at the start of this century, and increases in yield potential have been largely the consequence of increased biomass production. The harvest index of many pulse species and varieties tends to be low because selection has been for some yield in all seasons. Extension of the harvest index concept to express the partitioning of mineral nutrients as well as dry matter (e.g. the nitrogen harvest index) has provided a range of responses whose implications for production and breeding remain to be explored. It is concluded that even though the principal cereal crops appear to be approaching the upper limit of harvest index, and future yield gains will have to be sought by increased biomass production, there will still be a need for the concept of harvest index as a tool in interpreting crop response to different environments and climatic change.

Etiolated Growth as Measure of Non-structural Biomass in Lucerne Taproots

Enzymatic hydrolysis of starch in lucerne (Medicago sativa L.) taproots is the conventional method used to determine the quantity of carbohydrates allocated to regrowth. Etiolated growth from a taproot could be used to quantify total root biomass allocated to regrowth. This study compared concentrations of non-structural carbohydrates, as measured by α-amylase hydrolysis of starch to glucose, to concentrations of non-structural biomass, as measured by etiolated growth from lucerne taproots placed in an incubator and plants in situ. The concentration of starch from enzymatically assayed taproots was 325 g kg-1 expressed as glucose equivalents. Etiolated growth and weight loss by respiration from plants grown in the incubator accounted for 524 g of actual biomass per kg of root. There was 46·2 g kg-1 of N, 3·1 of P, and 33·1 of K in the etiolated growth. An 88% increase in etiolated growth dry weight was observed from plants in situ compared to taproots placed in the incubator. Accurate quantification on non-structural biomass should not be limited to sampling just the taproot, but must included the entire root system. Compared to determining non-structural carbohydrates by enzymatic hydrolysis of starch, the procedure used in determining non-structural biomass by etiolate growth gave results in units relative to the plant. The use of etiolate growth also provided information on mineral nutrient partitioning from root to shoots, was less technically demanding, and could be applied to the entire root system.

Seasonal Dynamics of Biomass and Mineral Nutrient Partitioning in Mature Kiwifruit Vines

The accumulation of dry matter plus macro- and micronutrients by various components of 6-year-old, field-grown kiwifruit vines (Actinidia deliciosa var. deliciosa cv. Hayward) was recorded over one season. Twenty vines were harvested periodically throughout the year and separated into perennial components (roots<20 mm diameter, structural roots, stump, stem, cordon, one-year-old fruiting wood) and current season's growth (non-fruiting shoots, laterals on fruiting wood, leaves and fruit). There was minimal seasonal variation (CVs<7%) in biomass change in perennial components of the vine

Biomass and mineral nutrient partitioning in relation to seasonal growth of Zantedeschia

Dry matter, mineral composition and nutrient contents were measured in component tissues of Zantedeschia elliottiana harvested from a commercial planting at frequent intervals throughout a 7 month growing cycle. The growth cycle was characterised by three distinct phases. During the first phase (5–7 weeks growth), roots and vegetative tissues developed concurrently, tuber dry weights declined to 50% of their starting mass and flowering was completed. In the second phase (about 6–16 weeks after planting), there was rapid growth and maximum nutrient uptake — the dry weight and number of leaves increased to their maximum, new tuberous tissue formed and root growth declined. The final phase was initiated with shoot senescence (16 weeks growth). Tuber dry weights slowly declined in the absence of vegetation and with the onset of dormancy. Seasonal changes in the concentration and content of macro- and micronutrients in roots, tubers, blades, petioles and flowers are described. Between 20 and 56% of the nutrient stored in tubers was removed to support new season's growth in the 5–7 weeks following planting. By contrast, there was minimal remobilisation of Ca, Mn or Na from tubers. Nitrogen and K were the elements required in the greatest amount by Zantedeschia. These results are discussed in terms of fertiliser programmes for commercial production of this crop.