Changes In Dry Matter Partitioning Research Articles

Influence of Water Deficit on Photosynthetic Activity, Dry Matter Partitioning and Grain Yield of Different Durum and Bread Wheat Genotypes

We aimed to study the influence of soil water deficit on gas exchange parameters, dry matter partitioning in leaves, stem and spike and grain yield of durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes in the 2013–2014 and 2014–2015 growing seasons. Water stress caused reduction of stomatal conductance, photosynthesis rate, transpiration rate, an increase of intercellular CO2 concentration. Photosynthesis rate positively correlated with growth rate of genotypes. Drought stress caused adaptive changes in dry matter partitioning between leaves, stem and spike of wheat genotypes. Stem dry mass increased until kernel ripening. Drought stress accelerated dry mass reduction in leaves and stem. High growth rate of spike dry mass was revealed in genotypes with late heading time. Spike dry mass positively correlated with photosynthesis rate and grain yield. Generally, bread wheat is more productive and tolerant to drought stress than durum wheat.

Rootstocks can enhance tomato growth and quality characteristics at low potassium supply

Grafting is nowadays regarded as a rapid tool aimed at increasing environmental stress tolerance of fruit vegetables. In cultivation systems oversupply of cations, saline or drought conditions and the type of the growing system can easily cause potassium (K+) deficiency and thus, lead to a damage of physiological processes. The hypothesis was raised that rootstocks alleviate stress symptoms of tomato at moderate deficient K+ supply (4mM) compared with regular (8mM) in the nutrient solution. Moreover, the long-term response of grafted plants (‘Classy’, ‘Piccolino’) was studied to quantify the effectiveness of rootstocks (‘Maxifort’ and ‘Brigeor’) in mitigating K+ stress particularly on tomato yield and fruit quality attributes, such as appearance, firmness, taste and health promoting compounds. K+ deficiency resulted in a reduction of root growth, yield, fruit appearance, and carotenoids. On the other hand, firmness and concentration on single and total fruit sugars increased. In most of the characteristics negatively affected by low K+ supply, grafting was able to alleviate these effects. Thus, rootstocks improved root growth and morphology, yield, concentration of carotenoids and also titratable acids in fruits especially at low K+ supply. The portion of blossom end rot was reduced. However, the alleviation depended on the rootstock scion combination. Possible reasons of the rootstock effects were discussed, such as change in dry matter partitioning in favour of the fruits, improved Ca2+ availability and transport, increased photosynthesis and associated relationship between sugar and synthesis of ascorbic acid and carotenoids.

Recovery dynamics of rainfed winter wheat after livestock grazing 2. Light interception, radiation-use efficiency and dry-matter partitioning

Grazing of cereal crops reduces canopy light interception and could potentially reduce biomass production and grain yields. Alternatively, defoliation after canopy closure may increase light penetration and enhance radiation-use efficiency (RUE, shoot dry matter produced per unit light intercepted). Changes in dry matter partitioning following grazing may also ameliorate grain yield penalties. Experiments with rainfed winter wheat were conducted near Canberra, Australia, to investigate the effect of different intensity or duration of grazing on two cultivars. Grazing reduced leaf area index (LAI), light interception and growth rates by up to 90% but did not affect overall RUE. Although grazing caused significant reductions in cumulative light interception and total dry matter accumulation, it did not affect grain yields because grazed crops had delayed phenological development, allowing increased partitioning of shoot dry matter to spikes. Grazing reduced stem dry matter accumulation and consequently decreased the amount of stem assimilate available for retranslocation to kernels by up to 75%. However, by delaying crop ontogeny, grazing prolonged green area duration after anthesis and thereby increased the supply of assimilates from current photosynthesis to developing kernels, mitigating potential yield penalties caused by defoliation.

Mild salinity improves sugar beet (Beta vulgaris L.) quality

Sugar beet (Beta vulgaris L.) is cultivated mainly on saline soils. Low levels of salinity stimulate growth of this crop plant possibly due to production of broader leaves as sources of assimilates. In this work, six cultivars were studied under mild salinity (EC = 5.5 dS m−1) in a field experiment to analyse its effect on growth parameters and yield of storage root and sugar accumulation. An attempt was also made to determine the contributing role of photosynthetic gas exchange in response of sugar beet plants to salinity. Production of greater leaf area in salinized plants occurred only transitionally in the early growth period; in progression of the growing season it was decreased, and at 3rd harvest (100 days after treatment) it was significantly lower compared with control plants without cultivar differences. Leaf chlorophyll fluorescence, net photosynthesis rate, and stomatal conductance did not change by salinity significantly. Although, at the end of growth season, leaf area and potential photosynthesizing component of salinized plants on the basis of leaf area (LAR) or weight (LWR) were significantly lower than for control plants, weight of storage root and sugar content were up to 90 and 37% higher than in control plants, respectively. Consequently, a considerable higher yield under mild salinity conditions in sugar beet is not attributable to higher leaf area or, therefore, higher photosynthetic capacity of whole plants. Indeed, the storage roots benefit from lower dry matter and surface production of shoot during the late growing season (because of lower nitrogen assimilation and a slight drought stress of salinized plants) and a change in dry-matter partitioning in favor of roots takes place. However, a possible special effect of Na on carbon allocation for storage and structure and involvement of growth regulators in the change of root-shoot allometry could not be excluded.

Seasonal Changes in Dry Matter Partitioning, Yield, and Crude Protein of Intermediate Wheatgrass and Smooth Bromegrass

Seasonal patterns of dry matter partitioning and nutritive value of leaf and stem components of grass species is important for selecting species for planting, planning grazing strategies, and making management decisions. Our objective was to compare dry matter yield and crude protein (CP) yield of blade, sheath, and stem fractions of intermediate wheatgrass [Elytrigia intermedia (Host) Nevski] and smooth bromegrass (Bromus inermis Leyss.) during the growing season. Intermediate wheatgrass and smooth bromegrass were sampled on a weekly basis from 14 May to 25 June in 1997 and from 5 May to 23 June in 1998 at Lincoln, NE. Samples were separated into blade, sheath, stem, and inflorescence components and yield and concentration of CP were determined. Smooth bromegrass tended to have greater blade and stem yield than intermediate wheatgrass during the 1997 and 1998 sampling periods. Yield of sheath was similar between species. Crude protein yield of blade and stem was also greater for smooth bromegrass than intermediate wheatgrass in both years. Sheath CP yield was greater for intermediate wheatgrass in 1998. Both species followed a similar pattern of dry matter accumulation; however, intermediate wheatgrass dry matter accumulation, especially stem, tended to be 1 to 2 wk behind smooth bromegrass. Differences in dry matter partitioning, yield, and CP in these two species illustrates the advantages having a complement of forage species. Choosing a diversity of species with differing growth habits would be beneficial for improving the distribution of forage yield and quality to match the seasonal demand of grazing livestock.

Sugarcane water stress criteria for irrigation and drying off

In Australia about 60% of sugar produced from sugarcane depends to some extent on irrigation. Regional water supplies are often limited and the pressure on irrigators to defend or improve their farming practices can be quite severe. Compared to other crops, little is known about how far water can be stretched in sugarcane without affecting sugar yield. In particular, there is little information on the response of important yield forming processes to soil water deficits. Two experiments were designed to follow the effect of increasing soil water deficit (SWD) on processes such as leaf appearance, leaf and stalk extension, leaf area development, biomass and sucrose accumulation and dry matter partitioning. The first experiment was designed to coincide with a period of high evaporative demand and the second experiment with a period of low evaporative demand. As SWD increased in the first experiment reductions occurred first in leaf and stalk extension rate, then in green leaves per stalk, then in biomass accumulation and finally in sucrose accumulation. The data indicated that irrigation can be used more sparingly since biomass accumulation (hence net photosynthesis) can tolerate greater deficits than previously recognized. Water stress resulted in marked changes in dry matter partitioning. In the second experiment sucrose yield was increased at one point to more than 3 t/ha over the yield of the control treatment. Dry matter was diverted from tops (green leaves and immature stem) and from stalk fibre to make up the additional sucrose yield. Simple crop measurements (leaf or stalk extension, green leaf number) are suggested as indicators of when to irrigate to avoid reductions in biomass accumulation or when to harvest in order to benefit most from changes in dry matter partitioning due to water stress. Suggestions are also made for improving process level growth models of sugarcane.

Cotton Growth and Physiological Responses to Boron Deficiency

Boron (B) deficiency is common in some cotton (Gossypium hirsutum L.) growing regions of the world. A better understanding of changes in the growth and physiological characteristics of cotton plants during the development of B deficiency will help us to define field diagnosis techniques and improve B fertilizer management recommendation. An experiment was conducted in a controlled‐environment growth chamber to determine effects of B deficiency during early vegetative growth on leaf photosynthesis, plant dry matter accumulation, photosynthetic assimilate partitioning, and other physiological parameters. Boron deficiency considerably decreased leaf net photosynthetic rate, plant height, leaf area, fruiting sites, and dry matter accumulation during squaring and fruiting. Depressed photosynthesis and plant growth (especially fruits and roots) resulted in increased fruit abscission and changes in dry matter partitioning among plant tissues. The results help explain effects of B deficiency on suppression of cotton growth and yield and provide information for improving the diagnosis of B deficiency in cotton production.

Characterisation and microbial utilisation of exudate material from the rhizosphere of Lolium perenne grown under CO 2 enrichment

The effects of elevated atmospheric CO 2 concentration on alterations, both qualitatively and quantitatively, of exuded compounds from the roots of Lolium perenne seedlings were investigated by growing plants in a sterilised sand microcosm unit. In addition, the effect of CO 2 treatment on carbon substrate utilisation of microbial populations extracted from the rhizosphere of L. perenne seedlings grown in soil microcosm units was examined and alterations on microbial activity and diversity assessed using a commercially-available redox-based sole C source utilisation test (Biolog®) including additional exudate compounds. Both types of microcosm units (sand and soil) were maintained at specific growth conditions under two CO 2 regimes (450 and 720 μmol mol −1). Growth of L. perenne seedlings from both types of microcosm units was enhanced under elevated atmospheric CO 2 although the root-to-shoot ratios were not significantly altered, indicating no gross change in dry matter partitioning. Cumulative total organic carbon (TOC) release in the exudate material over the duration of the experiment was significantly ( P≤0.05) higher from ambient-grown seedlings despite a significant ( P≤0.05) increase in the dry weight of roots of the elevated CO 2 grown seedlings as determined at harvest. Over the individual sampling periods TOC release was significantly ( P≤0.05) higher from elevated CO 2 grown seedlings on only one occasion (21 d). Qualitative differences, measured between d 1–6 and 14–18, also occurred with elevated CO 2 treatment decreasing the amount of phenolic acids and total sugars at the latter sampling period compared to ambient CO 2 seedlings. Total numbers of bacteria were significantly ( P≤0.05) decreased under elevated CO 2 although culturable numbers significantly ( P≤0.05) increased. This increase in culturable microorganisms may explain the faster carbon source utilisation rates of the elevated CO 2 treatment. No change in morphotypes of microbial colonies were observed suggesting a quantitative difference due to elevated CO 2 treatment only.

Influence of Crop Load on Photosynthesis and Dry Matter Partitioning of Seyval Grapevines. III. Seasonal Changes in Dry Matter Partitioning, Vine Morphology, Yield, and Fruit Composition

Single leaf photosynthesis, whole vine photosynthesis measured in a whole plant chamber, dry matter partitioning, and several morphological indices were measured at four phenological stages of development on two-year-old, own-rooted Seyval grapevines adjusted to five different crop loads. Crop loads were 0, 1, 2, 4, or 6 clusters/vine with all laterals removed to eliminate intra-vine shading. Leaf area was inversely related to crop load, with differences evident as early as fruit set. Differences in dry weight partitioning did not become evident until mid-season. Leaf and shoot dry weight were inversely correlated, and fruit dry weight positively correlated with crop load, respectively. Root dry weight was inversely related to crop load only at harvest. Leaf area per vine, leaf size, shoot length, node number, and internode length were inversely related to crop load. Berries per cluster and cluster weight were inversely correlated with clusters per vine. Yield and berries per vine were correlated with clusters per vine. Sugar accumulation and shoot maturation were delayed by high crop loads. Implications of the crop load treatments on vine photosynthesis are discussed.

Analysis of Dry Matter Partitioning in Dactylis glomerata during Vegetative Growth Using a Carbon Budget Model

The dry matter partitioning in vegetative plants of Dactylis glomerata was studied from experiments performed in controlled environments. Plants were grown hydroponically in growth chambers, at two constant temperatures (17 and 25 °C). In both experiments the root fraction decreased regularly with time, an effect that was more accentuated in the higher temperature regime. In order to explain the change in dry matter partitioning, the experimental shoot and root growth were analysed using a carbon budget model which includes shoot and root maintenance requirements. The model predicts a relationship between the root specific growth rate and the product of shoot specific growth rate and shoot to root dry weight ratio. In the range of experimental accuracy, this relationship was found to be linear at both temperatures, which should indicate that the partitioning coefficients and the root maintenance coefficient remained constant during vegetative growth. The effect of temperature on the value of these coefficients can be specified from a linear regression analysis. Between 17 and 25 °C, the root maintenance coefficient increased by about a factor of two, whereas the partitioning coefficients did not vary significantly. On the basis of these results, it was shown that the decrease in root fraction during vegetative growth should be mainly attributed to the decrease in net specific activity of shoots.

Retranslocation of carbon reserves from the woody storage tissues into the fruit as a response to defoliation stress during the ripening period in Vitis vinifera L.

A technique for reliable labeling of the carbon reserves of the trunk and roots without labeling the current year's growth of grapevines was developed in order to study retranslocation of carbon from the perennial storage tissues into the fruit in response to defoliation stress during the ripening period. A special training system with two shoots was used: the lower one (feeding shoot) was cut back and defoliated to one single leaf (14CO2-feeding leaf) while the other (main shoot) was topped to 12 leaves. The potted plants were placed in a water bath at 30 °C to increase root temperature and therefore their sink activity. Additionally, a cold barrier (2–4 °C) was installed at the base of the main shoot to inhibit acropetal 14C translocation. Using this method, we were able to direct labeled assimilates to trunk and roots in preference to the current year's growth. On vines with root and shoot at ambient temperature, 44% of the 14C activity was found in the main shoot 16 h after feeding whereas only 2% was found in the temperature-treated vines. At the onset of fruit ripening, and at three-week intervals thereafter until harvest, potted grapevines were fed with 14CO2 using the temperature treatment described above. Sixteen hours after feeding, half of the vines of each group were defoliated by removing all except the two uppermost main leaves. Three weeks after each treatment, vines were destructively harvested and the dry weight and 14C incorporation determined for all plant parts. Under non-stressing conditions, there was no retranslocation of carbon reserves to support fruit maturation. Vines responded to defoliation stress by altering the natural translocation pattern and directing carbon stored in the lower parts to the fruit. In the three weeks following veraison (the inception of ripening in the grape berry), 12% of the labeled carbon reserves was translocated to the fruit of defoliated plants compared to 1.6% found in the clusters of control vines. Retranslocation from trunk and roots was highest during the middle of the ripening period, when 32% of the labeled carbon was found in the fruit compared to 0.7% in control plants. Defoliation during this period also caused major changes in dry-matter partitioning: the fruit represented 31% of total plant biomass compared to 21% measured in the control vines. Root growth was reduced by defoliation at veraison and during the ripening period. Defoliation three weeks before harvest did not affect dry matter or 14C partitioning.

PHYSIOLOGICAL CHARACTERISTICS OF THREE GROWTH TYPES

The objective was to study selected physiological characteristics of the canopy and examine changes in dry matter partitioning between the root and shoot in two genetically reduced size growth types (dwarf and pillar) relative to the standard growth type. The dwarf phenotype had reduced leaf/root ratio, less allocation of dry matter to woody tissue and more to leaf tissue, high net photosynthesis, and lower leaf respiration compared to the standard and pillar phenotypes. The dwarf and pillar types had greater resistance to water flow than the standard type. Genetic changes in growth habit significantly alter many physiological parameters of peach tree growth and structure.

Effects of light intensity and light quality on the obligate shade plantAglaonema commutatum.II. Photosynthesis and dry-matter partitioning

The introduction of Aglaonema commutatum as an ornamental plant has been an empirical process. The success reached seems due to the capacity of the species to grow in very low light intensities for long periods. The results obtained have shown: (1) the light- saturated photosynthetic rate was very low even for shade plants (0.7-1.0 (μmol m-2s-1), (2) growth at the lowest irradiance did not stop despite a negative net CO2 exchange. The growth of new leaves was sustained by reserves stored in the cutting, (3) the plants grown at the lowest irradiances showed a decrease in light-saturated photosynthetic rate and a change in dry-matter partitioning with poor growth of root systems, and (4) the responses were influenced more by light intensity than by light quality.

Potential for Increasing Cotton Yields Through Enhanced Partitioning to Reproductive Structures

Yield increases in cotton (Gossypium hirsutum L.) have been primarily through changes in partitioning dry matter from vegetative to reproductive structures. The objective of this study was to determine if yield increases would likely continue through continued changes in dry matter partitioning. Five obsolete cultivars, five popular and high yielding cultivars from five cotton breeding organizations, and 15 advanced strains from five cotton breeding organizations were used for yield and growth analyses at three environments, two in 1985 and one in 1986. Obsolete cultivars averaged 24% less lint than the 20 more modern genotypes and showed greater investment of dry matter into vegetative rather than reproductive structures. There was no major difference in mean yield or growth characteristics detected between the five currently used cultivars and the 15 strains. However, these 20 genotypes showed significant (P < 0.05) genetic variability for yield and most growth characteristics. Plant height and stem wt. to total dry wt. ratio showed strong negative genetic correlations with yield (r = −0.44 to −0.80). Strong positive genetic associations with yield were found for boll wt. to total dry wt. ratio (r = 0.86) and the late sampling of reproductive‐vegetative ratio (r = 0.91). This study suggests that yield increases through the use of conventional breeding methods are likely to be achieved through continued partitioning of dry matter from vegetative to reproductive structures.

Morphology of Alfalfa Divergently Selected for Herbage Lignin Concentration

Programs to improve alfalfa (Medicago sativa L.) nutritive value have used selection criteria based on total herbage cell‐wall composition. There is only limited information addressing the effect of total‐herbage based phenotypic selection on changes in dry‐matter partitioning of the plant and on the nutritive value of plant parts. The objective of this study was to determine the effects of divergent herbage selection for alfalfa cell‐wall components on plant morphology. Two groups of germplasm were observed. Group 1 consisted of six syn‐2 lines derived from two‐parent combinations, which were randomly selected from ‘Saranac‐AR’ for high (HL) or low (LL) herbage acid‐detergent lignin concentration. Group 2 had HL and 13 LL lines that were full‐sib lines produced on pairs of parents from the Group 1 synthetics. Group 1 was grown for two harvests in a greenhouse and one harvest in the field, and Group 2 was grown for two harvests in the field. Compared with HL lines, LL lines had a greater leaf‐to‐stem ratio, especially in the fraction above the sixth node from the stem base. For LL lines, this ratio in the upper plant fraction was 53, 26, and 18% greater than HL lines for Group I greenhouse, Group 1 field, and Group 2, respectively. When harvested at the same time, LL lines were less mature than HL lines, and, for Group 2, main stem length of LL lines was about 30 mm shorter than HL lines. Dry‐matter yield of HL lines was 17, 28, and 28% greater than LL lines for Group 1 greenhouse, Group 1 field, and Group 2, respectively. Most of the differences between divergent types were related to changes above the sixth node. Thus, selection for improved nutritive value in total herbage of alfalfa may result in marked changes in plant morphology.

The assessment of net dry matter partitioning by stepwise multivariate analysis of variance

A serial procedure is described involving the analysis of variance, multivariate analysis of variance, and stepwise multivariate analysis of variance. The procedure identifies significant contributions by different plant components to changes in net dry matter partitioning induced by experimental treatments. The procedure was applied to results from a study of plants grown at different atmospheric CO2 concentrations. It confirmed that CO2 treatments caused significant changes in dry matter partitioning and that the set of plant components that best expressed the effects of CO2 treatments changed during plant growth.

Compensating Effects to Growth of Changes in Dry Matter Allocation in Response to Variation in Photosynthetic Characteristics Induced by Photoperiod, Light and Nitrogen

High N-nutrition, high light and long photoperiod increased photosynthetic capacity (Amax) per leaf area of Raphanus sativus × raphanistrum. The effect of Amax on growth was enhanced by an increased fraction of dry matter partitioned into the shoot, resulting in a larger canopy. Low N-nutrition, low light and a short photoperiod reversed these responses. At intermediate combinations, such as low light and long photoperiod or high light and short photoperiod, Amax and the actual net photosynthesis per leaf area (A) neither correlated with the carbon uptake rate of the canopy as a whole nor with whole plant growth. A compensatory effect to growth of changes in dry matter partitioning in response to variation in photosynthetic characteristics induced by light and N-nutrition is discussed in terms of two competitive feedbacks. For growth a long photoperiod compensated for low light or low N-nutrition. The results indicate that extrapolations from rates to gains are only valid under defined environmental conditions, especially when different photoperiods and effects on leaf ontogeny are involved.

Carbon Dioxide Enrichment Increases Yield of Valencia Orange

The response to elevated CO2 of 3-year-old fruiting Valencia orange scions (Citrus sinensis (L.) Osbeck) on citrange rootstock (C. sinensis × Poncirus trifoliata (L.) Raf.) was studied over a 12-month period under controlled environmental conditions. CO2 enrichment to approx. 800 �bar CO2 which com- menced just prior to anthesis shortened the period of fruitlet abscission. Trees enriched to 800 �bar CO2 retained 70% more fruit, which at harvest were not significantly smaller in diameter or lower in fresh weight than fruit from control trees grown at approx. 400 �bar CO2. Fruit from the CO2 enriched trees also did not differ from the controls in soluble solids content, dry weight, seed number or rind thickness. The progression of fruit coloration was more rapid for the CO2 enriched trees. Dry weight of leaves and branches from the scion portion of the trees and the roots and stem of the rootstock portion did not differ between treatments at time of harvest. Leaf areas were also similar. However, specific leaf dry weight was 25% greater for the CO2 enriched treatment. Changes in dry matter partitioning resulted from the greater fruit yield (58% increase in dry weight) with CO2 enrichment. Photosynthetic rates observed at intervals over the experimental period were always lower in the CO2 enriched treatment compared to controls when measured at the same partial pressure of CO2. However photosynthetic rates in the CO2 enriched cabinet were always higher because of the increased level of CO2. The extent of this difference between the treatments varied with fruit development and increased from 23% higher photosynthetic rates in the CO2 enriched chamber at the end of flowering to 77% higher rates when fruits were 5 cm in diameter and decreased to 18% higher rates when fruit coloration was well advanced. Flushes of leaves that developed during the experiment also showed similar photo- synthetic responses to CO2 enrichment and their photosynthetic rates declined as fruit matured. These results indicate that crop yield by fruit trees will increase as global levels of CO2 continue to rise, at least in those species that experience source limitation during fruit development.