Levels Of Carbohydrate Reserves Research Articles

Impact of carbohydrate metabolism pathways on bearing habit of mango (Mangifera indica L.) genotypes

Heterozygosity is the major constraint in perennial fruit crop like mango for regular bearing breeding. Majority of the popular mango varieties have irregular bearing habit. Many external and internal factors affect the bearing habit of perennial fruit crops. Among internal factors, the level of carbohydrate reserves and phytohormones plays a major role on bearing habit of fruit crops like apple, citrus, mango, litchi etc., Therefore, present research work aimed to study the carbohydrate metabolism pathways in regular and irregular mango genotypes of varying origin. A total of 30 primers were designed using in silico mining of four key genes coding for citrate synthase, alcohol dehydrogenase, sucrose phosphate synthase and trehalose phosphate synthase. These genes play important role in sugar and starch metabolism in mango. Of these specific primers, 14 showed polymorphism among the genotypes studied. Gene diversity (GD), average number of alleles per locus (An), polymorphism information content (PIC) and major allele frequency (Maf) observed were 0.45, 2.14, 0.35, 0.59, respectively. Simple sequence repeats markers grouped 63.15% studied mango genotypes of regular bearers together. Further, these markers could be utilized in a greater number of genotypes for regularity.

A Seaweed Extract-Based Biostimulant Mitigates Drought Stress in Sugarcane.

Drought is one of the most important abiotic stresses responsible for reduced crop yields. Drought stress induces morphological and physiological changes in plants and severely impacts plant metabolism due to cellular oxidative stress, even in C4 crops, such as sugarcane. Seaweed extract-based biostimulants can mitigate negative plant responses caused by drought stress. However, the effects of foliar application of such biostimulants on sugarcane exposed to drought stress, particularly on plant metabolism, stalk and sugar yields, juice purity, and sugarcane technological quality, have received little attention. Accordingly, this study aimed to evaluate the effects of foliar application of a seaweed extract-based biostimulant on late-harvest sugarcane during the driest period of the year. Three experiments were implemented in commercial sugarcane fields in Brazil in the 2018 (site 1), 2019 (site 2), and 2020 (site 3) harvest seasons. The treatments consisted of the application and no application of seaweed extract (SWE) as a foliar biostimulant in June (sites 2 and 3) or July (site 1). The treatments were applied to the fourth ratoon of sugarcane variety RB855536 at site 1 and the fifth and third ratoons of sugarcane variety SP803290 at sites 2 and 3, respectively. SWE was applied at a dose of 500 ml a.i. ha−1 in a water volume of 100 L ha−1. SWE mitigated the negative effects of drought stress and increased stalk yield per hectare by up to 3.08 Mg ha−1. In addition, SWE increased stalk sucrose accumulation, resulting in an increase in sugar yield of 3.4 kg Mg−1 per hectare and higher industrial quality of the raw material. In SWE-treated plants, Trolox-equivalent antioxidant capacity and antioxidant enzyme activity increased, while malondialdehyde (MDA) levels decreased. Leaf analysis showed that SWE application efficiently improved metabolic activity, as evidenced by a decrease in carbohydrate reserve levels in leaves and an increase in total sugars. By positively stabilizing the plant’s cellular redox balance, SWE increased biomass production, resulting in an increase in energy generation. Thus, foliar SWE application can alleviate drought stress while enhancing sugarcane development, stalk yield, sugar production, and plant physiological and enzymatic processes.

Reserve Accumulation Is Prioritized Over Growth Following Single or Combined Injuries in Three Common North American Urban Tree Species

Trees that grow in urban areas are confronted with a wide variety of stresses that undermine their long-term survival. These include mechanical damage to the crown, root reduction and stem injury, all of which remove significant parts of plant tissues. The single or combined effects of these stresses generate a complex array of growth and ecophysiological responses that are hard to predict. Here we evaluated the effects of different individual and combined damage on the dynamics of non-structural carbohydrates (NSC, low weight sugars plus starch) concentration and new tissue growth (diameter increment) in young trees. We hypothesized that (i) tissue damage will induce larger reductions in diameter growth than in NSC concentrations and (ii) combinations of stress treatments that minimally alter the “functional equilibrium” (e.g., similar reductions of leaf and root area) would have the least impact on NSC concentrations (although not on growth) helping to maintain tree health and integrity. To test these hypotheses, we set up a manipulative field experiment with 10-year-old trees of common urban species (Celtis occidentalis, Fraxinus pennsylvanica, and Tilia cordata). These trees were treated with a complete array of mechanical damage combinations at different levels of intensity (i.e., three levels of defoliation and root reduction, and two levels of stem damage). We found that tree growth declined in relation to the total amount of stress inflicted on the trees, i.e., when the combined highest level of stress was applied, but NSC concentrations were either not affected or, in some cases, increased with an increasing level of stress. We did not find a consistent response in concentration of reserves in relation to the combined stress treatments. Therefore, trees appear to reach a new “functional equilibrium” that allows them to adjust their levels of carbohydrate reserves, especially in stems and roots, to meet their metabolic demand under stressful situations. Our results provide a unique insight into the carbon economy of trees facing multiple urban stress conditions in order to better predict long-term tree performance and vitality.

Drought‐induced defoliation and long periods of near‐zero gas exchange play a key role in accentuating metabolic decline of Scots pine

Drought-induced defoliation has recently been associated with the depletion of carbon reserves and increased mortality risk in Scots pine (Pinus sylvestris). We hypothesize that defoliated individuals are more sensitive to drought, implying that potentially higher gas exchange (per unit of leaf area) during wet periods may not compensate for their reduced photosynthetic area. We measured sap flow, needle water potentials and whole-tree hydraulic conductance to analyse the drought responses of co-occurring defoliated and nondefoliated Scots pines in northeast Spain during typical (2010) and extreme (2011) drought conditions. Defoliated Scots pines showed higher sap flow per unit leaf area during spring, but were more sensitive to summer drought, relative to nondefoliated pines. This pattern was associated with a steeper decline in soil-to-leaf hydraulic conductance with drought and an enhanced sensitivity of canopy conductance to soil water availability. Near-homeostasis in midday water potentials was observed across years and defoliation classes, with minimum values of -2.5MPa. Enhanced sensitivity to drought and prolonged periods of near-zero gas exchange were consistent with low levels of carbohydrate reserves in defoliated trees. Our results support the critical links between defoliation, water and carbon availability, and their key roles in determining tree survival and recovery under drought.

Influence of initial levels of carbohydrates, fructans, nitrogen, and soluble proteins on regrowth of Lolium perenne L. cv. Bravo following defoliation

An experiment was designed to evaluate the role of N and C reserves on regrowth of Lolium perenne cv. Bravo following defoliation. By using two nitrogen fertilization levels together with three photoperiodic conditions, plants with variable contents of water-soluble carbohydrates (43–216 mg g−1 DW in stubble) and contrasting amounts of nitrogen (7–49 mg g−1 DW) were obtained. Plants were severely defoliated and regrowth was followed for 28 d under the same environmental conditions. The yield of leaf dry matter at the end of the regrowth period was not related to the initial level of carbohydrate reserves. However, levels of fructan in leaf sheaths and in elongating leaf bases strongly influenced the shoot yield during the first 2 d following defoliation. Fructan exohydrolase activity increased 2–3-fold in sheaths and 3.5–5-fold in elongating leaf bases, suggesting that not only fructans from sheaths but also fructans from immature cells may be used as substrates for growth. In contrast, no direct relationship was found between shoot production and nitrogen or soluble protein accumulation in source organs during early regrowth. A significant correlation existed with the initial amount of soluble proteins in sheaths and in elongating leaf bases after only 6 d of regrowth.

Influence of initial levels of carbohydrates, fructans, nitrogen, and soluble proteins on regrowth of Lolium perenne L. cv. Bravo following defoliation

gen, lead to increasingly poor recovery and even death in various grass species, regardless of the most favourable An experiment was designed to evaluate the role of climatic and soil environment (Davies, 1965; Richards, N and C reserves on regrowth of Lolium perenne cv. 1993). Bravo following defoliation. By using two nitrogen fert- Growth following defoliation depends first of all on ilization levels together with three photoperiodic con- the development of a photosynthetic surface (Richards, ditions, plants with variable contents of water-soluble 1993). A critical role of carbohydrate and N reserves as carbohydrates (43‐216 mg g’1 DW in stubble) and substrates for refoliation has been advocated long ago contrasting amounts of nitrogen (7‐49 mg g’1 DW) (Graber et al., 1927; Sullivan and Sprague, 1943). The were obtained. Plants were severely defoliated and hypothesis has been advanced that ‘new top growths are regrowth was followed for 28 d under the same envir- initiated and developed largely at the expense of previonmental conditions. The yield of leaf dry matter at ously accumulated organic reserves, and that their quantthe end of the regrowth period was not related to the ity and availability limit the amount of growth that will initial level of carbohydrate reserves. However, levels occur’ (Graber et al., 1927). Indeed, extensive mobilizaof fructan in leaf sheaths and in elongating leaf bases tion of non-structural carbohydrates and nitrogenous strongly influenced the shoot yield during the first 2 d compounds (Alberda, 1957; Volenec, 1986; Ourry et al., following defoliation. Fructan exohydrolase activity 1989; Prud’homme et al., 1992) occurred in the residual increased 2‐3-fold in sheaths and 3.5‐5-fold in elong- parts of defoliated plants. However, it has been pointed ating leaf bases, suggesting that not only fructans from out that a decrease in the amount of non-structural sheaths but also fructans from immature cells may be carbohydrates did not necessarily imply a causal role for used as substrates for growth. In contrast, no direct these reserves in initiating and aVecting regrowth (May, relationship was found between shoot production and 1960). In experiments in which the level of carbohydrates nitrogen or soluble protein accumulation in source have been modified by short-term exposures to darkness organs during early regrowth. A significant correlation and raised temperatures, it has been shown that the yield existed with the initial amount of soluble proteins in of leaf material after cutting was related to the percentage sheaths and in elongating leaf bases after only 6 d of of soluble carbohydrates in the stubble at the time of regrowth. cutting and that once growth was fully established, the rate became independent of the pretreatments applied

Interspecific and intraspecific variation in tree seedling survival: effects of allocation to roots versus carbohydrate reserves.

We examined interspecific and intraspecific variation in tree seedling survival as a function of allocation to carbohydrate reserves and structural root biomass. We predicted that allocation to carbohydrate reserves would vary as a function of the phenology of shoot growth, because of a hypothesized tradeoff between aboveground growth and carbohydrate storage. Intraspecific variation in levels of carbohydrate reserves was induced through experimental defoliation of naturally occurring, 2-year-old seedlings of four northeastern tree species -Acer rubrum, A. saccharum, Quercus rubra, and Prunus serotina- with shoot growth strategies that ranged from highly determinate to indeterminate. Allocation to root structural biomass varied among species and as a function of light, but did not respond to the defoliation treatments. Allocation to carbohydrate reserves varied among species, and the two species with the most determinate shoot growth patterns had the highest total mass of carbohydrate reserves, but not the highest concentrations. Both the total mass and concentrations of carbohydrate reserves were significantly reduced by defoliation. Seedling survival during the year following the defoliation treatments did not vary among species, but did vary dramatically in response to defoliation. In general, there was an approximately linear relationship between carbohydrate reserves and subsequent survival, but no clear relationship between allocation to root structural biomass and subsequent survival. Because of the disproportionate amounts of reserves stored in roots, we would have erroneously concluded that allocation to roots was significantly and positively related to seedling survival if we had failed to distinguish between reserves and structural biomass in roots.

Herbage Yield, Protein Content, and Carbohydrate Reserves in Gulf Cordgrass (Spartina Spartinae)

Gulf cordgrass (Spartina spartinae [Trin.] Merr.) is a highly productive bunchgrass that dominates thousands of hectares of marshlands along the Gulf coast. Herbage yield, protein content, and carbohydrate reserve patterns were studied for the species for 18 months on the Welder Wildlife Refuge on the central Texas coast. Plots were clipped at 1-month intervals at 10- and 20-cm stubble heights. Herbage yield and protein content were greater for plants clipped at 10-cm stubble height as compared with those clipped at 20 cm. Total nonstructural carbohydrate reserve levels in both stem bases and roots were also greater in plants clipped at the lower stubble height. Lowest carbohydrate reserve levels were recorded during periods of active growth. Results suggested that gulf cordgrass can withstand monthly removal of herbage to a height of 10 cm for a period of at least 18 months without adverse effects. The most sensitive periods for herbage removal, based on TNC and protein levels, were late summer and early fall.

Effect of Cutting During Reproductive Development on the Regrowth and Regenerative Capacity of the Perennial Grass, Phalaris aquatica L., in a Controlled Environment

Two cultivars of phalaris (Phalaris aquatica L.), Australian and Sirolan, were cut at four stages of development in a controlled environment to study factors involved in the sensitivity of phalaris to grazing during spring. Effects on tillering, regrowth after cutting and regenerative capacity after an artificially imposed summer dormant period were observed. Compared with Australian, Sirolan cut after the commencement of stem elongation was characterized by a higher degree of decapitation due to more synchronous elevation of its apices, and displayed a more severe reduction in regrowth, size of tiller bases and dormant buds and levels of carbohydrate reserves in summer relative to plants cut before stem elongation. Suppressed bud activity in tillers of Sirolan decapitated at early stem elongation, and the potential for profuse tillering associated with low bud dormancy after cutting at the early boot stage, could reduce persistence under field conditions. Relative to plants cut before stem elongation, regeneration growth after 'summer' by plants cut during reproductive development was depressed more severely for Sirolan (56-70%; P ⩽ 0·05) than Australian (28%; n.s), a result more closely related to regenerating tiller size than number. Regeneration growth did not differ significantly with stage reproductive development at cutting in either cultivar. Regenerative capacity of phalaris cut during reproductive development can be considered to depend on an increasing contribution from buds on bases of tillers decapitated when cut and a contribution from buds on intact tiller bases which declines as the stage of cutting becomes later. The balance between these source will depend on the environment.

Moderate water stress alters carbohydrate content and cold tolerance of red spruce foliage

Red spruce ( Picea rubens Sarg.) has been tested for response to many environmental stresses and found to be relatively tolerant. An explanation for this tolerance is its maintenance of high levels of carbohydrate reserves, mainly soluble sugars and starch, which change with alterations in photosynthetic capacity, rate of growth and degree of cold tolerance through the year. Red spruce saplings responded to moderate water stress in early September by depleting foliar starch and maintaining foliar soluble sugars. Foliar carbohydrate contents of water-stressed trees were restored to control levels within 1 week of rewatering. During and immediately after the water-stress period, foliage of water-stressed trees was more cold tolerant than foliage of well-watered trees as measured by relative electrolyte leakage. Two months after termination of the water-stress treatment, starch content of fine roots and cold tolerance of foliage of well-watered trees were significantly higher than those of water-stressed trees. Before the trees became fully cold tolerant, differences between treatments in the degree of foliar cold tolerance were positively associated with differences in soluble sugar content. As trees became more cold tolerant, soluble sugar contents were not related to the degree of cold tolerance. These results suggest that species with substantial reserves withstand periods of reduced carbon fixation by utilizing reserves for maintenance; however, lowered reserves could result in increased susceptibility to subsequent stresses.

Vigour and non-structural carbohydrates in young prune trees

To determine if differences in vegetative vigour are related to carbon partitioning in trees, three rootstck clones (i.e. Marianna GF8.1, Ishtara® and St. Julien Pixy 2879), inducing vigorous or dwarfing graft combinations with two Prunus domestica L. scion genotypes, were studied. Three years after planting in the orchard, just before bud burst, partitioning of dry matter and carbohydrate content were determined in the different parts of the tree. Dry matter, starch and soluble carbohydrate distribution in Spring were slightly affected by the rootstock. During Year 4 after planting, sorbitol, soluble sugar and starch content were determined monthly in the trunk wood. The relationship between vegetative vigour and carbohydrate content depended on the type of carbohydrate examined and on the season. The kinetics of starch mobilization were modified with the dwarfing rootstock when compared with the other rootstocks. Differences in the kinetics of starch accumulation were observed between the two cultivars which showed the same vigour. The level of carbohydrate reserves in perennial parts did not appear to be related to rootstock-induced modification of vegetative vigour.

Effect of intensity and frequency of defoliation on aerial growth and carbohydrate reserve levels inAcacia karrooplants

Acacia karroo trees were defoliated by goats at two intensities and four frequencies; 2, 4, 8 and 12‐weekly. Leaf accumulation and carbohydrate reserve levels were compared to a non‐defoliated control, and to plants (defoliation controls) which were defoliated for the first time that season each time a frequency treatment was defoliated. These plants are activated by defoliation in such a manner that successive defoliations can result in this activation being additive. There is clearly a defoliation level below which they are not activated. Activation appears to be negated to a degree by defoliations at 2 and 4‐weekly frequencies, relative to the 8‐weekly defoliation frequency. The 12‐weekly frequency at heavy defoliation produced less than the same defoliation at 8‐weekly frequency. The 2‐weekly frequency treatments produced as much leaf as the 4 and 12‐weekly defoliations at the same defoliation intensity. The more frequently plants were defoliated, the more carbohydrate reserves dropped. However, plant...

Drought and shade interact to cause fine-root mortality in Douglas-fir seedlings

Both desiccation and depleted carbohydrate reserves have been suggested as causes of fine-root (≤2 mm in diameter) mortality in trees. In this study, Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings were subjected to four combinations of shading and watering to determine whether shading increases drough-induced root mortality and, if so, whether this effect is due to reduced levels of carbohydrate reserves or increased susceptibility to desiccation. Two correlated measures of root mortality (counting root tips and weighing roots) showed that significantly more fine roots died only when seedlings were both shaded and unwatered. Concentrations of suberin, a compound synthesized by plant roots to control desiccation, were unaffected by any combination of shading and watering; however, carbohydrate reserves were nearly exhausted in the shaded and unwatered treatment — the treatment with highest root mortality. Water stress may have increased root mortality indirectly by increasing root temperature and maintenance respiration and by inhibiting photosynthate transport to the root system, but massive die-off in response to drought was apparent only when starch and sugar reserves were nearly depleted. Drought cannot be considered directly responsible for death of fine roots. Instead, a root's ability to continue to respire, which in turn depends on the status of its starch and sugar reserves, seems to be the primary physiological control of fine-root mortality.

First growing period development of Acer saccharum stump sprouts arising after different dates of cut

The study was conducted on a clear-cut area of the Nashwaak Experimental Watershed Project, New Brunswick. Thirty residual Acer saccharum Marsh, trees (6–10 cm diameter at breast height) were cut during the dormant period and at intervals during the subsequent growing period. Development of dominant and codominant sprouts on stumps of these trees was monitored. Rate of leaf pair and supporting internode production, number of leaf pairs and supporting internodes produced, rate of elongation of sprouts, total length of sprouts, rate of increase of lamina area, and total lamina area of sprouts decreased with each successive date of cut. Lamina area of successive leaf pairs and lengths of successive internodes increased acropetally to maxima and then decreased. Sylleptic shoots developed in axils of proximal leaf pairs. On sprouts arising after the dormant-period cut and after mid-June through mid-July cuts, terminal buds formed, whereas on sprouts arising after late July and August cuts, leaf pair and supporting internode production continued until meristems were killed by frost. On some sprouts arising after the dormant-period cut, adventitious roots were observed. The influence on sprout development of carbohydrate reserve levels, photoperiod, solar radiation, and depth of rest in dormant buds at the time of cut are discussed.

Kohlehydratgehalte und Vitalität isolierter Rhizome von Phragmites australis, Schoenoplectus lacustris und Typha latifolia nach mehrwöchigem O2-Mangelstreß

The lowest levels of carbohydrate reserves were found in summer in the rhizomes of Phragmites communis, Schoenoplectus lacustris and Typha latifolia. Detached rhizomes of these plants were placed under oxygen deprivation stress for 1—3 weeks and then restored to air to give a total experimental time of 6 weeks. During the oxygen stress there was a reduction in carbohydrate reserves in all the species. Schoenoplectus lacustris possessed the greatest starch reserves and during the period of stress mobilised starch, while the free sugar concentration remained unchanged. In Phragmites australis and Typha latifolia both free sugars and starch were reduced. Typha latifolia in contrast to the other species survived only two weeks of oxygen stress. Six weeks after the beginning of the experiment the rhizomes were tested for vitality and regeneration ability. Schoenoplectus lacustris rhizomes always contained the greatest carbohydrate reserves and not only survived the anoxic treatment but quickly grew both roots and green shoots during the subsequent period of aeration. Phragmites australis possessed smaller carbohydrate reserves yet regenerated successfully after all the experimental stress treatments. Typha latifolia however survived only partially, did not grow either new shoots or roots and showed a continually falling level of carbohydrate reserves. In Phragmites australis and Schoenoplectus lacustris the supply of carbohydrate was assured both by the availability of sufficient reserves and the prompt re-establishment of photosynthesis. In Typha latifolia the low level of carbohydrate reserves present in summer limited its tolerance of oxygen deprivation.

Physiology of feeding preference patterns of female black blowflies (Phormia regina Meigen)

The relative effectiveness of 0. 1 M sucrose and 10% yeast extract in eliciting feeding by femalePhormia regina has been shown to be related to the fly's carbohydrate reserve levels. Females that have had ad lib. access to 0.1 M sucrose (S flies, standard condition) take larger drinks of 10% yeast than 0.1 M sucrose starting at three days of age, indicating that 10% is the more effective feeding stimulus. Females that have had ad lib. access to 0.1 M sucrose and 10% yeast (S/Y flies, standard condition) always drink more 0.1 M sucrose than 10% yeast (Fig. 1). S/Y (standard condition) flies appear to respond to the yeast as if it were dilute carbohydrate: the volumes of 0.1 M sucrose and 10% yeast that they drink fluctuate in parallel. S (standard condition) flies respond to the yeast differently: starting day 3, their drink volumes of 10% yeast increase as drink volumes of 0.1 M sucrose decrease.

Sprouting and Carbohydrate Reserves of Two Wildland Shrubs following Partial Defoliation

Highlight: Two wildland shrubs, little rabbitbrush and snowberry, were subjected to three intensities of defoliation at each of four distinct stages in the carbohydrate Rserve cycle. These treatments, comparable to browsing and other forms of natural defoliation, were designed to determine the effects on sprouting and associated carbohydrate reserve levels the following spring. Little rabbitbrush plants had reduced carbohydrate reserves, shorter sprouts, and more sprouts following most defoliation tretments. In contrast, carbohydrate reserves increased in snowberry plants with all intensities of defoliation, but there were no significant variations in their sprouting characteristics. Most dormant buds on the root crowns of little rabbitbrush and snowberry plants that were protected from defoliation were prevented from developing as basal sprouts because of apical dominance. Removal of twig tips, however, stimulated more of these buds to produce sprouts. Once a sprout began to grow, a direct relationship seemed to exist between its elongation and the amount of carbohydrate reserves available to it.

Carbon Balance of the Sultana Vine (Vitis vinifera L.) And the Effects of Autumn Defoliation by Harvest-Pruning

Components of the carbon balance in the Sultana vine (Vitis vinifera L.) were examined with emphasis on the autumn, post-harvest, period. The net photosynthetic rate (PN) of leaves decreased from 0.30 to 0.03 mg CO2 m-2 s-1 from January to May (late summer to autumn). Two-thirds of this decline cocurred in the month before leaf fall. This decline in PN as senescence progressed was mainly due to increases in the 'residual', non-gas-phase, resistance to CO2 transfer. 14C-labelled assimilates were shown to move from the leaves to the perennial portions of the vine in both early and late autumn, and this 14C label reappeared in the shoot growth of the following spring. However, the level of carbohydrate reserves in shoots, roots or trunk in the autumn to spring period was not significantly affected by a severe (c. 60%) defoliation in early autumn. This level of defoliation, which the vine is able to tolerate without cumulative effects, occurs where Sultana vines are 'harvest-pruned' as part of the harvesting method of trellis drying.

Defoliation Effects on Root Weights and Total Nonstructural Carbohydrates of Blue Grama and Western Wheatgrass1

Several studies have indicated that clipping or grazing reduces root weights, whereas other studies have indicated little or no change in root weights after defoliation. Root production and carbohydrate reserve stores are important in maintaining forage production after defoliation. Therefore, the effects of intensive defoliations on root weights and carbohydrate reserves of blue grama [Boutelotta gracilis (H.B.K.) Lag.] and western wheatgrass (Agropyron smithii Rydb.) were studied on a shortgrass prairie range. Small differences in root weights among undefoliated and heavily defoliated blue grama and western wheatgrass plants were found. However, undefoliated western wheatgrass plants had significantly more carbohydrate reserves than did the defoliated plants. Resistance of blue grama to grazing may be related to its ability to maintain a vigorous root system and carbohydrate reserve levels after defoliation.

Studies on the Performance of Alfalfa Swards : V. Relationships between top weight and carbohydrate root reserves of individual plants under sward conditions

1. Behaviours of dead plants in alfalfa swards grown in a series of slot-like soil containers were observed in detail and levels of carbohydrate reserves in a root of dead plants were inferred. 2. Occurrences of dead plants in swards seemed to increase when swards received too frequent cutting or no cutting. 3. Most of the dead plants in swards with cutting treatments were the plants that could never start to regrow after cuttings. There were few plants that could start to regrow and died in process of growing. 4. Percentages of carbohydrate reserves in a root of individual plants seemed to rise sharply with increasing top weights to a maximum which was constant for all higher top weights. 5. Levels of carbohydrate reserves in a root of dead plants in swards with cutting treatments, as compared with those of the alive plants in the swards, were remarkably low at cutting time. Also in swards without cutting treatments, levels of carbohydrate reserves in a root of dead plants seemed remarkably low, as compared with those of the alive plants in the swards.