Root Starch Reserves Research Articles

Effect of Different Plucking Systems on Yield and Root Starch Reserve in Two Cultivars of Tea (Camellia sinensis L.)

A study was carried out to monitor the effect of different plucking systems on root starch reserve and yield of tea in two cultivars (drought tolerant TRI2025 and moderately drought tolerant TRI2026). Depending on the severity of plucking, four plucking systems were used as treatments namely, mother-leaf plucking, fish-leaf plucking, janam-leaf plucking and estate practice. The cultivar TRI2026 showed significantly higher yield than the drought tolerant cultivar TRI2025. Estate practice produced greater yield in TRI2025 than the other treatments, while in TRI2026 the highest yield was found in fish-leaf plucking system. Although cultivars had no significant effect on root starch reserves, however significantly different found in treatments. About one year after commencing the experiment, for both cultivars higher root starch observed under mother-leaf plucking and the lowest was in janam-leaf plucking.J. Environ. Sci. & Natural Resources, 9(2): 91-95 2016

Root Starch Reserves Are Necessary for Vigorous Re-Growth following Cutting Back in Lotus japonicus

Perenniality and vegetative re-growth vigour represent key agronomic traits in forage legume (Fabaceae) species. The known determinants of perenniality include the conservation of the vegetative meristem during and after the flowering phase, and the separation of flowering from senescence. The ability of the plants to store nutrient resources in perennial organs and remobilize them may also play an important role in the perennial growth habit, and in determining the capacity of the plant to re-grow following grazing or from one season to the next. To examine the importance of stored starch, we examined the vegetative re-growth vigour following cutting back of a unique collection of Lotus japonicus mutants impaired in their ability to synthesize or degrade starch. Our results establish that starch stored in the roots is important for re-growth vigour in Lotus japonicus. We extended this analysis to a collection of Lotus (trefoil) species and two ecotypes of Lotus japonicus displaying a large variation in their carbohydrate resource allocation. There was a positive correlation between root starch content and re-growth vigour in these natural variants, and a good general correlation between high re-growth vigour and the perennial life-form. We discuss the relationship between perenniality and the availability of root carbohydrates for re-growth.

Fertilization of lodgepole pine trees increased diameter growth but reduced root carbohydrate concentrations

Tree growth variables and more complex derived variables such as vigor index have all been linked to the ability of lodgepole pine (Pinus contorta var latifolia) trees to defend against insect herbivores, particularly mountain pine beetle (Dendroctonus ponderosae Hopkins, Coleoptera: Curculionidae). These variables are considered indirect measures of carbohydrate reserves. Trees with high vigor index values have high growth rates and are assumed to have high carbohydrate reserves. However, this critical assumption was untested for lodgepole pine. In this paper we evaluated the relationship between carbohydrate concentration and tree characteristics. We measured concentrations of root starch in 10 pure lodgepole pine stands of different ages in the Canadian Rockies which had been fertilized, thinned, fertilized and thinned or left untreated in a 2×2 factorial design. Both fertilization and thinning increased basal area increment while only fertilization increased lateral branch growth in the crown. Contrary to expectations, fertilization decreased root starch reserves although it increased basal area increment; thinning had no effect on root carbohydrates. Root starch reserves were positively related to basal area increment and vigor index in both fertilized and unfertilized plots, however, the best predictors of starch reserves were height-to-live-crown and cambial surface area below the live crown; starch reserves declined as both of these variables increased. These data suggest that large carbon sinks associated with long boles below the crown, and rapid growth of the crown and stem as a result of fertilization are detrimental to building starch reserves in the roots.

Juggling carbon: allocation patterns of a dominant tree in a fire-prone savanna

In frequently burnt mesic savannas, trees can get trapped into a cycle of surviving fire-induced stem death (i.e. topkill) by resprouting, only to be topkilled again a year or two later. The ability of savanna saplings to resprout repeatedly after fire is a key component of recent models of tree-grass coexistence in savannas. This study investigated the carbon allocation and biomass partitioning patterns that enable a dominant savanna tree, Acacia karroo, to survive frequent and repeated topkill. Root starch depletion and replenishment, foliage recovery and photosynthesis of burnt and unburnt plants were compared over the first year after a burn. The concentration of starch in the roots of the burnt plants (0.08 +/- 0.01 g g(-1)) was half that of the unburnt plant (0.16 +/- 0.01 g g(-1)) at the end of the first growing season after topkill. However, root starch reserves of the burnt plants were replenished over the dry season and matched that of unburnt plants within 1 year after topkill. The leaf area of resprouting plants recovered to match that of unburnt plants within 4-5 months after topkill. Shoot growth of resprouting plants was restricted to the first few months of the wet season, whereas photosynthetic rates remained high into the dry season, allowing replenishment of root starch reserves. (14)C labeling showed that reserves were initially utilized for shoot growth after topkill. The rapid foliage recovery and the replenishment of reserves within a single year after topkill implies that A. karroo is well adapted to survive recurrent topkill and is poised to take advantage of unusually long fire-free intervals to grow into adults. This paper provides some of the first empirical evidence to explain how savanna trees in frequently burnt savannas are able to withstand frequent burning as juveniles and survive to become adults.

Root carbohydrates and aspen regeneration in relation to season of harvest and machine traffic

Season of harvest has often been suggested as a driver for the erratic success of aspen ( Populus tremuloides) sucker regeneration, partially due to root carbohydrate reserves and soil conditions at the time of harvest. A field experiment in western Manitoba, Canada, assessed root suckering and root carbohydrates of aspen in response to season of harvest and machine traffic. Six sites (120 m × 120 m) were selected within two large mature aspen stands slated for summer harvest. Plots (50 m × 50 m) were hand-felled (without machine traffic) in mid-summer, late summer, winter, and one plot was left uncut as a control. Season of cut with no traffic had no effect on sucker density, height or leaf dry mass per sucker. During the dormant season, root starch reserves were highest in the winter cut plots, however, just prior to suckering, this difference in carbohydrate reserves among the three seasons of harvest disappeared and by the end of the first growing season root reserves in all three seasons of cut had recovered to near control levels. Adjacent plots that were conventionally harvested in the summer and impacted by logging traffic had similar sucker densities but had 19% less height growth of suckers and 29% less leaf dry mass per sucker compared to suckers in plots harvested at the same time without traffic. After one growing season, root carbohydrate levels were similar whether or not machine traffic was used; however, the reduction in leaf dry mass in plots with machine traffic could have negative implications for carbohydrate accumulation and growth. The study suggests that the phenological state of the mature aspen plays a very small role in aspen regeneration and that harvesting practices and site conditions are likely the main drivers of aspen regeneration success.

A model of pecan tree growth for the management of pruning and irrigation

Pecans [ Carya illinoensis (Wangenh.) C. Koch] are an important cash crop in arid southwestern USA. The pecan is an alternate bearing tree and its water use is greater than that of most row crops. Irrigation, pruning amount, and timing must be effectively managed to reduce alternate bearing for maximum profits. A simulation model of pecan growth and yield is a potential tool for managing irrigation and pruning amounts and timing. An object-based pecan growth model was developed and validated to simulate daily pecan tree dry matter production, biomass allocation to leaves, nuts, trunk, and branches, and alternate bearing according to inputs of weather data, soil condition, irrigation, and pruning operations. Daily dry matter production per unit of evapotranspiration (water use efficiency) was calculated as a function of average vapor pressure deficit. Biomass allocation functions were derived from tree growth measurements at an orchard near Las Cruces, NM. Alternate bearing was simulated as a function of the level of root starch reserves. It was theorized that the setting of pistillate flowers and subsequent nut yields are proportional to the level of root starch reserves in the preceding dormant phase (winter). Mathematical functions for the effects of irrigation and pruning on tree growth and yield were derived from the literature and available data. The model was calibrated using 2002, historical, and literature data and validated against 2003 and 2004 data obtained from a mature pecan (Western Schley cultivar) orchard near Las Cruces, NM. Overall accuracy was above 89% for simulated total dry matter production, nut yield, tree height, and diameter at breast height (DBH). This model was found to adequately simulate the effects of climate, irrigation, and pruning on pecan tree growth, nut yield, and alternate bearing. It can potentially be used to schedule and estimate the amount of irrigation and pruning to optimize pecan nut yield.

Fertilization of boreal forest reduces both autotrophic and heterotrophic soil respiration

AbstractThe boreal forest is expected to experience the greatest warming of all forest biomes, raising concerns that some of the large quantities of soil carbon in these systems may be added to the atmosphere as CO2. However, nitrogen deposition or fertilization has the potential to increase boreal forest production and retard the decomposition of soil organic matter, hence increasing both tree stand and soil C storage.The major contributors to soil‐surface CO2 effluxes are autotrophic and heterotrophic respiration. To evaluate the effect of nutrient additions on the relative contributions from autotrophic and heterotrophic respiration, a large‐scale girdling experiment was performed in a long‐term nutrient optimization experiment in a 40‐year‐old stand of Norway spruce in northern Sweden. Trees on three nonfertilized plots and three fertilized plots were girdled in early summer 2002, and three nonfertilized and three fertilized plots were used as control plots. Each plot was 0.1 ha and contained around 230 trees. Soil‐surface CO2 fluxes, soil moisture, and soil temperature were monitored in both girdled and nongirdled plots.In late July, the time of the seasonal maximum in soil‐surface CO2 efflux, the total soil‐CO2 efflux in nongirdled plots was 40% lower in the fertilized than in the nonfertilized plots, while the efflux in girdled fertilized and nonfertilized plots was 50% and 60% lower, respectively, than in the corresponding nongirdled controls. We attribute these reductions to losses of the autotrophic component of the total soil‐surface CO2 efflux. The estimates of autotrophic respiration are conservative as root starch reserves were depleted more rapidly in roots of girdled than in nongirdled trees. Thus, heterotrophic activity was overestimated.Calculated on a unit area basis, both the heterotrophic and autotrophic soil respiration was significantly lower in fertilized plots, which is especially noteworthy given that aboveground production was around three times higher in fertilized than in nonfertilized plots.

INFLUENCE OF SUGAR MAPLE HEALTH ON FECUNDITY OF PEAR THRIPS IN MASSACHUSETTS

AbstractWidespread defoliation of sugar maple stands due to pear thrips,Taeniothrips inconsequens(Uzel), feeding occurred in Massachusetts in 1987 and 1988. To assess the role of tree health as a possible cause of these outbreaks, an experiment was conducted in sugar maple stands in Massachusetts in 1990. Sleeve cages were placed on mature sugar maples and stocked with adult female pear thrips to determine the relation between root starch reserves (an index of tree health) and thrips fecundity. The experiment was run at four sites, assessing both root starch levels and thrips fecundity on individual trees. Each stand showed a range from high to low starch values and trees at each end of the root starch index spectrum were selected for use in the experiment at each site. Analysis of data showed no differences between sites, apart from those linked to starch levels, and found thrips fecundity to be positively correlated with higher starch reserves. The results of this experiment do not support the original hypothesis that declining tree health was a causal factor in pear thrips outbreaks on sugar maple in Massachusetts.

Can Tree Susceptibility to Borers be Predicted from Root Starch Measurements?

The twolined chestnut borer (TLCB) attacks and kills stressed oak trees, especially those that have been weakened by severe drought. We tested the hypothesis that winter root starch reserves of white oak are an indicator of tree vigor, and that trees low in stored starch are especially vulnerable to borer attack during the following summer. Only those trees that were very low in stored root starch were heavily attacked by the TLCB and showed signs of decline or died. A few oaks with high starch reserves were also successfully colonized, but those trees did not show signs of decline and did not die. Thus, winter starch reserves were generally a good predictor of TLCB attacks. Further research is needed to determine if this relationship holds for other hardwood trees and their respective wood borers. Use of root starch ratings to assess tree susceptibility to borers needs further testing in urban settings to determine its practicality for pest management.

Winter starch reserves of white oak as a predictor of attack by the twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae)

The twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae), attacks oaks (Quercus spp.) and is associated with extensive mortality of trees in the eastern deciduous forests of North America. We tested the hypothesis that winter starch reserves of oak roots are an indicator of tree vigor and that only trees low in stored starch would be attacked by A. bilineatus. We measured the levels of stored starch in the roots of 200 non-infested healthy white oaks during the dormant season and determined their correlation with A. bilineatus attacks the following spring. There was a significant increase in A. bilineatus captures on sticky traps with a decrease in winter starch reserves. Trees low in stored starch that were also stressed by phloem-girdling attracted 3.7 times as many beetles as did non-girdled trees that were low in starch. However, non-girdled trees that had low winter starch reserves were also attacked. Only oaks that had had extremely low winter root starch reserves (<5mg/g dry weight of root sapwood tissue) were heavily attacked by A. bilineatus and subsequently died. One third of non-girdled low starch trees and 67% of phloem-girdled low starch trees died, whereas none of the trees with root starch >5 mg/g dry wt died. These results indicate that winter starch reserves are a good predictor of A. bilineatus attack.

The role of root nutrient reserves in regrowth of two savanna shrubs

The critical nutrient(s) limiting vegetative regrowth following shoot destruction by burning or cutting were identified in two neotropical savanna shrubs, Miconia albicans and Clidemia sericea, growing in the Mountain Pine Ridge Forest Reserve, Belize. Only starch, and not Ca, Mg, K, or P, was significantly depleted in the roots of these shrubs after both a single burn and repeated annual burns. Phosphorus was depleted only after repeated burns, while the other mineral nutrients showed no significant decline. In roots that failed to sprout following repeated shoot cuttings at 2-month intervals, phosphorus was reduced by 35–45% and starch was reduced by 97–98% compared with unburned roots. Therefore, root starch was indicated as a critical nutrient that limited resprouting ability. Root starch reserves were replenished to preburn levels within 2 years following a burn, suggesting that a cumulative net decline would occur only with annual burning. The decline in root starch was paralleled by a decline in growth of 1-year-old shoots under annual burning.