Total Nonstructural Carbohydrate Concentration Research Articles

Physiological tipping points to light reduction underlie seagrass population collapse and abrupt shift in a shallow coastal lagoon

Physiological tipping points to light reduction underlie seagrass population collapse and abrupt shift in a shallow coastal lagoon

氮素水平对茶树叶片氮代谢关键酶活性及非结构性碳水化合物的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 氮素水平对茶树叶片氮代谢关键酶活性及非结构性碳水化合物的影响 DOI: 10.5846/stxb201810112203 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 湖南农业科技创新资金项目（2017JC17）；2018年度湖南省重点研发计划项目（2018NK2032）；湖南省自然科学基金（2017JJ3167） Effects of nitrogen levels on key enzyme activities and non-structural carbohydrates in nitrogen metabolism in tea leaves Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以福鼎大白茶（FD）、保靖黄金茶1号（HJ1）、白毫早（BHZ）为材料，设置不施氮N0（0 g）、低氮N1（11 g）、中氮N2（22 g）和高氮N3（33 g）4个氮素水平的盆栽实验，研究了铵态氮对3个品种茶树的根系活力、氮代谢关键酶及非结构性碳水化合物（NSC）的影响。结果表明：随着施氮水平的提高，N2、N3处理的茶树根系活力较对照N0显著增加（P<0.05），但二者间无显著差异；叶片谷氨酰胺合成酶（GS）、谷氨酸合成酶（GOGAT）活性总体呈上升趋势；与对照比较，茶树叶片全氮和可溶性蛋白含量增加，其中HJ1在N2和N3处理后显著增加（P<0.05）；在3个茶树品种中，非结构性碳水化合物中可溶性总糖含量均呈上升趋势，淀粉含量具有品种特异性，施氮处理后3个茶树品种氮代谢关键酶活性及NSC含量变化存在差异，以HJ1的氮同化关键酶GS、GOGAT酶活性较高、根系活力较强，氮代谢产物显著增加，表明其具有较高的氮同化速率。施氮后HJ1的总NSC的含量及碳氮比的变化幅度较另外2个品种小，能够更好的保持碳氮平衡，游离氨基酸含量增幅较高，品质更优。因此，通过茶树氮代谢关键酶活性及非结构性化合物的研究能为茶树品种的品质评价以及提高茶树的品质和氮素利用效率提供依据。 Abstract:We investigated the effects of nitrogen on root activity, key enzyme activities of nitrogen metabolism, and non-structural carbohydrates (NSC) in 3 tea varieties (Fuding dabai tea (FD),Baojing huangjin tea 1# (HJ1) and Baihaozao (BHZ)) with 4 ammonium nitrogen (N) treatments:without N deposition:N0 (0 g), low N deposition:N1 (11 g), medium N deposition:N2 (22 g), and high N deposition:N3 (33 g). The results showed that root activity increased significantly in N2 and N3 compared with the control, however, there were no differences between these two treatments. The GS and GOGAT activities in tea leaves increased after N treatment. Compared with the control, the total nitrogen content and soluble protein content in tea leaves generally increased following nitrogen treatment, significantly in the case of N2 and N3 in HJ1 (P<0.05). As the mass of N in the treatment increased, the NSC and total soluble sugars presented a tendency of increasing. However, the changes in starch content displayed varietal specificities in FD, HJ1 and BHZ. Changes in key enzymes involved in nitrogen metabolism and NSC content were observed after nitrogen treatment, which were different in the 3 tea varieties. Following N treatment, HJ1 showed higher GS and GOGAT activities, higher root activity, and a significant increase of nitrogen metabolites compares to FD and BHZ, which indicates a higher rate of nitrogen assimilation. The total NSC content and C/N changed less in HJ1, which had a better quality of higher free amino acid content, implying that HJ1 better maintain a carbon-nitrogen balance. Therefore, research on the activities of key enzymes involved in nitrogen metabolism and NSC in tea plants can provide a basis for evaluating the quality of tea varieties and improving the quality and nitrogen use efficiency of tea plants. 参考文献 相似文献 引证文献

Apple fruit set is influenced by altered floral bud density but not by reduced carbohydrate reserves

The extent to which carbohydrate reserves contribute to apple (Malus × domestica Borkh.) fruit set is unclear. On ‘Royal Gala’/‘M9’ trees, we used postharvest early defoliation (12 days after harvest) to alter carbohydrate reserve accumulation compared with natural leaf fall. Superimposed over this, late winter bud thinning using artificial spur extinction (ASE, 6 buds cm(-1) branch cross sectional area) to manipulate the number of developing sinks in spring was compared with unmodified trees. Reducing bud density using ASE did not affect the concentration of total non-structural or soluble carbohydrates in root or spur tissues sampled at intervals from dormancy to final fruit set. However, ASE increased within-bud fruit set compared with unmodified trees. Early defoliation did not affect fruit set compared with natural defoliation, but reduced concentrations of total non-structural carbohydrates in roots in winter by 44% (264 to 147 mg g(-1) dry weight) and concentrations of starch in spurs in winter by 60% (19 to 7.7 mg g(-1)). Between dormancy and 1 week before bloom (WBB), total non-structural carbohydrate concentration declined in roots of naturally defoliated trees by 31%, and in spurs of naturally and early defoliated trees by 37 and 46% (respectively). In trees defoliated early, concentrations of total non-structural carbohydrates increased from their minimum at 1WBB in spurs and 2 weeks after bloom (WAB) in roots. In naturally defoliated trees total non-structural carbohydrates did not increase in roots during the measurement period, but increased in spurs between 5 and 9 WAB. Lack of differences in fruit set among defoliation treatments despite differences in non-structural carbohydrate concentration in spurs and roots implied that at concentrations observed here, stored carbohydrates in these tissues had little role in fruit set. This was supported by observations that total non-structural carbohydrate concentration declined before full bloom, not during fruit set, and total non-structural carbohydrate concentration increased during the period 2 to 4 WAB, when limitations in carbohydrate resources are thought most likely to affect fruit set.

Changes of non-structural carbohydrates of Pinus sylvestris var. mongolica seedlings in the process of drought-induced mortality

To understand the distribution of non-structural carbohydrates (NSC) and adaptive mechanism in the process of drought-induced mortality, two-year-old Pinus sylvestris var. mongolica seedlings were grown under continuous natural drought condition. Needle water potential and the contents of soluble sugar, starch and total NSC in different organs (current-year-old needles, one-year-old needles, stems, coarse roots and fine roots) of the seedlings were measured when soil water content decreased to 60%, 40%, 30%, 20% and 15% of the soil field water capacity (SFC). The results showed that when the soil water content decreased from 40% SFC to 15% SFC, there was no significant change in needle water potential at predawn and midday. When soil water content decreased from 60% SFC to 30% SFC, the contents of soluble sugar, starch, total NSC and the ratio of soluble sugar and starch first decreased and then increased in all organs. When soil water content dropped from 30% SFC to 20% SFC, the soluble sugar, starch and total NSC contents decreased in the current-year-old needles, one-year-old needles, stems and fine roots. The soluble sugar content increased, but the starch and total NSC contents decreased in the coarse roots. When soil water content decreased from 20% SFC to 15% SFC, the contents of soluble sugar, starch and total NSC decreased in the current-year-old needles, one-year-old needles and stems, and the soluble sugar and total NSC contents decreased, but the starch content increased in the coarse roots, the soluble sugar content decreased, but the starch and total NSC contents increased in fine roots. The results indicated that NSC content in different organs of P. sylvestris var. mongolica seedlings varied in their adaptation to different degrees of drought. The contents of soluble sugar and total NSC in seedlings decreased under less than 30% of the soil field water capacity, with the starch being accumulated in the coarse roots and fine roots. The seedlings might be died due to carbon depletion.

Growth, freezing tolerance, and yield performance of alfalfa (Medicago sativaL.) cultivars grown under controlled and field conditions in northern latitudes

Alfalfa (Medicago sativa L.) is one of the most popular forage legume crops worldwide. Its cultivation in the boreal and sub-boreal zone is restricted by inadequate winter hardiness, but global warming may increase its adaptability in these latitudes. Here, we examined variation in growth and freezing tolerance of four alfalfa cultivars recommended for the northern temperate climates of Europe (Alexis, Lavo, Live, and Nexus) and two cultivars with adaptation to milder or Mediterranean climates (Rangelander and Hunter River). Two experiments under controlled conditions (growth cessation and cold acclimation experiments) along with a 2-yr field experiment were conducted. Lavo was the most freezing-tolerant cultivar in both the cold acclimation and field experiments. Both Rangelander and Hunter River showed poor freezing tolerance. Lavo responded to decreasing temperatures, unlike the response to shorter day length, by allocating biomass to the roots. In general, better freezing tolerance was associated with high total nonstructural carbohydrate and low starch content. The field experiment results revealed that the more freezing-tolerant cultivars may have some advantages regarding yield, especially in the second year, but the differences between the cultivars were modest.

Phenotypic Plasticity and Other Forage Responses to Grazing Management of Ecoturf Rhizoma Peanut

Forage–livestock systems in the southeastern United States are based on N‐fertilized perennial grass pastures, with minimal legume contribution. The legume rhizoma peanut (RP, Arachis glabrata Benth.) can persist and spread in grazed mixtures with C4 grasses, and Ecoturf RP is of particular interest because it is relatively decumbent and may vary its growth habit in response to defoliation management. The objective was to quantify effects of grazing frequency and intensity of Ecoturf on herbage accumulation (HA), canopy characteristics, storage organ mass, and total nonstructural carbohydrate (TNC) concentration. Treatments were the factorial combinations of three levels of regrowth interval (RI; 1, 4, and 7 wk) between grazing events and two levels of post‐grazing stubble height (SH; 4 and 8 cm). For the 4‐cm SH, HA increased from 8.4 to 10.5 Mg ha−1 in 2015 and from 9.8 to 13.6 Mg ha−1 in 2016 as RI decreased from 7 to 1 wk. The effect of RI was less pronounced for the 8‐cm SH. When grazed to a 4‐cm SH, herbage bulk density and post‐grazing leaflet mass increased linearly as RI decreased from 7 to 1 wk in both years. Changes in root‐rhizome mass and TNC pool during 2 yr of grazing were not affected by SH or RI. Ecoturf adapted to frequent, close grazing by increasing herbage bulk density and positioning leaves close to the soil surface, allowing rapid regrowth after defoliation without depleting reserves. Ecoturf is tolerant of a range of grazing strategies, showing promise for use in pastures.

Stem Carbohydrates and Adventitious Root Formation of Cycas micronesica following Aulacaspis yasumatsui Infestation

Large stem cuttings were removed from Cycas micronesica K.D. Hill trees and used for asexual propagation to more fully understand resource factors that influence adventitious root formation success. Healthy source trees had received insecticide protection from ubiquitous Aulacaspsis yasumatsui Takagi infestations and unhealthy source trees had suffered from chronic A. yasumatsui infestations. Nonstructural carbohydrates were quantified from stem tissues at the base of each 1-m cutting, and induction of adventitious roots was attempted using field soil as the medium. Carbohydrate concentrations were increased in healthy, protected tree cuttings above those in unhealthy, infested tree cuttings. The relative increase was greatest in the hexoses, intermediate in sucrose, and least in starch. The total nonstructural carbohydrate concentration in cuttings of infested trees was 54% of that of protected trees, and the sugar/starch quotient of infested trees exceeded that of protected trees. Asexual propagation success was 30% for the unhealthy tree cuttings and 100% for the healthy tree cuttings. These manipulative experiments confirm that chronic A. yasumatsui herbivory of C. micronesica trees reduces stem carbohydrates and decreases asexual propagation success. The results indicate that the use of large cuttings from unhealthy C. micronesica trees to rescue tree populations from construction sites is not a wise conservation decision in habitats where A. yasumatsui herbivory has been uncontrolled. Protocols for future rescue operations designed to transplant C. micronesica trees from construction sites may be improved by this new knowledge.

Non-Structural Carbohydrate Dynamics in Leaves and Branches of Pinus massoniana (Lamb.) Following 3-Year Rainfall Exclusion

Drought-induced tree mortality is an increasing and global ecological problem. Stored non-structural carbohydrates (NSCs) may be a key determinant of drought resistance, but most existing studies are temporally limited. In this study, a 3-year 100% rainfall exclusion manipulation experiment was conducted to evaluate the response of NSC dynamics to drought stress in 25-year-old Pinus massoniana leaves and branches. The results showed: (1) compared with the control condition, leaf NSC concentration in the drought treatment increased 90% in the early stage (days 115–542) (p &lt; 0.05), and then decreased 15% in the late stage (days 542–1032), which was attributed to water limitation instead of phenology; (2) the response of leaf NSCs to drought was more significant than branch NSCs, demonstrating a time lag effect; and (3) the response of P. massoniana to mild drought stress was to increase the soluble sugars and starch in the early stage, followed by an increase in soluble sugars caused by decreasing starch in the later stress period. Considering these results, mid-term drought stress had no significant effect on the total NSC concentration in P. massoniana, removing carbon storage as a potential adaptation to drought stress.

Nutritional composition of the diet of the northern yellow-cheeked crested gibbon (Nomascus annamensis) in northeastern Cambodia.

This study measured the nutritional composition of foods consumed by the northern yellow-cheeked crested gibbon (Nomascus annamensis) in northeastern Cambodia. One group of N. annamensis was studied, and focal animal sampling was used to observe their feeding behavior. The study was conducted for 4months (January-April 2015) in the dry season and 69 foods were collected for nutritional analyses. N. annamensis fed on 37 plant species, but only seven species made up more than 80% of feeding time. N. annamensis spent the majority of their time feeding on fruit (60.36%), followed by young leaves (22.60%), flowers (13.74%), and mature leaves (3.30%). Fruit had the highest concentrations of total non-structural carbohydrates, while young leaves had the highest concentration of crude protein compared to other food items. All food items had similar concentrations of lipids, except young leaves, which had lower levels than fruit and flowers. All plant parts consumed by N. annamensis had similar amounts of neutral detergent fiber, acid detergent fiber, and acid detergent lignin. Thirty-two percent of all food items contained condensed tannins, and they had a similar level of it. All foods also had similar energy contents. This study adds to our knowledge of the feeding ecology of N. annamensis by providing baseline data on the make-up of the foods they eat and may contribute to captive feeding programs, ultimately assisting the conservation of this species.

Effects of Elevated CO2 and Temperature on Twospotted Spider Mite (Acari: Tetranychidae) Feeding on Maize1

Abstract Climate models predict that the atmospheric CO2 concentration will double and atmospheric temperatures will increase 1.8–4.0°C globally by the end of this century. These changes will influence the growth of both crop plants and herbivores. The effects of elevated CO2 and temperature on the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), feeding on maize, Zea mays L., were examined in environmentally controlled chambers. Elevated CO2 decreased N content and increased total nonstructural carbohydrate (TNC) content and the TNC:N ratio in maize leaves. Developmental time of larvae, protonymphs, deutonymphs, and the entire immature development of T. urticae was reduced at elevated temperatures, while elevated CO2 slightly mitigated the effects of elevated temperature on developmental time. The fecundity of T. urticae declined under elevated CO2 and temperature. Tetranychus urticae had lower net reproductive rate and shorter generation time at elevated temperatures, regardless ...

Evaluation of Bermuda grass (Cynodon dactylon (L.) Pers.) and Bahia grass (Paspalum notatum Flugge) for short-term drought tolerance targeting low-maintenance landscaping

Drought responses of turf-type Bermuda grass (Cynodon dactylon (L.) Pers.) and Bahia grass (Paspalum notatum Flugge) in relation to their growth, carbon allocation and accumulation of nonstructural carbohydrates were investigated. Seedlings were exposed to a 20 day terminal drought, followed by 20 day recovery with irrigation. Leaf dry matter was lower in water-stressed plants than control plants by the end of drought, but did not differ in roots. For both species, more carbon was allocated towards roots in response to drought. Total nonstructural carbohydrate (TNC) concentration in shoots was increased in drought-stressed plants of both species. However, root TNC concentrations in Bahia grass were decreased after drought. TNC pool sizes also showed a similar variation, hence correlated with TNC concentrations. Bahia grass maintained a better quality than Bermuda grass after the drought, having recorded a higher aesthetic score, higher relative water content and a lower electrolyte leakage. Results suggest that, both species are considerably tolerant to short-term drought though Bahia grass seems more promising.Int. J. Appl. Sci. Biotechnol. Vol 6(1): 12-16

Wheatgrass Germination and Seedling Growth under Osmotic Stress

Core Ideas A physiological mechanism for drought resistance in wheatgrass is proposed.Analysis of antioxidant enzyme activity during germination of wheatgrass under drought stress.Germination, osmotic adjustment, and antioxidant enzyme activities of wheatgrass under drought stress. Osmotic stress is one of the major environmental stresses that limits plant growth and seed germination in many areas of the world. The purpose of this research was to determine the degree and range of tolerance to osmotic stress in 20 wheatgrass ecotypes to identify ecotypes that might be potentially useful in arid and semiarid regions. We used a completely randomized factorial design with two factors, five levels of osmotic stress (0, –0.2, –0.5, –0.8, and –1.6 MPa), wheatgrass ecotypes, and three replicates. Our findings suggest that AD1, AD2, AD3, and AD5 ecotypes under osmotic stress have a higher level of final germination percentage (FGP) and rate of germination (GR), although they had a lower value for the average germination time (MGT) than other ecotypes during the experiment. These results suggested that AD1, AD2, AD3, AD5, AE5, AC6, and FA ecotypes exhibited a more effective protection, along with various mechanisms, and the mitigation of oxidative damages such as lipid peroxidation through mechanisms by which enzymatic and non‐enzymatic antioxidant activities were maintained at a higher level. Also, these ecotypes showed higher proline and total nonstructural carbohydrate contents (TNC), but lower malondialdehyde content (MDA) and H2O2 content than other ecotypes. A cluster analysis found these same six ecotypes (AD1, AD2, AD3, AD5, AE5, and AC6) and FA were clustered into a group of “osmotic‐ tolerant ecotypes”. This group might be potentially useful in arid and semiarid regions.

Carbohydrate dynamics of three dominant species in a Chinese savanna under precipitation exclusion.

The potential impact of drought on the carbon balance in plants has gained great attention. Non-structural carbohydrate (NSC) dynamics have been suggested as an important trait reflecting carbon balance under drought conditions. However, NSC dynamics under drought and the response mechanisms of NSC to drought remain unclear, especially in water-limited savanna ecosystems. A precipitation exclusion experiment was performed to simulate different drought intensities in a savanna ecosystem in Yuanjiang valley in southwestern China. Growth, total NSC concentration and diurnal change of NSC were determined for the leaves and non-photosynthetic organs of three dominant species (Lannea coromandelica, Polyalthia cerasoides and Heteropogon contortus) throughout the growing season. Drought significantly reduced the growth of all the three species. Total NSC concentration averaged ~8.1%, varying with species, organ and sampling period, and did not significantly decrease under drought stress. By contrast, the diurnal change of NSC in these three species increased under drought stress. These results indicate that these three dominant species did not undergo carbon limitation. Thus, relative change in NSC is a more sensitive and effective indicator than carbon reserves in evaluation of plant carbon balance. These findings provide new insights for the understanding of carbon balance and the mechanisms of carbon starvation.

Developmental and reproductive performance of a specialist herbivore depend on seasonality of, and light conditions experienced by, the host plant.

Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.

The influence of exogenously applied 2,4-D and NAA on fruit drop reduction in pummelo cv. Thong Dee

ABSTRACTEffect of 2,4-D and naphthalene acetic acid (NAA) on fruit drop reduction in pummelo cv. Thong Dee was investigated in the pummelo growing areas of Nakhon Pathom province, Thailand. Five similar sized and aged of pummelo trees were selected to set up the experiment. Ten mature branches with the same size from each pummelo tree were randomly selected around the canopy for 2,4-D (20 and 40 mg L−1), NAA (20 and 40 mg L−1) application and control. All treatments were applied to selected pummelo branches 2 times at full bloom and 2 months after fruit set. The results showed that 20 mg L−1 NAA (14.84%) and 40 mg L−1 NAA (12.26%) gave significantly higher percent of fruit retention at 6 months after fruit set. However, leaf total nonstructural carbohydrate concentration analysis showed that 40 mg L−1 2,4-D (104.86 mg g−1) and 20 mg L−1 2,4-D (96.55 mg g−1) gave significantly higher total nonstructural carbohydrate than those in control (78.44 mg g−1). For fruit quality, 40 mg L−1 2,4-D and 20 mg L−1 2,4-D gave the highest peel weight with 435.55 and 358.57 g, respectively, and 40 mg L−1 2,4-D gave the highest peel thickness with 20.25 mm, while 20 mg L−1 NAA gave statistically higher total soluble solid than those in 20 mg L−1 2,4-D and 40 mg L−1 2,4-D. Therefore, 20 mg L−1 of NAA sprayed 2 times at full bloom and 2 month after fruit set effectively reduced fruit drop and increased percentage of fruit retention in pummelo cv. Thong Dee.

Determination of carbohydrate allocation patterns in water hyacinth to discover the potential physiological weak points in its life cycle

The seasonal allocation of carbohydrates in water hyacinth was evaluated to determine the physiological weak points in the life cycle of this plant in three large, moderately polluted freshwater canals north of the Nile Delta (Egypt). Monthly plant samples were divided into laminae, petioles, stolons, stem-bases and roots to determine the seasonal changes in water-soluble carbohydrates (WSC), starch and total non-structural carbohydrates (TNC) for each plant organ. Generally, water hyacinth allocated 2.2% of its total biomass to stolons, 4.5% to stem-bases, 19.0% to roots, 21.1% to laminae and 53.1% to petioles. The proportion of biomass allocated to the root system (stolons, stem-bases and roots) decreased from 38.5% in April to 17.2% in July, while that of the shoot system (laminae and petioles) increased from 61.5% to 82.8% during the same period. Stem-bases were found to contain the highest concentrations of WSC, starch and TNC throughout the water hyacinth’s life cycle. Starch represented the greatest part of the TNC pool, surpassing the concentration of WSC by 3.1- to 8.3-fold. The highest contents (g/m2) of WSC, starch and TNC were found in petioles. The period in the seasonal cycle when water hyacinth is expected to be most vulnerable to a control technique is when the carbohydrate contents are at the lowest. Based on the present study, this would be in April before complete mobilization of stored carbohydrates in the stem-bases and stolons have allowed expansion of the leaf material and the maximum growth rate.

Variation in carbohydrate and protein fractions, energy, digestibility and mineral concentrations in stover of sorghum cultivars

The nutritional attributes of stover from 11 sorghum cultivars ( SP 18005A x 220-2,3,6,7; PC-5; GGUB44 x SSG-59-3; ICSV-700; CSV-17; NRF-526; FM-1; SPV-1616; PVK-809; UPMC-503; and HC-308 ), selected on the basis of their diverse genetic backgrounds and use, were evaluated to aid in selecting parents superior in protein concentration and digestibility for use in sorghum breeding programs. Samples of stovers were collected after grain harvesting and analyzed. The CP concentrations in different cultivars differed (3.7‒6.7%; P<0.05) as did NDF, ADF, cellulose and lignin concentrations (P<0.05). Total carbohydrate, non-structural carbohydrate and structural carbohydrate concentrations differed (P<0.05) amongst cultivars as did carbohydrate fractions (C A , C B1 , C B2 , C C ; P<0.05). Protein fractions (P B1 , P B2 , P B3 and P C ) except P A differed (P<0.05). Concentrations of stover protein fractions P A and P B3 were lower than P B1 , P B2 and P C . Unavailable protein fraction P C was highest (P<0.05) in stover of SPV-1616 (36.8% CP) and lowest in ICSV-700 (20.4% CP). Concentrations of gross energy (GE), digestible energy (DE), metabolizable energy (ME) and total digestible nutrients (TDN) varied (P<0.05) and ICSV-700 had highest concentrations of DE, ME and TDN (2.60 kcal/g DM, 2.13 kcal/g DM and 59.0%, respectively). Energetic efficiency for maintenance (NE M ), lactation (NE L ) and growth (NE G ) differed (P<0.05) with ranges of 1.13‒1.42, 0.41‒0.70 and 0.95‒1.33 kcal/g DM, respectively. Values for estimated DM intake, estimated digestible DM and relative feed value for stovers also varied (P<0.05) with ranges of 1.76‒2.19%, 55.3‒61.4% and 75.4‒104.1%, respectively. In vitro dry matter digestibility was highest (P<0.05) for cultivars PVK-809 (55.7%) and ICSV-700 (54.3%). Macro- and micro-mineral concentrations also differed (P<0.05) across cultivar stovers. The wide genetic variability for nutritional attributes in stovers of sorghum cultivars indicates significant potential for improvement of stover quality through sorghum improvement programs, but care needs to be taken that grain and stover yields do not suffer. Keywords : Energy values, nutritive value, sorghum stover, yields. DOI: 10.17138/TGFT(6)42-52

Sex-specific responses of Populus deltoides to defoliation

There has been an increasing interest in understanding the differential effects of sexual dimorphism on plant stress responses. However, there is no clear pattern in the responses of the sexes to defoliation. In this study, the effects of different severity of artificial defoliation on biomass production, total nonstructural carbohydrate (NSC) concentration, and photosynthetic rate (&lt;em&gt;P&lt;/em&gt;&lt;sub&gt;N&lt;/sub&gt;) of male and female &lt;em&gt;Populus deltoides&lt;/em&gt; were examined. We used half and full defoliation to observe the differences between the sexes in three harvest dates (1 week, 4 weeks, and 8 weeks after treatments). We hypothesized that female and male &lt;em&gt;P. deltoides&lt;/em&gt; compared with an undefoliated control would have compensatory growth in response to defoliation treatments. Results showed that half and full defoliation reduced the growth of both sexes. Following half defoliation, root growth was reduced, especially in males, at T2 (4 weeks after defoliation) and T3 (8 weeks after defoliation), while males showed an increase in height increment under the half defoliation compared with the nondefoliation treatments. By contrast, females were more negatively affected by defoliation than males in terms of biomass after 8 weeks. One week after defoliation, &lt;em&gt;P&lt;/em&gt;&lt;sub&gt;N&lt;/sub&gt; increased significantly in females and males under half defoliation (+30%, +32%, respectively) and full defoliation (+58%, +56%, respectively). However, 8 weeks after defoliation, there was little difference in &lt;em&gt;P&lt;/em&gt;&lt;sub&gt;N&lt;/sub&gt; between defoliated and undefoliated female cuttings. Increases in stomatal conductance (g&lt;sub&gt;s&lt;/sub&gt;) and leaf nitrogen were observed under fully defoliated female and male cuttings. Moreover, males had less NSC concentrations following half defoliation compared with females. Our results indicate that leaf compensatory growth in male cuttings of &lt;em&gt;P. deltoides&lt;/em&gt; was maintained by obtaining greater photosynthetic capacity, higher leaf nitrogen, and lower NSC concentration following half and full defoliation. Our results highlight that females suffered from greater negative effects than did males following half defoliation, but under full defoliation, the differences between both sexes were subtle.

Ontogenetic stage, plant vigor and sex mediate herbivory loads in a dioecious understory herb

Plant-herbivore interactions can be mediated by plant apparency, defensive and nutritional quality traits that change through plant ontogeny, resulting in age-specific herbivory. In dioecious species, opposing allocation patterns in defense may lead to sex-biased herbivory. Here, we examine how onto stage and plant sex determine levels of herbivore damage in understory herb Mercurialis perennis under field conditions. We analyzed variation in plant size (height, total leaf area), physical (specific leaf area) and chemical (total phenolic and condensed tannins contents) defense, and nutritional quality (total water, soluble protein and nonstructural carbohydrate contents) during the shift from reproductive to post-reproductive stage. Furthermore, we explored correlations between the analyzed traits and levels of foliar damage. Post-reproductive plants had lower levels of chemical defense, and larger leaf area removed, in spite of having lower nutritive quality. Opposing patterns of intersexual differences were detected in protein and phenolic contents during reproductive stage, while in post-reproductive stage total leaf area was sexually dimorphic. Female-biased herbivory was apparent only after reproduction. Plant size parameters combined with condensed tannins content determined levels of foliar damage during post-reproductive stage, while the only trait covarying with herbivory in reproductive stage was total nonstructural carbohydrate content. Our results support claims of optimal defense theory – sensitive stage of reproduction was better defended. We conclude that different combinations of plant traits mediated interactions with herbivores in mature stages. Differences in reproductive allocation between the sexes may not immediately translate into different levels of damage, stressing the need for considering different ontogenetic stages when exploring sex bias in herbivory.

Post-drought hydraulic recovery is accompanied by non-structural carbohydrate depletion in the stem wood of Norway spruce saplings

Hydraulic failure and carbon starvation are recognized as main causes of drought-induced forest decline. As water transport and carbon dynamics are strictly interdependent, it is necessary to clarify how dehydration-rehydration cycles are affecting the relations between stem embolism and non-structural carbohydrates (NSC). This is particularly needed for conifers whose embolism repair capability is still controversial. Potted Norway spruce saplings underwent two drought-re-irrigation cycles of same intensity, but performed in two consecutive summers. During the second cycle, stem percent loss of hydraulic conductivity (PLC) and NSC content showed no carry-over effects from the previous drought, indicating complete long-term recovery. The second drought treatment induced moderate PLC (20%) and did not affect total NSCs content, while starch was converted to soluble sugars in the bark. After one week of re-irrigation, PLC recovered to pre-stress values (0%) and NSCs were depleted, only in the wood, by about 30%. Our data suggest that spruce can repair xylem embolism and that, when water is newly available, NSCs stored in xylem parenchyma can be mobilized over short term to sustain respiration and/or for processes involved in xylem transport restoration. This, however, might imply dependency on sapwood NSC reserves for survival, especially if frequent drought spells occur.