Defoliation Treatments Research Articles

Bovine serum albumin in saliva mediates grazing response in Leymus chinensis revealed by RNA sequencing.

BackgroundSheepgrass (Leymus chinensis) is an important perennial forage grass across the Eurasian Steppe and is adaptable to various environmental conditions, but little is known about its molecular mechanism responding to grazing and BSA deposition. Because it has a large genome, RNA sequencing is expensive and impractical except for the next-generation sequencing (NGS) technology.ResultsIn this study, NGS technology was employed to characterize de novo the transcriptome of sheepgrass after defoliation and grazing treatments and to identify differentially expressed genes (DEGs) responding to grazing and BSA deposition. We assembled more than 47 M high-quality reads into 120,426 contigs from seven sequenced libraries. Based on the assembled transcriptome, we detected 2,002 DEGs responding to BSA deposition during grazing. Enrichment analysis of Gene ontology (GO), EuKaryotic Orthologous Groups (KOG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways revealed that the effects of grazing and BSA deposition involved more apoptosis and cell oxidative changes compared to defoliation. Analysis of DNA fragments, cell oxidative factors and the lengths of leaf scars after grazing provided physiological and morphological evidence that BSA deposition during grazing alters the oxidative and apoptotic status of cells.ConclusionsThis research greatly enriches sheepgrass transcriptome resources and grazing-stress-related genes, helping us to better understand the molecular mechanism of grazing in sheepgrass. The grazing-stress-related genes and pathways will be a valuable resource for further gene-phenotype studies.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1126) contains supplementary material, which is available to authorized users.

The Simulated Effect of Defoliation in the Growth of the Eucalyptus grandis

In recent decades, Brazil has been standing out as one of the major world producers of pulp and paper. The industrial sector defined as pulp and paper currently consists of approximately 222 companies with activities in 539 municipalities, which are distributed throughout the national territory. The pulp and paper industry is divided in the forest and industrial sectors. In the forest sector a major problem in the production process is the control of pests that occur in the culture, reducing the productive capacity of the forest which directly affects the industrial sector. Noteworthy are the defoliating insects such as leaf-cutter ants, Lepidoptera and beetles, which cause great damage. Studies assessing defoliation caused by these insects are important tools that can aid programs of integrated pest management to increase productivity and reduce production costs. This work aimed to evaluate the effect of different levels of simulated defoliation on the growth of Eucalyptus grandis trees, with six months of age. The experiment was conducted in a randomized block design with five replications and six treatments, totaling 3,000 trees. Defoliation levels of 100 %; 50 % and 75 % of the upper canopy were analysed, as well as 50 % and 75 % of the basal part of the crown, and the top 25 % of the trees. The control was 0 % defoliation. The results showed that only total defoliation can cause a reduction in diameter and height growth. These trees lost 10.88 mm and 0.72 m in their diameter and height, respectively. At 240 days after injury, in spite of total defoliation, the trees already, presented height identical to those of trees which had undergone 50 to 75 % defoliation. The volume loss in this period, for the totally defoliated trees was 35 %. This loss will be reduced to 13 % when extrapolated for a rotation of 7 years. The results may be used in the monitoring program of leaf-cutting ants to reduce to the cost of chemical control of these insects on Eucalyptus in Brazil, and consequently improve the environmental quality of planted forests, raising their productivity and quality.

Effects of artificial defoliation on growth and biomass accumulation in short-rotation sweetgum (Liquidambar styraciflua) in North Carolina.

Sweetgum, Liquidambar styraciflua L. (Hamamelidales: Hamamelidaceae), is a species of interest for short-rotation plantation forestry in the southeastern United States. Despite its high levels of resistance to many native insects and pathogens, the species is susceptible to generalist defoliators during outbreak epidemics. The objective of this field study was to evaluate the potential impact of defoliation on sweetgum growth and productivity within the context of an operational plantation. Over three growing seasons, trees were subjected to artificial defoliation treatments of various intensity (control = 0% defoliation; low intensity = 33% defoliation; moderate intensity = 67% defoliation; high intensity = 99% defoliation) and frequency (not defoliated; defoliated once in April of the first growing season; defoliated twice, once in April of the first growing season and again in April of the second growing season). The responses of stem height, stem diameter, stem volume, crown volume, total biomass accumulation, and branch growth were measured in November of each growing season. At the end of the first growing season, when trees had received single defoliations, significant reductions in all growth traits followed the most severe (99%) defoliation treatment only. After the second and third growing seasons, when trees had received one or two defoliations of varying intensity, stem diameter and volume and total tree biomass were reduced significantly by 67 and 99% defoliation, while reductions in stem height and crown volume followed the 99% treatment only. All growth traits other than crown volume were reduced significantly by two defoliations but not one defoliation. Results indicate that sweetgum is highly resilient to single defoliations of low, moderate, and high intensity. However, during the three-year period of the study, repeated high-intensity defoliation caused significant reductions in growth and productivity that could have lasting impacts on yield throughout a harvest rotation.

Hydraulic adjustments in aspen (Populus tremuloides) seedlings following defoliation involve root and leaf aquaporins

Changes in root and leaf hydraulic properties and stimulation of transpiration rates that were initially triggered by defoliation were accompanied by corresponding changes in leaf and root aquaporin expression. Aspen (Populus tremuloides) seedlings were subjected to defoliation treatments by removing 50, 75 % or all of the leaves. Root hydraulic conductivity (Lpr) was sharply reduced in plants defoliated for 1 day and 1 week. The decrease in L pr could not be prevented by stem girdling and it was accompanied in one-day-defoliated plants by a large decrease in the root expression of PIP1,2 aquaporin and an over twofold decrease in hydraulic conductivity of root cortical cells (L pc). Contrary to L pr and L pc, 50 and 75 % defoliation treatments profoundly increased leaf lamina conductance (K lam) after 1 day and this increase was similar in magnitude for both defoliation treatments. Transpiration rates (E) rapidly declined after the removal of 75 % of leaves. However, E increased by over twofold in defoliated plants after 1 day and the increases in E and K lam were accompanied by five- and tenfold increases in the leaf expression of PIP2;4 in 50 and 75 % defoliation treatments, respectively. Defoliation treatments also stimulated net photosynthesis after 1 day and 3 weeks, although the increase was not as high as E. Leaf water potentials remained relatively stable following defoliation with the exception of a small decrease 1 day after defoliation which suggests that root water transport did not initially keep pace with the increased transpirational water loss. The results demonstrate the importance of root and leaf hydraulic properties in plant responses to defoliation and point to the involvement of PIP aquaporins in the early events following the loss of leaves.

Effect of defoliation treatment on Mimosa pigra L. seedling survivability and resilience

Current advancements in the study of the theoretical basis of species interactions are helping scientists understand the basic parameters governing the dynamics of the interactions between generalist herbivores and their target plants. In practice, however, both inter- and intra-specific interactions between plants (as well as between herbivores and plants) within multispecies systems that are under the influence of interrelated biotic and abiotic variables are difficult to predict. Here, we discuss our findings on the effect of simulated herbivory on Mimosa pigra L. leaves on seedling survivability. In Malaysia, M. pigra, a semi-aquatic invasive plant introduced from the South American region, is already creating an ecological problem, especially in wetland habitats. To better understand the impact of herbivores on the M. pigra population, a simulated experiment of the herbivory effect on Mimosa seedlings was conducted. This experiment combined two treatments of simulated herbivory on the leaves of established Mimosa seedlings, that is, a two-level intensity treatment (50 and 100 % defoliation) and a seven-level frequency treatment (one to seven defoliations). The data suggest that Mimosa is highly resilient against herbivory. This plant was able to compensate for repeated losses, thus suggesting that the introduction of herbivores in an effort to totally eradicate the Mimosa population is unlikely to be successful.

Effects of defoliation and water restriction on total phenols and antioxidant activities in grapes during ripening

<p style="text-align: justify;"><strong>Aim</strong>: To compare the effect of water restriction and defoliation on the phenol contents and oxidant and antioxidant activities of Tempranillo grapes grown in the region of Extremadura, Spain.</p><p style="text-align: justify;"><strong>Methods and results</strong>: The results showed that at harvest, the water restriction treatment altered total foliar area, pH, and total soluble solid (TSS) and phenol contents but not polyphenol oxidase (PPO) and superoxide dismutase (SOD) activities. By contrast, the defoliation treatment did not affect TSS and pH, however, titratable acidity and phenol compounds were enhanced and PPO and SOD activities were decreased. Moreover, defoliation resulted in advanced grape ripening and reduced total foliar area. </p><p style="text-align: justify;"><strong>Conclusion</strong>: At harvest, water restriction led to alterations in the levels of peroxidation and peroxidase (POX) activity, without any effect on the other parameters. Defoliation induced a lowering of PPO and SOD activities and an increase in phenol content.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Given the environmental characteristics of the Extremadura region, defoliation may be suitable and efficient for regulating Tempranillo grape PPO activity, which is œnologically relevant since it could lead to lower levels of phenol oxidation and hence prevent wine discolouration.</p>

Inheritance of the responses to a defoliation treatment affecting cold tolerance in maize

Previous studies revealed that defoliation can bring about differential responses in maize (Zea mays L.) genotypes for cold tolerance. This research was conducted to study the inheritance of the responses to defoliation for germination at low temperature and for seedling traits in early-sown field trials. Six inbred lines were crossed according to the complete diallel scheme, thus producing 36 genotypes. At milk ripening stage, half of the plants of each genotype were completely defoliated (D) whereas the other half were not (ND). Two experiments were conducted for two years, one in the germinator and one in the field. The response to defoliation was evaluated as (D–ND). Across the two years, the D treatment caused an average kernel weight decrease of −56 mg (−23.1 % as referred to ND), an increase of 2.3 % for germination at 9 °C (G9) and a reduction of −0.3 d for the average time of germination (ATG); in contrast, the defoliation effect was negligible for germination at 25 °C. In the field, the defoliation effects were more notable in the first (colder) year and led to an increase of 2.0 % for field emergence (FE) and to a decrease of −2.7 g for seedling fresh weight (SFW). The genotypic variation for the (D–ND) response was significant for additive, dominance and reciprocal effects for G9, ATG, FE and SFW. There was consistency among lines across traits for additive effects, with Lo1016 and Os420 showing the best and the worst effect, respectively.

Yield Response of Needle-and-Thread and Threadleaf Sedge to Moisture Regime and Spring and Fall Defoliation

Little information is available to help managers of cool-season dominated semiarid rangelands determine when to begin and end grazing in the spring and fall. Therefore, we evaluated the effects of clipping spring and fall growth on subsequent-year yield of needle-and-thread (Hesperostipa comata [Trin. & Rupr.] Barkworth) and threadleaf sedge (Carex filifolia Nutt.) (USDA-NRCS 2012) using a randomized complete block, split-plot experimental design with fall moisture regimes (ambient or supplemental water) applied to main plots and defoliation treatments applied to subplots. Two combinations of spring defoliation, one for each fall moisture regime, were composed of a factorial array of three spring clipping dates (early May, late May, mid-June) and three levels of defoliation (0%, 40%, 80%). A third combination of treatments was composed of the supplemental water regime and an array of a single spring clipping date (late May), a single fall clipping date (late September, after regrowth), and three levels of defoliation (0%, 40%, 80%) in the same year. Ambient fall moisture was low, leading to continued senescence of needle-and-thread and threadleaf sedge, whereas the application of 10 cm of supplemental water in mid-August stimulated fall growth. The study was replicated with two sets of main plots at four sites in consecutive years, 2002 and 2003. Yield data were collected in mid-June of the year following treatment. Subsequent-year yield of needle-and-thread was not affected by defoliation under average plant-year precipitation conditions (2003) (P > 0.05); however, it was reduced following heavy (80%) late spring (late May or June) defoliation during a drought year (2002) (P > 0.05). Subsequent-year yield of threadleaf sedge was not affected by defoliation in either year (P > 0.05). Because it is difficult to predict when drought will occur, avoiding heavy late-spring grazing in needle-and-thread–dominated pastures in consecutive years would be prudent.

Effect of herbivory on the growth and photosynthesis of replanted Calligonum caput-medusae saplings in an infertile arid desert

Replanted Calligonum caput-medusae saplings in the Tarim River watershed face short-term and frequent herbivory by goats, which can result in either growth inhibition or stimulation. The effects of herbivory on shrub saplings are unclear. We simulated herbivory with clipping to test two hypotheses. We hypothesized that (1) moderate herbivory may positively affect replanted shrub saplings due to overcompensatory growth and compensatory photosynthesis and that (2) high amounts of defoliation may change water availability and impair photosynthesis and growth of saplings. We applied four defoliation treatments (0, 30, 50, and 70 %) to 2-year-old C. caput-medusae saplings to test the effects of herbivory. Moderately defoliated (~30 %) saplings grew faster and had higher photosynthetic performance than controls; however, defoliation of 50 % or more reduced growth due to undercompensatory photosynthesis and reduced water availability. Non-photochemical quenching by thermal dissipation provided photoprotection when absorbed light energy used in PSII photochemistry was inhibited, reducing excess excitation energy and allowing saplings with high amounts of defoliation to maintain adequate photosystem functioning. This suggests that moderate herbivory of replanted shrubs used as forage in arid ecological restoration projects is feasible, but that uncontrolled grazing should be forbidden.

Responses of Maize (SC704) Yield and Yield Components to Source Restriction

Understanding the relationship between sink and source in maize is of prime importance in maize growing regions. In this study, a field experiment was carried out during spring and summer 2007 in the experimental field of the College of Agriculture, Shiraz University, to examine the effects of source restriction (defoliation) on sink size (yield and its components) of SC704 maize hybrid. A factorial arrangement in a randomized complete block design with four replications was used. Treatments composed of four stages of source restriction including defoliation at half-silking and 3 consecutive 10 day intervals, as well as three defoliation intensities (zero, half and all leaf removal). It was found that delay in source limitation was associated with a lower mean kernel weight achievement. The highest mean kernel weight was attained in defoliation at half- silking (208.14 g), which also resulted in the lowest grain yield reduction, compared to no defoliation treatment. Increase in defoliation intensity was associated with a decrease in grain yield; however, delay in defoliation after mid- silking had no significant effect on grain yield. It was concluded that the grain yield of SC704 maize hybrid was more sensitive to source limitation (i.e. defoliation) intensity than defoliation time.

Contrasting impacts of defoliation on root colonization by arbuscular mycorrhizal and dark septate endophytic fungi of Medicago sativa

Individual plants typically interact with multiple mutualists and enemies simultaneously. Plant roots encounter both arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungi, while the leaves are exposed to herbivores. AMF are usually beneficial symbionts, while the functional role of DSE is largely unknown. Leaf herbivory may have a negative effect on root symbiotic fungi due to decreased carbon availability. However, evidence for this is ambiguous and no inoculation-based experiment on joint effects of herbivory on AM and DSE has been done to date. We investigated how artificial defoliation impacts root colonization by AM (Glomus intraradices) and DSE (Phialocephala fortinii) fungi and growth of Medicago sativa host in a factorial laboratory experiment. Defoliation affected fungi differentially, causing a decrease in arbuscular colonization and a slight increase in DSE-type colonization. However, the presence of one fungal species had no effect on colonization by the other or on plant growth. Defoliation reduced plant biomass, with this effect independent of the fungal treatments. Inoculation by either fungal species reduced root/shoot ratios, with this effect independent of the defoliation treatments. These results suggest AM colonization is limited by host carbon availability, while DSE may benefit from root dieback or exudation associated with defoliation. Reductions in root allocation associated with fungal inoculation combined with a lack of effect of fungi on plant biomass suggest DSE and AMF may be functional equivalent to the plant within this study. Combined, our results indicate different controls of colonization, but no apparent functional consequences between AM and DSE association in plant roots in this experimental setup.

Cues from a specialist herbivore increase tolerance to defoliation in tomato

Summary Recent studies have shown that herbivore cues trigger rapid shifts in primary metabolism and resource allocation within a plant. This has been suggested to be an induced mechanism of tolerance to defoliation but there is little evidence supporting this. Here, we investigated, using a cultivar of tomato (Solanum lycopersicum), whether prior herbivore damage confers plants an advantage in terms of increased growth and initial flower production following defoliation. Plants were mechanically wounded and treated with either regurgitant of the specialist Manduca sexta, deionized water or received no damage for five consecutive days. Chlorophyll content, plant growth and biomass allocation were measured during the 5‐day damage period. After the damage treatments, all leaves were removed to simulate defoliation in the three treatment groups, and regrowth capacity was followed until flowering. The number of regrown leaves, the initial number of flowers and biomass production and allocation were quantified at harvest. During the 5‐day damage period, plants treated with M. sexta regurgitant grew less in height than undamaged plants (but had thicker stems). Chlorophyll content also decreased sharply in these plants. However, regurgitant‐treated plants recovered more quickly from the defoliation treatment, producing more new leaves compared with undamaged and mechanically damaged treatments. Our results support the hypothesis that induced changes in resource allocation in response to specialist herbivores results in increased regrowth ability and may be adaptive in the event of severe defoliation. Future studies on wild plants could help inform the evolutionary significance of this response.

The effects of defoliation on carbon allocation: can carbon limitation reduce growth in favour of storage?

There is no consensus about how stresses such as low water availability and temperature limit tree growth. Sink limitation to growth and survival is often inferred if a given stress does not cause non-structural carbohydrate (NSC) concentrations or levels to decline along with growth. However, trees may actively maintain or increase NSC levels under moderate carbon stress, making the pattern of reduced growth and increased NSCs compatible with carbon limitation. To test this possibility, we used full and half defoliation to impose severe and moderate carbon limitation on 2-year-old Quercus velutina Lam. saplings grown in a common garden. Saplings were harvested at either 3 weeks or 4 months after treatments were applied, representing short- and longer-term effects on woody growth and NSC levels. Both defoliation treatments maintained a lower total leaf area than controls throughout the experiment with no evidence of photosynthetic up-regulation, and resulted in a similar total biomass reduction. While fully defoliated saplings had lower starch levels than controls in the short term, half defoliated saplings maintained control starch levels in both the short and longer term. In the longer term, fully defoliated saplings had the greatest starch concentration increment, allowing them to recover to near-control starch levels. Furthermore, between the two harvest dates, fully and half defoliated saplings allocated a greater proportion of new biomass to starch than did controls. The maintenance of control starch levels in half defoliated saplings indicates that these trees actively store a substantial amount of carbon before growth is carbon saturated. In addition, the allocation shift favouring storage in defoliated saplings is consistent with the hypothesis that, as an adaptation to increasing carbon stress, trees can prioritize carbon reserve formation at the expense of growth. Our results suggest that as carbon limitation increases, reduced growth is not necessarily accompanied by a decline in NSC concentrations. Therefore, a lack of NSC decline may not be evidence that reduced tree growth under cold or water stress is caused by sink limitation.

Spring Clipping, Fire, and Simulated Increased Atmospheric Nitrogen Deposition Effects on Tallgrass Prairie Vegetation

Defoliation aimed at introduced cool-season grasses, which uses similar resources of native grasses, could substantially reduce their competitiveness and improve the quality of the northern tallgrass prairie. The objective was to evaluate the use of early season clipping and fire in conjunction with simulated increased levels of atmospheric nitrogen deposition on foliar canopy cover of tallgrass prairie vegetation. This study was conducted from 2009 to 2012 at two locations in eastern South Dakota. Small plots arranged in a split-plot treatment design were randomized in four complete blocks on a warm-season grass interseeded and a native prairie site in east-central South Dakota. The whole plot consisted of seven treatments: annual clip, biennial clip, triennial clip, annual fire, biennial fire, triennial fire, and undefoliated control. The clip plots consisted of weekly clipping in May to simulate heavy grazing. Fire was applied in late April or early May. The subplot consisted of nitrogen applied at 0 or 15 kg N · ha−1 in early June. All treatments were initially applied in 2009. Biennial and triennial treatments were reapplied in 2011 and 2012, respectively. Canopy cover of species/major plant functional groups was estimated in late August/early September. Annual clipping was just as effective as annual fire in increasing native warm-season grass and decreasing introduced cool-season grass cover. Annual defoliation resulted in greater native warm-season grass cover, less introduced cool-season grass cover, and less native cool-season grass cover than biennial or triennial defoliation applications. Low levels of nitrogen did not affect native warm-season grass or introduced cool-season cover for any of the defoliation treatments, but it increased introduced cool-season grass cover in the undefoliated control at the native prairie site. This study supports the hypothesis that appropriately applied management results in consistent desired outcomes regardless of increased simulated atmospheric nitrogen depositions.

조기낙엽에 따른 참다래(골드러쉬) 무착과 유목 액아의 발아와 착화

BACKGROUND: Kiwifruit, which was introduced to Korea in late 1970s, is a warm-temperate fruit tree, whose leaves are easily damaged by wind because of their large size. To produce high quality fruits, efficient windbreak is necessary to protect leaves until harvest. In Korea, typhoons from July onwards usually influence the production of kiwifruit. Damages from typhoons include low fruit quality in the current year and low flowering ratio the following year. This study was conducted to investigate the effect of early defoliation of kiwifruit vines from July to October on the regrowth of shoot axillary buds the current year and bud break and flowering the following year. METHODS AND RESULTS: Scions of kiwifruit cultivar 'Goldrush' were veneer grafted onto five-year-old Actinidia deliciosa rootstocks, planted in Wagner pots (13L) and grown in a rain shelter. Kiwifruit leaves in the proximity of leaf stalk were cut by lopping shears to simulate mechanical damage from typhoon since only leaf stalks were left when kiwifruit vines were damaged by typhoons. Kiwifruit vines were defoliated from July 15 to October 14 with one monthintervals and degrees of defoliation were 0, 25, 50, 75 and 100%. All experiments were conducted in the rain shelter and replicated at least five times. Defoliation in July 15 resulted in a high regrowth ratio of 20-40% regardless of degree of defoliation but that in August 16 showed only 5.8% of regrowth ratio in the no defoliation treatment; however, more than 25% of defoliation in August 16 showed 17-23% of regrowth ratio. In September 15, regrowth ratio decreased further to less than 10% in all treatments and no regrowth was observed in October 14. Percent bud break of all defoliation treatments were not significant in comparison to 64.7% in no defoliation except for 42.1% and 42.9% in 100% defoliation in July 15 and August 16, respectively. Floral shoot in the no defoliation treatment was 70.2% and defoliation of 50% or less resulted in the same or increased floral shoot ratio in July 15, August 16, and September 15; however, defoliation in October 14 showed no difference in all treatments. In flower number per floral shoot, 2-3 flowers appeared in no defoliation and only 1 flower was observed when the vines were defoliated more than 50% in July 15 and September 15. In October 14, contrary to the floral shoot ratio, flower number decreased with increased defoliation. CONCLUSION(S): Therefore, it is suggested that dormancy of 'Goldrush' axillary buds, was started in August and completed in October. The effect of defoliation on bud break of axillary buds the following year was insignificant, except for 100% defoliation in July 15 and August 16. From July 15 to September 15, floral bud ratio was significantly reduced when more than 50% of leaves were defoliated compared to no defoliation. Also, the number of flowers per flower-bearing shoot the following year decreased by less than 50% when compared to no defoliation, and this decrease was more prominent in September 15 than July 15 and August 16.

갈색무늬병의 시기별 이병 및 낙엽 정도가 '후지'/M.9 사과나무의 과실품질 및 신초생장에 미치는 영향

본 조사연구는 갈색무늬병(Diplocarpon mali Harada et Sawamura)의 시기별 이병 및 낙엽 정도가 '후지'/M.9 사과나무의 신초생장과 과실품질에 미치는 영향을 조사하고자 실시하였다. 2009년 군위지역에서의 갈색무늬병 발생은 7월 중에 시작되었고, 10월 말에 10% 정도 낙엽이 되었다. 2010년에는 갈색무늬병 발생은 6월 초에 시작하였다. 낙엽률은 9월 말에 20%이었고, 10월 말에 50%에 도달하였다. 2010년 정단신초의 이차생장량은 2009년보다 약 3배 더 높았다. 2009년 과실 성숙기 동안의 가용성 고형물 함량과 착색 정도(Hunter a value)는 각각 <TEX>$13.8^{\circ}Brix$</TEX>, 16.2까지 올라갔다. 2010년 과실 성숙기 동안의 가용성 고형물 함량은 10월초 이후로 <TEX>$12.1-12.6^{\circ}Brix$</TEX> 범위에 머물렀고, 착색은 낙엽이 20%된 9월 말 이후에 높아지기 시작하였다. 낙엽 정도에 따른 과실품질에 있어, 10월 말 과대지의 낙엽율이 30% 이상이 되면 착색도가 감소되었고, 낙엽율이 50% 이상이 되면 과중과 가용성 고형물 함량이 감소되었다. 10월 말 30% 이상 낙엽구의 과실 종경과 횡경은 30% 미만 낙엽구과 비교해 볼 때, 8월 중순부터 감소되기 시작하였다. 2010년 8월말 과대지에서 이차생장한 부위 잎의 광합성 속도는 기존의 과대지 중간 부위의 잎과 비슷하였다. 그러나 과실의 크기와 가용성 고형물 함량은 과대지의 이차생장한 부위 잎의 광합성 활동에 영향을 받지 않았다. This study investigated the influence of seasonal incidence and defoliation degree caused by Marssonina blotch (Diplocarpon mali Harada et Sawamura) on shoot growth and fruit quality of 'Fuji'/M.9 apple tree. The occurrence of marssonina blotch in Gunwi region was observed from the mid of July 2009, and percentage of defoliation was about 10% in the end of October. In 2010, that started in the early of June. By the end of September, percentage of defoliation was 20% and it reached 50% in late October. Secondary growth of terminal shoot in 2010 was three times as much as that in 2009. In 2009, the soluble solid contents and the red color (hunter a value) during fruit maturation increased to <TEX>$13.8^{\circ}Brix$</TEX> and 16.2, respectively. In 2010, the soluble solid content during fruit maturation remained in the <TEX>$12.1-12.6^{\circ}Brix$</TEX> range after early October, and the red color began to increase after the end of September when the percentage of defoliation was 20%. As for fruit quality by defoliation degree, the red color decreased when defoliation percentage of bourse shoot at the end of October was more than 30%. Fruit weight and soluble solids also decreased when defoliation percentage was more than 50%. Fruit length and diameter of over 30% defoliation treatments begun to decrease after the middle of August, compared with those of under 30% defoliation treatment. Photosynthetic rate of the leaves that was located at the secondary growth of bourse shoot was similar to that of leaves which was located at the middle of bourse shoot. However, the size and the soluble solid content of fruit were not affected by photosynthesis activities of bourse shoot leaves which was develop in the secondary shoot growth.

リュウキュウコクタン（Diospyros ferrea）の環状剥皮、摘葉処理が繁殖資源の転流とC/N比に及ぼす影響

リュウキュウコクタン（Diospyros ferrea）の環状剥皮、摘葉処理が繁殖資源の転流とC/N比に及ぼす影響

Impact of defoliation on the regrowth capacity and the shoot metabolite profile of Plantago lanceolata L.

After defoliation challenges, plants should invest their resources in a way that maximizes their fitness, which may lead to trade-offs in investment in physiological versus chemical traits. Thereby, the regrowth capacity of plants may highly depend on the type and the severity of defoliation. In the present study, we investigated the phenotypic plasticity of Plantago lanceolata L. in response to different defoliation events in a comprehensive way, measuring various traits. This herbaceous species grows on ruderal sites and typically suffers from repeated substantial losses of shoot biomass due to mowing and/or herbivory during the growing season. To study treatment-specific effects of defoliation on resource allocation and induction of defence responses, plants were exposed either to (repeated) mechanical clipping or to herbivory by the generalist Grammia incorrupta (Lepidoptera). Next to regrowth and physiological leaf traits such as the water content, the specific leaf area and C/N ratios of these plants, primary and secondary metabolites in leaves were analyzed with a metabolite profiling approach using gas chromatography coupled with mass spectrometry. The different defoliation treatments strongly affected the regrowth capacity of clipped and herbivore-treated plants, leading to additive changes in physiological leaf traits. As a response to the defoliation treatments, clipped and herbivore-treated plants reduced mainly carbon-based primary metabolites such as sorbitol, and glucose, suggesting that the different defoliation challenges similarly limited the ability of carbon fixation. Yet, only in response to herbivory but not to clipping, plants induced defence compounds, which indicates the importance of treatment-specific responses despite severe resource limitations. Overall, the different responses to defoliation by clipping and herbivory may reflect allocation constraints and/or adaptive plasticity.

SOURCE-SINK MANIPULATION EFFECTS ON MAIZE KERNEL QUALITY

Evaluation of source or sink limitations on maize (Zea mays L.) yield and yield components is important for the rational design of agricultural practices as well as breeding strategies. There is little information on how the source or sink limitations during the effective grain-filling period affect final kernel quality. The objective of this study was to evaluate the effect of source/sink manipulation in different times after mid-silking stage on kernel weight (KW), kernel number per square meter (KN m−2), kernel protein and oil of different maize hybrids. Field experiments were conducted at the experimental field of College of Agriculture, Shiraz University, Shiraz, Iran, located at Bajgah (52° 35′ N and 39° 4′ E and 1810 m above sea level, asl) during the 2008 and 2009 growing seasons. The treatments included three hybrids and defoliation that were arranged in the main, and subplots, respectively. Leaves removal treatments were imposed when plants were at the mid-silking stage. Silking was taken as the time when 50% of the plants in a row presented visible silks. Defoliations included control, 50% of defoliation at 25 (early defoliation), and 35 (late defoliation) days after silking (defoliation treatments were applied to all plants of each plot). The experiments were conducted in randomized complete block (RCB) design with three replications and the treatments in a split-plot arrangement. Early defoliation greatly reduced kernel growth rate and grain filling period, resulting in lower mean kernel weight. Defoliation treatments modified KN m−2 and kernel number per ear (KNPE) and variations in these components affected protein and oil content. Decreased source size by defoliation decreased kernel protein content dramatically with no significant change in oil content. Differences among treatments appeared to be related only to the post-flowering source/sink ratio. Therefore, to improve protein yield in maize, hybrids and agronomic practices should aim to increase the post-flowering source/sink ratio.

Influence of mechanical postveraison leaf removal apical to the cluster zone on delay of fruit ripening in Sangiovese (Vitis vinifera L.) grapevines

Background and Aims Postveraison limitation of canopy photosynthesis delays grape berry ripening and reduces sugar accumulation, thus lowering the alcohol content of the subsequent wines. This study was designed to evaluate whether similar results could be obtained by defoliation apical to the bunch zone using a leaf-plucking machine when berry sugar content was approximately 16–17°Brix. Methods and Results In 2011 and 2012, defoliation treatments were applied postveraison to cv. Sangiovese vines (D) on either side of each row using a mechanical leaf remover, and these D vines were compared to a nondefoliated control (C). The machine removed 35% of the leaves on the vine and created a 50-cm vertical window without leaves above the bunch area, but retained a few leaves at the canopy apex (about 0.50 m2/vine). In both years, leaf removal reduced the rate of berry sugar accumulation and led to a 1.2 lower harvest °Brix and consequently, a lower wine alcohol (−0.6%) content in D relative to that of C vines. In 2012, sugar content of D vines, monitored in a group of vines that was not harvested, had recovered to that of C vines 2 weeks after harvest. The concentration of total phenolic compounds in the grapes, the chemical and chromatic characteristics of the wines and the replenishment of soluble sugars, starch and total nitrogen in the canes and roots were similar in the D and C vines. Conclusion To achieve an effective delay in sugar accumulation in the berries, leaves should be removed at 16–17°Brix, and at least 30–35% of vine leaf area should be removed. Significance of the Study Mechanical removal of leaves postveraison above the bunch zone of Sangiovese can be an easy and economically viable technique for delaying sugar accumulation in the berries and for limiting the alcohol content of wines with no negative impact on desirable composition of either berries or wines.