Intra- specific variation in response of Jatropha (Jatropha curcas L.) to elevated CO2 conditions

Twenty genotypes of Jatropha collected from diverse eco-geographic regions from the states of Chhattisgarh (3), Andhra Pradesh (12), Rajasthan (4) and Uttarakhand (1) of India were subjected to elevated CO₂ conditions. All the genotypes showed significant difference (p < 0.05 and 0.01) in the phenotypic traits in both the environments (elevated and ambient) and genotype x environment interaction. Among the physiological traits recorded, maximum photosynthetic rate was observed in IC565048 (48.8 μmol m⁻² s⁻¹) under ambient controlled conditions while under elevated conditions maximum photosynthetic rate was observed in IC544678 (41.3 μmol m⁻² s⁻¹), and there was no significant difference in the genotype x environment interaction. Stomatal conductance (Gs) emerged as the key factor as it recorded significant difference among the genotypes, between the environments and also genotype x environment interaction. The Gs and transpiration (E) recorded a significant decline in the genotypes under the elevated CO₂ condition over the ambient control. Under elevated CO₂ conditions, the minimum values recorded for Gs and E were 0.03 mmol m⁻² s⁻¹ and 0.59 mmol m⁻² s⁻¹ respectively in accession IC565039, while the maximum values for Gs and E were 1.8 mmol m⁻² s⁻¹ and 11.5 mmol m⁻² s⁻¹ as recorded in accession IC544678. The study resulted in the identification of potential climate ready genotypes viz. IC471314, IC544654, IC541634, IC544313, and IC471333 for future use.     

Genetic associations, variability and diversity in seed characters, growth, reproductive phenology and yield in Jatropha curcas (L.) accessions

A thorough and extensive wild germplasm exploration survey was undertaken and 32 high yielding candidate plus trees (CPTs) of Jatropha curcas from different locations from a latitudinal and longitudinal spread between 12°41′ and 22°′E longitude and 77° and 84°40′N latitude covering 11 locations in an area spread of 150,000 km² was collected for evaluating genetic association, and variability in seed and growth characters. Significant trait differences were observed in all the seed characters viz., seed morphology and oil content as were observed in growth characters viz., plant height, and female to male flower ratio and seed yield in the progeny trial. Broad sense heritability was high in general and exceeded 80% for all the seed traits studied. Female to male flower ratio showed near to 100% heritability followed by yield (83.61) and plant height (87.73). The path analysis revealed that female to male flower ratio had highest positive direct relationship with seed yield (0.789), followed by number of branches (0.612) and number of days from fruiting to maturity (0.431). Negative indirect effects were seen in number of days from flowering to fruiting which indirectly and negatively influenced yield through plant height and number of branches. Hierarchical clustering by Ward’s minimum variance cluster analysis showed phylogeographic patterns of genetic diversity. K-means clustering revealed that trees from different geographic regions were grouped together in a cluster and as were trees from the same geographical area placed in different clusters suggesting that geographical diversity did not go hand in hand with genetic diversity. In addition clustering identified promising accession with favourable traits for future establishment of elite seedling seed orchard and clonal seed orchard for varietal and hybridization programmes. For Genetical statistics please contact Arun K. Shanker (e-mail: arunshank@gmail.com).     

Factors influencing direct shoot regeneration from mature leaves of Jatropha curcas, an important biofuel plant

In order to establish a highly efficient and sustainable regeneration system, we systematically researched the key factors affecting direct shoot regeneration from Jatropha curcas leaves that were collected from Hainan (HN1-1), Lijiang (LJ3-1), and Yuxi (YX2-12) provinces in China. The L₉(3⁴) orthogonal test of thidiazuron (TDZ), kinetin (Kn), and gibberellic acid (GA₃) were studied, and the explant type, growth age, and cultivar of leaves were subsequently investigated. Simultaneously, the combinations of plant growth regulators (PGRs) promoting shoot bud proliferation, elongation, and root establishment were examined. The results showed that the best medium for shoot bud induction was Murashige and Skoog (MS) medium supplemented with 1.0 mg/L TDZ, 0.5 mg/L Kn, and 0.5 mg/L GA₃. TDZ was the key PGR, while Kn and GA₃ played an important role in shoot bud elongation and the number of shoots per leaf disk, respectively. The induced shoot buds proliferated and readily elongated in MS medium with 0.3 mg/L 6-benzylaminopurine and 0.01 mg/L indole-3-butyric acid (IBA) and established roots in half-strength MS medium supplemented with 2.0 mg/L IBA. Using the previously described methods, the third to fifth leaves were found to be the best explant source for shoot bud induction, with a high induction rate, large shoot numbers per disk, excellent proliferation, and consistent rooting. With the use of this regeneration system, the shoot bud induction rate increased from the reported rate of 53.5% to more than 90% using different explants and cultivars, and the shoot number per leaf disk (shoot length?≥?0.5 cm) increased from 1.6 to 3.5. Thus, this optimized regeneration system will effectively promote the propagation and genetic transformation of J. curcas.     

The effect of plant material grown under elevated CO2 on soil respiratory activity

The biodegradability of aerial material from a C4 plant, sorghum grown under ambient (345 µmol mol^–1) and elevated (700 µmol mol^–1) atmospheric CO₂ concentrations were compared by measuring soil respiratory activity. Initial daily respiratory activity (measured over 10 h per day) increased four fold from 110 to 440 cm³ CO₂ 100g dry weight soil^–1 in soils amended with sorghum grown under either elevated or ambient CO₂. Although soil respiratory activity decreased over the following 30 days, respiration remained significantly higher (t-test;p>0.05) in soils amended with sorghum grown under elevated CO₂ concentrations. Analysis of the plant material revealed no significant differences in C:N ratios between sorghum grown under elevated or ambient CO₂. The reason for the differences in soil respiratory activity have yet to be elucidated. However if this trend is repeated in natural ecosystems, this may have important implications for C and N cycling.     

Rhizodeposition under ambient and elevated CO2 levels

As global CO₂ levels rise, can soils store more carbon and so buffer atmospheric CO₂ levels? Answering this question requires a knowledge of the rates of C inputs to soil and of CO₂ outputs via decomposition. Below-ground inputs from roots are a major component of the C flow into soils but are still poorly understood. In this article, new techniques for measuring rhizodeposition are reviewed and discussed and the need for cross-comparisons between methods is identified. One component of rhizodeposition, root exudation, is examined in more detail and evidence is presented which suggests that current estimates of exudate flow into soils are incorrect. A mechanistic mathematical model is used to explore how exudate flows might change under elevated CO₂.     

Growth,CO2 exchange rate and dry matter partitioning in mungbean (Vigna radiata L.) grown under elevated CO2

This study was conducted to determine the effects of anticipated future level of CO2 on growth and dry matter partitioning of mungbean (Vigna radiata). Plants were grown from seedlings to maturity inside the open top chamber under amhient CO2 (350 +/- 25 microL L(-1)) and elevated CO2 (600 +/- 50 microL L(-1)) at Indian Agricultural Research Institute, New Delhi (India). Plants were harvested at 20, 35 and 50 days after germination. Mungbean plants grown under elevated CO2 concentration resulted in greater photosynthetic rate on a leaflet area basis and no acclimation in photosynthesis was recorded due to high CO2. Plants grown under CO, enrichmcnt were taller and attained greater leaf area along with more dry matter than ambient CO2 grown plants at all growth stages. Response to high CO, depends upon the growth stage of the plant and it was more at early growth stages compared to maturity stages. The high CO2 grown mungbean plants also exhibited increased root growth along with stem and leaves. There was a substantial increase in pod number and seed number/plant under elevated CO2 conditions. The increase in dry matter and growth of root, stem and leaves proved that CO2 enrichment of the atmosphere can stimulate photosynthetic rate which can ultimately lead to an increase in dry matter and growth.     

Plant regeneration through the direct induction of shoot buds from petiole explants of Jatropha curcas: a biofuel plant

An efficient and reproducible method for the regeneration of Jatropha curcas plants has been developed. The method employed direct induction of shoot buds from petiole explants, without the formation of an intervening callus using a Murashige and Skoog (MS) medium supplemented with different concentrations of thidiazuron (TDZ). The best induction of shoot buds (58.35%) and the number of shoot buds per explant (10.10) were observed when in vitro petiole explants were placed horizontally on MS medium supplemented with 2.27 µM TDZ after 6 weeks. The induced shoot buds were transferred to MS medium containing 10 µM kinetin (Kn), 4.5 µM 6-benzyl aminopurine (BAP) and 5.5 µM α-naphthaleneacetic acid (NAA) for shoot proliferation. The proliferated shoots could be elongated on MS medium supplemented with different concentrations and combinations of BAP, indole-3-acetic acid (IAA), NAA and indole-3-butyric acid (IBA). MS medium supplemented with 2.25 µM BAP and 8.5 µM IAA was found to be the best combination for shoot elongation and 3.01–3.91 cm elongation was achieved after 6 weeks. However, significant differences in plant regeneration and shoot elongation were observed among the genotypes studied. The orientation (horizontal or vertical) and source (in vitro or in vivo) of explants also significantly influenced plant regeneration. The elongated shoots could be rooted on half-strength MS medium supplemented with 2% sucrose, different concentrations and combinations of IBA, IAA and NAA, and 0.25 mg L⁻¹ activated charcoal. Half-strength MS medium supplemented with 2% sucrose, 15 µM IBA, 5.7 µM IAA, 5.5 µM NAA and 0.25 mg L⁻¹ activated charcoal was found to be the best for promoting rooting. The rooted plants could be established in soil with more than 90% survival.     

Leaf and canopy responses to elevated CO2 in a pine forest under free-air CO2 enrichment

Physiological responses to elevated CO₂ at the leaf and canopy-level were studied in an intact pine (Pinus taeda) forest ecosystem exposed to elevated CO₂ using a free-air CO₂ enrichment (FACE) technique. Normalized canopy water-use of trees exposed to elevated CO₂ over an 8-day exposure period was similar to that of trees exposed to current ambient CO₂ under sunny conditions. During a portion of the exposure period when sky conditions were cloudy, CO₂-exposed trees showed minor (7%) but significant reductions in relative sap flux density compared to trees under ambient CO₂ conditions. Short-term (minutes) direct stomatal responses to elevated CO₂ were also relatively weak (5% reduction in stomatal aperture in response to high CO₂ concentrations). We observed no evidence of adjustment in stomatal conductance in foliage grown under elevated CO₂ for nearly 80 days compared to foliage grown under current ambient CO₂, so intrinsic leaf water-use efficiency at elevated CO₂ was enhanced primarily by direct responses of photosynthesis to CO₂. We did not detect statistical differences in parameters from photosynthetic responses to intercellular CO₂ (A _net-C _i curves) for Pinus taeda foliage grown under elevated CO₂ (550 mol mol^–1) for 50–80 days compared to those for foliage grown under current ambient CO₂ from similar-sized reference trees nearby. In both cases, leaf net photosynthetic rate at 550 mol mol^–1 CO₂ was enhanced by approximately 65% compared to the rate at ambient CO₂ (350 mol mol^–1). A similar level of enhancement under elevated CO₂ was observed for daily photosynthesis under field conditions on a sunny day. While enhancement of photosynthesis by elevated CO₂ during the study period appears to be primarily attributable to direct photosynthetic responses to CO₂ in the pine forest, longer-term CO₂ responses and feedbacks remain to be evaluated.     

Cladode development, environmental responses of CO2 uptake, and productivity for Opuntia ficus-indica under elevated CO2

Opuntia ficus-indica, an extremely productive CAM plant cultivatedin many countries, was exposed to 36, 52, and 72–73 PaCO₂ in field plots and open-top chambers. Initiation of newcladodes (stem segments) was monitored until the canopy closed,after which bimonthly harvests maintained the plants for oneyear at a cladode area per unit ground area that is optimalfor biomass production. Doubling the CO₂ partial pressure slightlyincreased the number of first-order daughter cladodes growingon the basal (planted) cladodes after 3 months and nearly doubledthe number and area of second-order cladodes. When the C02 levelwas doubled, cladodes were 5% thicker after a few months and11 to 16% thicker after one year. Although the productivityenhancement by elevated C02 tended to decrease during the year,the annual above-ground dry-mass gain was 37 to 40% higher whenthe C02 level was doubled, reaching 65 tons hectare^–1year^–1 in a field plot. Well-watered cladodes at day/nightair temperatures of 25°C/15°C and a total daily photosyntheticphoton flux (PPF) of 15 mol m^–2 d^–1 in controlledenvironment chambers had 74% more net CO₂ uptake over 24 h at73 Pa than at 37 Pa CO₂. With doubled CO₂, the percentage enhancementof net CO₂ uptake increased as the PPF was lowered, as the temperaturewas raised, and during drought. Using an environmental productivityindex based on such factors, net CO₂ uptake and hence productivityof O. ficus-indica can be predicted for elevated CO₂ levelsand other variations accompanying global climate change. Key words: Crassulacean acid metabolism, environmental productivity index, gas exchange, global climate change, plant growth     

CO2浓度升高对干旱胁迫下小麦光合作用和抗氧化酶活性的影响

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Antiquity, botany, origin and domestication of Jatropha curcas (Euphorbiaceae), a plant species with potential for biodiesel production

Jatropha curcas is a multi-purpose plant species, with many advantages for biodiesel production. Its potential oil productivity is 1.9 t/ha, beginning the fourth year after planting. Nevertheless, limitations such as high harvest cost, lack of scientific konowledge and low profitability have prevented it from being utilized commercially. In order to provide information that could be useful to improve the status of this species as a bioenergy plant, we elucidated the center of origin and the center of domestication of J. curcas (Mexico). Evidence of the antiquity of knowledge of J. curcas by Olmeca people, who lived 3500-5000 years ago, reinforces its Mexican origin. The existence of non-toxic types, which only exist in that country, along with DNA studies, also strongly suggest that Mexico is the domestication center of this species. In Brazil, the Northern region of Minas Gerais State presents types with the highest oil content. Here we propose this region as a secondary center of diversity of J. curcas.     

Tidal marsh plant responses to elevated CO2, nitrogen fertilization,and sea level rise

Elevated CO₂ and nitrogen (N) addition directly affect plant productivity and the mechanisms that allow tidal marshes to maintain a constant elevation relative to sea level, but it remains unknown how these global change drivers modify marsh plant response to sea level rise. Here we manipulated factorial combinations of CO₂ concentration (two levels), N availability (two levels) and relative sea level (six levels) using in situ mesocosms containing a tidal marsh community composed of a sedge, Schoenoplectus americanus, and a grass, Spartina patens. Our objective is to determine, if elevated CO₂ and N alter the growth and persistence of these plants in coastal ecosystems facing rising sea levels. After two growing seasons, we found that N addition enhanced plant growth particularly at sea levels where plants were most stressed by flooding (114% stimulation in the + 10 cm treatment), and N effects were generally larger in combination with elevated CO₂ (288% stimulation). N fertilization shifted the optimal productivity of S. patens to a higher sea level, but did not confer S. patens an enhanced ability to tolerate sea level rise. S. americanus responded strongly to N only in the higher sea level treatments that excluded S. patens. Interestingly, addition of N, which has been suggested to accelerate marsh loss, may afford some marsh plants, such as the widespread sedge, S. americanus, the enhanced ability to tolerate inundation. However, if chronic N pollution reduces the availability of propagules of S. americanus or other flood‐tolerant species on the landscape scale, this shift in species dominance could render tidal marshes more susceptible to marsh collapse.     

桃蚜取食行为对大气CO_2浓度升高的响应

【目的】近年来随着人类活动的增加,温室气体尤其是大气CO_2浓度升高造成的虫害爆发已成为国际上关注的焦点,因此,研究拟南芥Arabidopsis thaliana上桃蚜取食行为的变化对大气CO_2浓度升高的响应意义重大。【方法】本研究以拟南芥和绿色桃蚜Myzus persicae为研究对象,利用野生型拟南芥Col-0,茉莉酸途径信号传导缺失突变体(jar1)、水杨酸途径信号传导缺失突变体(npr1)、乙烯途径信号传导缺失突变体(ein2-5)为材料,以大气CO_2浓度升高为影响因子,利用刺吸式电位仪(EPG)记录了桃蚜在不同处理的拟南芥上的取食波形。【结果】研究结果发现:CO_2浓度升高缩短了Col-0和jar1植株上蚜虫首次刺探时间和首次到达韧皮部的时间,却延长了npr1和ein2-5上蚜虫首次到达韧皮部的时间,降低了jar1植株上蚜虫总的刺探时间且增加了其总的取食韧皮部时间,但没有改变其它基因型植株上蚜虫总的刺探和取食时间;同时增加了野生型植株上蚜虫的刺探频率,却没有影响其它基因型植株上的刺探频率。【结论】CO_2浓度升高降低了野生型植株和jar1植株抗性,有利于蚜虫到达韧皮部;却增加了npr1和ein2-5上的植物抗性,从而不利于蚜虫到达韧皮部。     

Up-regulation of sucrose phosphate synthase in rice grown under elevated CO2 and temperature

Rice (Oryza sativa L. cv. IR-30) was grown season-long in outdoor, controlled-environment chambers at 33 Pa CO₂ with day/night/paddy-water temperatures of 28/21/25 °C, and at 66 Pa CO₂ with five different day/night/paddy-water temperature regimes (25/18/21, 28/21/25, 31/24/28, 34/27/31 and 37/30/34 °C). Sucrose phosphate synthase (SPS) activities in leaf extracts at 21, 48 and 81 days after planting (DAP) were assayed under saturating and selective (limiting) conditions. Diel SPS activity data indicated that rice SPS was light regulated; with up to 2.2-fold higher rates during the day. Throughout the growth season, leaf SPS activities were up-regulated in the CO₂-enriched plants, averaging 20 and 12% higher than in ambient-CO₂ grown plants in selective and saturating assays, respectively. Similarly, SPS activities increased 2.4% for each 1 °C rise in growth temperature from 25 to 34 °C, but de creased 11.5% at 37 °C. Leaf sucrose content was higher, and mirrored SPS activity better, than starch, although starch was more responsive to CO₂ treatment. Leaf sucrose and starch contents were significantly higher throughout the season in plants at elevated CO₂, but the N content averaged 6.5% lower. Increasing growth temperatures from 25 to 37 °C caused a linear decrease (62%) in leaf starch content, but not in sucrose. Consequently, the starch:sucrose ratio declined with growth temperature. The data are consistent with the hypothesis that the up-regulation of leaf SPS may be an acclimation response of rice to optimize the utilization and export of organic-C with the increased rates of inorganic-C fixation in elevated CO₂ or temperature growth regimes.