Responses of Artemisia annua L. to lead and salt-induced oxidative stress

The Artemisia annua L. plants were subjected separately to NaCl (0–160 mM) and lead acetate (0–500 μM) at the age of 90 days (S1 treatment) and 120 days (S2 treatment). The treated plants were studied on 100, 130 and 160 days after sowing (DAS) in S1, and on 130 and 160 DAS in S2 treatments for lipid peroxidation rate, photosynthetic rate (Pn), chlorophyll content, artemisinin concentration and artemisinin yield in leaf samples and for total biomass accumulation. The treatments enhanced lipid peroxidation at all stages of plant growth and increased the concentration and yield of artemisinin at 100 and 130 DAS in S1 and S2, respectively, while other parameters declined at all growth stages. The magnitude of changes was greater in lead-treated than in salt-treated plants. Both treatments induced oxidative stress which might have damaged the photosynthetic apparatus resulting in a loss of chlorophyll content and a decline in photosynthetic rate, biomass accumulation and artemisinin production. The increase in artemisinin content, observed during the early phase of plant growth, might be due to a sudden conversion of its precursors (e.g. artemisinic acid/dihydroartemisinic acid) to artemisinin by activated oxygen species under oxidative stress.     

Response of photosynthesis and chlorophyll fluorescence to acute ozone stress in tomato (Solanum lycopersicum Mill.)

The crop sensitivity to ozone (O₃) is affected by the timing of the O₃ exposure, by the O₃ concentration, and by the crop age. To determine the physiological response to the acute ozone stress, tomato plants were exposed to O₃ at two growth stages. In Experiment I (Exp. I), O₃ (500 μg m^?3) was applied to 30-d-old plants (PL30). In Experiment II (Exp. II), three O₃ concentrations (200, 350, and 500 μg m^?3) were applied to 51-d-old plants (PL51). The time of the treatment was 4 h (7:30–11:30 h). Photosynthesis and chlorophyll fluorescence measurements were done 4 times (before the exposure; 20 min, 20 h, and 2–3 weeks after the end of the treatment) using a LI-COR 6400 photosynthesis meter. The stomatal pore area and stomatal conductance were reduced as the O₃ concentration increased. Ozone induced the decrease in the photosynthetic parameters of tomato regardless of the plant age. Both the photosystem (PS) II operating efficiency and the maximum quantum efficiency of PSII photochemistry declined under the ozone stress suggesting that the PSII activity was inhibited by O₃. The impaired PSII contributed to the reduced photosynthetic rate. The greater decline of photosynthetic parameters was found in the PL30 compared with the PL51. It proved the age-dependent ozone sensitivity of tomato, where the younger plants were more vulnerable. Ozone caused the degradation of photosynthetic apparatus, which affected the photosynthesis of tomato plants depending on the growth stage and the O₃ concentration.     

Effects of NaCl stress on the growth and photosynthetic characteristics of Ulmus pumila L. seedlings in sand culture

The effects of NaCl stress on the growth and photosynthetic characters of Ulmus pumila L. seedlings were investigated under sand culture condition. With increasing NaCl concentration, main stem height, branch number, leaf number, and leaf area declined, while Na⁺ content and the Na⁺/K⁺ ratio in both expanded and expanding leaves increased. Na⁺ content was significantly higher in expanded leaves than in those just expanding. Chlorophyll (Chl) a and Chl b contents declined as NaCl concentration increased. The net photosynthetic rate, intercellular CO₂ concentration, stomatal conductance, and transpiration rate also declined, but stomatal limitation value increased as NaCl concentration increased. Both the maximal quantum yield of PSII photochemistry and the effective quantum yield of PSII photochemistry declined as NaCl concentration rose. These results suggest that the accumulation of Na⁺ in already expanded leaves might reduce damage to the expanding leaves and help U. pumila endure high salinity. The reduced photosynthesis in response to salt stress was mainly caused by stomatal limitation.     

冬小麦光合特征及叶绿素含量对保水剂和氮肥的响应

以不施保水剂和氮（N）肥为对照,测定了保水剂（60 kg·hm^-2）与不同N肥水平（0、225、450 kg·hm^-2）及其配施条件下大田小麦的光合特征、叶绿素含量和水分利用效率等指标,研究了冬小麦拔节期和灌浆期光合生理特征、叶绿素含量及水分利用对保水剂和N肥的响应.结果表明：灌浆期各处理的光合速率、气孔导度、胞间CO₂浓度、叶片水分利用效率及叶绿素含量均大于拔节期.在拔节期,单施N肥条件下,随施N量的增加,单叶水分利用效率提高,光合速率、气孔导度、胞间CO₂浓度及蒸腾速率均先增后减;225 kg·hm^-2 N肥处理的叶绿素含量最高.施用保水剂后,随施N量的增加,胞间CO₂浓度降低,而光合速率等均提高;单施保水剂及其与N肥配施提高了叶绿素含量,而过多N肥效果不显著在灌浆期,单施N肥显著提高了小麦的光合速率及水分利用效率,降低了气孔导度、胞间CO₂浓度及蒸腾速率;叶绿素含量随N肥用量的增加而增加.施用保水剂后,随N肥用量的增加,光合速率和叶片水分利用效率均先增后减,而胞间CO₂浓度和蒸腾速率先减后增,但均低于对照,气孔导度随施N量的增加而提高.单施保水剂的叶绿素含量显著提高,但其与N肥配施叶绿素含量有所降低.保水剂与N肥配合施用显著提高了小麦的千粒重、产量及水分生产效率.其中,保水剂与225 kg·hm^-2N肥配施处理的产量及水分生产效率均最高.     

Effects of cadmium on growth, photosynthetic rate and chlorophyll content in leaves of soybean seedlings

Cadmium is a widely spread pollutant and the objective of this study was to study the effects of different concentrations of Cd (0, 50, and 100 μM) on the soybean seedlings treated for 10 d. The growth was inhibited and chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, probability that a trapped exciton moves an electron into the electron transport chain beyond QA — (ET_O/TR_O), performance indexes (PI_ABS), and amount of active reaction centres per excited cross section (RC/CS_O) were decreased with the increasing Cd concentration. The leaf reflectance increased in visual range (500–670 nm) and decreased in near-infrared range (750–1 000 nm). The accumulation of Cd in the roots was much higher than that in the stems and leaves.     

Effects of Arsenic on Growth, Photosynthetic Activity, and Accumulation in Two New Hyperaccumulating Populations of Isatis cappadocica Desv.

The effect of arsenic on leaf photosynthetic rate, growth responses, and accumulation capability of Isatis cappadocica Desv., a Brassica collected from Iranian arsenic-contaminated mine spoils and control populations, was investigated. Both populations of I. cappadocica were considerably more tolerant than the reference Brassica species (Descurainia sophia). The 1,000 μM arsenate exposure inhibited root growth completely in D. sophia, but only by 50 and 40 % in the nonmine and mine populations of I. cappadocica, respectively. Furthermore, the chlorophyll contents of both populations of I. cappadocica were not statistically different, especially when plants were exposed to 5–800 μM As. The chlorophyll a fluorescence kinetics (F _v/F _m) and electron transfer rate values of treated I. cappadocica populations remained unaffected, indicating normal photosynthetic efficiency and strength of plants in the presence of arsenic. After 28 days of exposure to 1,300 μM As, shoot arsenic concentrations of mine and nonmine populations reached 310 and 345 mg kg^?1, respectively, with the arsenic transfer factor and bioaccumulation greater than 1.0. According to these results, it was shown that I. cappadocica had strong tolerance to and the capability to hyperaccumulate arsenic; therefore, it is a potential As hyperaccumulator.     

The effects of gibberellic acid on photosynthetic pigments and oxygen evolution inChlamydomonas andAnacystis

Gibberellic acid (GA₃) generally increased the contents of chlorophyll but not carotenoid in bothChlamydomonas reinhardii andAnacystis nidulans grown under continuous irradiation. The photosynthetic oxygen evolution of the algae was also affected by GA₃ except for the high (100 μM) concentration of GA₃.     

The role of ammonium in photoprotection against high irradiance in the red alga Grateloupia lanceola

Combined and/or interactive effects of inorganic nitrogen (as ammonium) and irradiance on the accumulation of nitrogenous compounds, like UV-absorbing mycosporine-like amino acids (MAAs), chlorophyll a and phycobiliproteins, were examined in the red alga Grateloupia lanceola (J. Agardh) J. Agardh in a high irradiance laboratory exposure and a subsequent recovery period under low light. Also, photosynthetic activity as in vivo chlorophyll fluorescence of photosystem II, i.e. optimum quantum yield (F_v/F_m), electron transport rate (ETR) and quantum efficiency, were examined. Photosynthetic activity, phycobiliproteins and internal nitrogen content declined during the 3-day PAR (photosynthetically active radiation; 600 μmol s⁻¹ m⁻²) and PAR + UVR (ultraviolet radiation; UVB 280–315 nm 0.8 W m⁻², UVA 315–400 nm 16 W m⁻²) exposure. Ammonium supplied in the culture medium (0, 100 and 300 μM NH₄Cl) modified the responses of the alga to high irradiance exposures in a concentration dependent manner, mainly with respect to recovery, as the highest recovery during a 10-day low light period was produced under elevated concentration of ammonium (300 μM). The recovery of photosynthetic activity and phycobiliproteins was enhanced in the algae previously incubated under PAR + UVR as compared to exposure to only PAR, suggesting a beneficial effect of UVR on recovery or photoprotective processes under enriched nitrogen conditions. However, the content of MAAs did not follow the same pattern and thus it could not be concluded as the cause of observed enhanced recovery.     

Multi-Wall Carbon Nanotubes Effects on Plant Seedlings Growth and Cadmium/Lead Uptake In Vitro

The effects of multi-wall carbon nanotubes (MWCNTs) on plant growth and Cd/Pb accumulation was investigated on seedlings of three plant species including Brassica napus L., Helianthus annus L. and Cannabis sativa L. The experiment consisted of MWCNTs on three concentration levels (0, 10, 50 mg/L) and 200 μM CdCl₂ or 500 μM Pb(NO₃)₂. MWCNTs application effectively improved root and shoot growth inhibited by Cd and Pb salts. In B. napus, total chlorophyll (Chl) content increased by both MWCNTs 10 and 50 mg/L exposure under cadmium or lead stress. MWCNT 10 mg/L mitigated the deleterious effects of Cd ions on total chlorophyll content of H. annus and C. sativa. Wherease higher concentration of MWCNTs decreased Chl content under either Cd or Pb treatments on sunflower seedlings. MWCNT10 effectivly raised cadmium accumulation in seedlings of all three species. MWCNT10 and 50 mg/L also caused higher Pb accumulation in canola and cannabis seedlings, respectively. Based on the results, it seems that the effects of MWCNTs on growth parameters and heavy metal accumulation in plant seedlings is strongly depends on heavy metal type, MWCNTs concentration and plant species.     

Effect of imazapic residues on photosynthetic traits and chlorophyll fluorescence of maize seedlings

The influence of various concentrations of imazapic residues (0–800 μg kg^–1) on the growth, chlorophyll content, and photosynthetic characteristics of maize seedlings was studied in a greenhouse pot experiment. Plant height, root length, shoot dry mass, root dry mass, and total dry mass of maize declined with the increase of imazapic residue concentrations. The root/shoot ratio initially decreased and then increased in presence of imazapic, which indicated that the effects of imazapic residues on plant height and root length might differ in maize seedlings. Lowered chlorophyll content and net photosynthetic rate were observed in leaves of maize seedlings in all treatments and indicated a dose-response relationship to imazapic concentrations. Intercellular carbon dioxide concentration, transpiration rate, and stomatal conductance also declined to varying extents, but the chlorophyll a/b ratio increased gradually together with the increase of imazapic residue concentrations. Generally, the maize seedlings were negatively affected by the imazapic residues in soil. Response of root length and biomass to imazapic residues could be the important index for maize variety selection.     

Responses of <Emphasis Type="Italic">Nigella sativa</Emphasis> to foliar application of gibberellic acid and kinetin

Foliar sprays of water or 1, 10 and 100 μM aqueous solutions of gibberellic acid (GA₃) or kinetin (KIN) were applied to 40-d-old plants of Nigella sativa (L.) to study their effects on net photosynthetic rate, nitrogen metabolism, and the seed yield. 10 μM solutions of both the hormones, especially GA₃, appreciably increased the activities of nitrate reductase and carbonic anhydrase, chlorophyll and total protein contents and net photosynthetic rate in the leaves, along with capsule number and seed yield plant⁻¹, at harvest.     

Effects of cytokinin on photosynthetic gas exchange, chlorophyll fluorescence parameters and antioxidative system in seedlings of eggplant (Solanum melongena L.) under salinity stress

The effects of 6-benzyladenine (6-BA) on plant growth, photosynthetic gas exchange, chlorophyll fluorescence and antioxidant systems of eggplant (Solanum melongena L.) under salt stress were investigated. Eggplant seedlings were exposed to 90?mM NaCl with four levels of 6-BA (5, 10, 20 and 50???M) for 10?days. 6-BA at lower concentrations increased chlorophyll concentration, the net photosynthetic rate (P _N), stomatal conductance (g _s), and transpiration rate (E), intercellular CO₂ concentration (C _i) and water use efficiency (WUE), as well as the quantum efficiency of PSII photochemistry (??PSII), photochemical quenching (q _p), and decreased non-photochemical quenching (NPQ), while higher concentrations reduced the effects or even exacerbated the occurrence of photosynthetic capacity. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) increased significantly during salt treatments, and induced the increase of the activities of these enzymes at certain concentrations of 6-BA. 6-BA also reduced significantly malonaldehyde (MDA) contents and O ₂ ^·? production. It was concluded that 6-BA could alleviate the detrimental effects of salt stress on plant growth by increasing photosynthetic efficiency and enhancing antioxidant enzyme systems in leaves at a proper concentration and of the varying 6-BA concentrations used, the most effective concentration for promoting growth was 10???M under saline conditions.     

Cadmium induced oxidative stress and biochemical responses in cyanobacterium <Emphasis Type="Italic">Nostoc muscorum</Emphasis>

The present study deals with the growth, photosynthesis, oxidative stress and heavy metal accumulation ability of Nostoc muscorum exposed to different levels (2, 4, 8, 16, 20 μM) of cadmium (Cd) concentrations. Growth and photosynthetic pigments i.e., chlorophyll a, carotenoids and phycocyanin were significantly affected by cadmium exposure and inhibition was found to be dose dependent. ¹⁴C-fixation appeared to be more sensitive to Cd than whole cell oxygen evolution. Significant accumulation of Cd in the cells of N. muscorum was noticed after 1 and 2 h of exposure and the accumulation rate was dose and time dependent. Furthermore, the levels of superoxide radicals and hydrogen peroxide (H₂O₂) were found significantly increased by cadmium exposure which in turn accelerated the formation of malondialdehyde (MDA) content, and protein and DNA damage. The selected dose of Cd (20 μM) showed the induction of new polypeptide of ~23.24 kD and the loss of ~37.84 kD and ~69.63 kD whereas the remaining bands were inhibited as compared to control. Significant DNA fragmentation which is a hallmark of programmed cell death (PCD) was also observed in the cells treated with 20 μM of Cd for 48 h. The decrease in proline and total phenol content at 8 and 16 μM suggest that the cells of N. muscorum were not able to mitigate the oxidative stress induced by cadmium exposure. Similarly, the decreased activities of antioxidant enzymes i.e., superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) also indicates the failure of the antioxidant defense system of N. muscorum to survive at higher concentration (8 and 16 μM) of cadmium.     

Antioxidant capacity and cadmium accumulation in parsley seedlings exposed to cadmium stress

Parsley (Petroselinum hortense L.) plants cultivated under controlled conditions were exposed to different doses of cadmium to investigate the antioxidant capacity and cadmium accumulation in the samples. Two-months-old parsley seedlings were treated with four different concentrations of CdCl₂ (0, 75, 150, and 300 μM) for fifteen days. Cadmium level in leaves increased significantly by increasing the Cd contamination in the soil. Total chlorophyll and carotenoid content declined considerably with Cd concentration. Cd treatment caused a significant increase lipid peroxidation in tissue of leaf. Superoxide dismutase activity (SOD, EC 1.15.1.1) increased partially at 75 and 150 μM CdCl₂ concentrations whereas the activity decreased at 300 μM CdCl₂. Catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) activities were reduced by Cd application. Total phenolic compound amount increased significantly with increasing Cd concentration, as ferric reduction power, superoxide anion radical, and DPPH˙ free radical scavenging activities elevated slightly by the concentration. These results suggest that antioxidant enzymes activities were repressed depending on accumulation of cadmium in leaves of parsley while the non-enzymatic antioxidant activities slightly increased.     

Effects of light quality on the chloroplastic ultrastructure and photosynthetic characteristics of cucumber seedlings

To understand how light quality influences plant photosynthesis, we investigated chloroplastic ultrastructure, chlorophyll fluorescence and photosynthetic parameters, Rubisco and chlorophyll content and photosynthesis-related genes expression in cucumber seedlings exposed to different light qualities: white, red, blue, yellow and green lights with the same photosynthetic photon flux density of 100 μmol m^?2 s^?1. The results revealed that plant growth, CO₂ assimilation rate and chlorophyll content were significantly reduced in the seedlings grown under red, blue, yellow and green lights as compared with those grown under white light, but each monochromatic light played its special role in regulating plant morphogenesis and photosynthesis. Seedling leaves were thickened and slightly curled; Rubisco biosynthesis, expression of the rca, rbcS and rbcL, the maximal photochemical efficiency of PSII (Fv/Fm) and quantum yield of PSII electron transport (Ф_PSII) were all increased in seedlings grown under blue light as compared with those grown under white light. Furthermore, the photosynthetic rate of seedlings grown under blue light was significantly increased, and leaf number and chlorophyll content of seedlings grown under red light were increased as compared with those exposed to other monochromatic lights. On the contrary, the seedlings grown under yellow and green lights were dwarf with the new leaves etiolated. Moreover, photosynthesis, Rubisco biosynthesis and relative gene expression were greatly decreased in seedlings grown under yellow and green light, but chloroplast structural features were less influenced. Interestingly, the Fv/Fm, Ф_PSII value and chlorophyll content of the seedlings grown under green light were much higher than those grown under yellow light.     

Effects of chilling and high temperatures on photosynthesis and chlorophyll fluorescence in leaves of watermelon seedlings

The effects of chilling (CT, day/night temperatures of 12/10 °C, an irradiance of 250 μmol m^?2 s^?1), chilling combined with a low irradiance (CL, 12/10 °C, 80 μmol m^?2 s^?1), and a high temperature (HT, 42/40 °C, 250 μmol m^?2 s^?1) on chlorophyll content, chlorophyll fluorescence, and gas exchange were studied in two watermelon cultivars, ZJ8424 and YS01, differing in their resistance. The chlorophyll content, net photosynthetic rate (P_N), stomatal conductance (g_s), and transpiration rate (E) decreased substantially, whereas the intercellular CO₂ concentration (c_i) increased when the two watermelon cultivars were grown under these stresses. The photosynthetic parameters showed greater changes at chilling than at the high temperature, and the CL caused a more pronounced inhibition in PN compared with the CT. After 2 d exposure to the CT, YS01 had higher P_N, g_s, and E, but a lower ci compared with ZJ8424. The maximum efficiency of photosystem (PS) II photochemistry (F_v/F_m), effective quantum yield of PS II photochemistry (Φ_PSII), photochemical quenching (qP), and electron transport rate (ETR) decreased under the CT and CL but showed only a slight drop under the HT. All these stresses significantly increased non-photochemical quenching (NPQ). The CT brought more damage to the photosynthetic apparatus of leaves compared with the CL. In addition, after returning to normal conditions (25/15 °C, 250 μmol m^?2 s^?1) for 3 d, the photosynthetic parameters recovered to pre-stress levels in HT treated seedlings but not in CT treated seedlings. In conclusion, the low irradiance could help to alleviate the extent of photoinhibition of PS II photochemistry caused by chilling and cv. ZJ8424 was more sensitive to the extreme temperatures than cv. YS01.     

Leaf chloroplast ultrastructure and photosynthetic properties of a chlorophyll-deficient mutant of rice

Leaf chloroplast ultrastructure and photosynthetic properties of a natural, yellow-green leaf mutant (ygl1) of rice were characterized. Our results showed that chloroplast development was significantly delayed in the mutant leaves compared with the wild-type rice (WT). As leaves matured, more grana stacks formed concurrently with increasing leaf chlorophyll (Chl) content. Except for the lower intercellular CO₂ concentration, the ygl1 plants had a higher leaf net photosynthetic rate, stomatal conductance, and transpiration rate than those of the WT plants. Under equal amounts of Chl, the excitation energy of PSI and PSII was much stronger in the mutant than that in the WT. The ygl1 plants showed higher nonphotochemical quenching and lower photochemical quenching. They also exhibited higher actual photochemical efficiency of PSII with a higher electron transport rate. Under the light of 200 μmol(photon) m^?2 s^?1, the ygl1 mutant showed lesser deepoxidation of violaxanthin in the xanthophyll cycle than WT, but it increased substantially under strong light conditions. In conclusion, the photosynthetic machinery of the ygl1 remained stable during leaf development. The plants were less sensitive to photoinhibition compared with WT due to the active xanthophyll cycle. The ygl1 plants were efficient in both light harvesting and conversion of solar energy.     

盐胁迫对沙拐枣光合生理特性的影响

以采自甘肃民勤一年生的沙拐枣幼苗为试材,对不同NaCl浓度(0、50、100、200、300mmol·L~(-1))处理下沙拐枣光合生理特性进行分析,并对各生理指标与地上生物量进行灰色关联度分析,以探讨荒漠植物沙拐枣的抗盐机理,为沙拐枣的保护及其恢复荒漠生态系统稳定提供理论依据。结果显示:随着NaCl浓度的升高,沙拐枣同化枝内脯氨酸含量逐渐增大,而其可溶性糖含量逐渐减小;在低浓度NaCl(50mmol·L~(-1) NaCl)处理下,同化枝光合参数均增加,且净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)均达到最大值,比对照分别显著增加了33.3%、68.0%、60.8%;与50mmol·L~(-1) NaCl相比,处理浓度超过50mmol·L~(-1) NaCl时,Pn、Gs、Tr均降低;同化枝叶绿素b含量随着NaCl浓度的增加而降低,而叶绿素a和总叶绿素含量均呈先增加后降低的趋势。灰色关联度分析发现,同化枝的Tr、Gs、Ci以及叶绿素b与地上生物量的关联度较大。研究表明,低盐浓度NaCl激活了沙拐枣的某些生理机制,有利于植株的光合作用和生长,而植物在高盐浓度胁迫时能通过调节脯氨酸和可溶性糖的含量,减少叶绿素含量、Pn和Tr等维持自身的生长。     

Photosynthetic response of poikilochlorophyllous desiccation-tolerant Pleurostima purpurea (Velloziaceae) to dehydration and rehydration

The poikilochorophyllous, desiccation-tolerant (PDT) angiosperm, Pleurostima purpurea, normally occurs in less exposed rock faces and slightly shady sites. Our aim was to evaluate the light susceptibility of the photosynthetic apparatus during dehydration-rehydration cycle in P. purpurea. In a controlled environment, the potted plants were subjected to water deficit under two different photosynthetic photon flux densities [PPFD, 100 and 400 μmol(photon) m^?2 s^?1]. In the higher PPFD, net photosynthetic rate (P _N) become undetectable after stomata closure but photochemical efficiency of photosystem II, electron transport rate, and photochemical quenching coefficient were maintained relatively high, despite a partial decrease. The photochemical activity was inhibited only after the complete loss of chlorophylls, when leaf relative water content dropped below 72% and total carotenoids reached maximal accumulation. Nonphotochemical energy dissipation increased earlier in response to dehydration under higher PPFD. P _N and photochemical activity were fully recovered after rehydration under both light treatments. Our results suggested that the natural occurrence of P. purpurea should not be restricted by the light intensity during the complete desiccation-rehydration cycles.     

Physiological and ultra-structural changes in Brassica napus seedlings induced by cadmium stress

The effects of cadmium on physiological and ultrastructural characteristics were evaluated in 6-d-old seedlings of two Brassica napus L. cultivars Zheda 619 and ZS 758. Results show that Cd at lower concentration (100 μM) stimulated the seedling growth but at higher concentration (500 μM) inhibited the growth of both cultivars, decreased content of photosynthetic pigments, activities of antioxidant enzymes, and increased the content of malondialdehyde and reactive oxygen species. Cd content in different parts of seedlings was higher in ZS 758 than in Zheda 619. Electron micrographs illustrated that 500 μM Cd severely damaged the leaf and root tip cells of both cultivars. Under Cd stress, the size and number of starch grains, plastoglobuli, and lipid bodies in the chloroplasts increased. In the root tip cells, enlarged vacuoles, diffused cell walls, and undeveloped mitochondria were detected.