Photosynthetic Rate, Growth, and Yield of Mustard Plants Sprayed with 28-Homobrassinolide

Thirty-day-old plants of mustard (Brassica juncea L.) were sprayed with 10⁻¹⁰, 10⁻⁸, or 10⁻⁶ M aqueous solution of 28-homobrassinolide (HBR). The HBR-treated plants were healthier than those treated with water and yielded more. Maximum increase over control was found in 60-d-old, 10⁻⁸ M-HBR-treated plants in fresh and dry mass per plant, carbonic anhydrase (CA, E.C. 4.2.1.1) activity, and net photosynthetic rate (P _N), at harvest in number of pods per plant and seed yield per plant (the respective values were 25, 30, 34, 69, 24, and 29 %). A further increase in the concentration of HBR (10⁻⁶ M) did not make any additional impact on the growth and yield. Increased CA activity and P _N were correlated with growth and seed yield. This revised version was published online in August 2006 with corrections to the Cover Date.     

Carbonic Anhydrase,Photosynthesis, and Seed Yield in Mustard Plants Treated with Phytohormones

The leaves of 30-d-old plants of Brassica juncea Czern & Coss cv. Varuna were sprayed with 10^–6 M aqueous solutions of indole-3-yl-acetic acid (IAA), gibberellic acid (GA₃), kinetin (KIN), and abscisic acid (ABA) or 10^–8 M of 28-homobrassinolide (HBR). All the phytohormones, except ABA, improved the vegetative growth and seed yield at harvest, compared with those sprayed with deionised water (control). HBR was most prominent in its effect, generating 32, 30, 36, 70, 25, and 29 % higher values for dry mass, chlorophyll content, carbonic anhydrase (E.C. 4.2.1.1) activity, and net photosynthetic rate in 60-d-old plants, pods per plant, and seed yield at harvest, over the control, respectively. The order of response to various hormones was HBR > GA₃ > IAA > KIN > control > ABA.     

Effect of gibberellic acid on carbonic anhydrase,photosynthesis, growth and yield of mustard

The plants of mustard (Brassica juncea L.) were treated with 0, 25 and 50 ΜM gibberellic acid (GA₃) at three fully developed leaf stage (30 d after sowing). Effect of GA₃ on carbonic anhydrase activity, photosynthetic rate, leaf area index and dry mass was studied at 50, 70 and 90 d after sowing. At harvest 1000 seed mass, pod number and seed yield were recorded. GA₃ treatment (50 ΜM) enhanced all the characteristics studied.     

Arabidopsis thaliana carbonic anhydrase: cDNA sequence and effect of CO2 on mRNA levels

A full-length cDNA clone encoding carbonic anhydrase was isolated from an Arabidopsis thaliana (Columbia) leaf library. Comparison of the derived amino acid sequence obtained from this clone with those of pea and spinach reveals a considerable degree of identity. The carbonic anhydrase cDNA was used to probe the level of RNA encoding this protein in the leaves of plants grown in elevated CO₂ (660 ppm). We have found that under these conditions the steady-state level of carbonic anhydrase mRNA was increased in comparison with control plants grown in normal atmospheric concentrations of CO₂ (330 ppm). This raises the intruiging possibility that there exists in higher plants a mechanism for perceiving and responding to changes in environmental CO₂ concentrations at the genetic level.     

Similarity of growth patterns between plantlets and seedlings of Brassica campestris L. under different in vitro environmental conditions

Explants and seeds of Brassica campestris L. were cultured on Murashige & Skoog (1962) medium with and without sucrose in a vessel with different numbers of air changes per hour under different PPF (photosynthetic photon flux) conditions. The growth and development of plantlets in the vessel were similar to those of seedlings when cultured under the same in vitro environmental conditions. The growth and development of seedlings when cultured under the same in vitro environmental conditions. The growth and development of plantlets/seedlings were greater for treatments with a higher number of air changes per hour and a higher PPF regardless of the sucrose concentration in the culture medium.The CO₂ concentration in the vessel with a lower number of air changes per hour decreased to approximately 100 ppm during the photoperiod on day 21 due to the photosynthetic activities of the plantlets/seedlings. The low CO₂ concentration, in turn, reduced the net photosynthetic rate of plantlets/seedlings in the vessel, and thus affected their growth and development.Abbreviations C_in CO₂ concentration in the culture vessel - C_out CO₂ concentration in the culture room - MS mineral composition of Murashige & Skoog (1962) medium - PPF photosynthetic photon flux     

油菜类型和品种对外来入侵杂草小子虉草的替代控制作用

外来入侵植物小子虉草（Phalaris minor Retz.）是世界公认的冬季农田恶性杂草,掌握农作物对其替代控制作用具有重要的研究价值。前期研究表明,油菜是替代控制小子虉草的优良农作物,然而,目前尚不清楚油菜类型与品种对其控制能力的影响。为此选取与小子虉草同域发生的不同类型（白菜型油菜、芥菜型油菜和甘蓝型油菜）油菜品种各3种,通过田间小区实验和室内化感作用测定,对比研究其对小子虉草的生长、繁殖、表型以及化感作用的影响。田间实验显示：竞争方式（种内或种间竞争）和油菜类型对小子虉草的地上生物量、种子数、株高、分枝数、叶面积和比叶面积存在极显著（P=0.0001）影响;而油菜品种对小子虉草的地上生物量（P=0.6064）、种子数（P=0.3577）、株高（P=0.4279）、分枝数（P=0.6357）、叶面积（P=0.8839）和比叶面积（P=0.3424）均无显著影响。3种类型油菜对小子虉草生长、繁殖以及表型的影响存在明显差异,其中芥菜型油菜对小子虉草的上述指标的影响最强,而白菜型油菜的影响最弱。室内生物测定显示,油菜对小子虉草具有化感抑制作用,当供试油菜叶片水提液浓度为0.1 g/mL时,小子虉草种子的萌发和幼苗的株高、根长、生物量均被显著抑制;研究也表明不同类型油菜对小子虉草的化感作用显著不同,同等条件下,芥菜型油菜对小子虉草的化感抑制作用最强。综上所述,油菜类型对外来入侵小子虉草的控制作用存在显著差异,其中芥菜型油菜对植物小子虉草的替代控制作用明显优于白菜型油菜和甘蓝型油菜,而其强的化感抑草特性或许是其强控草能力的原因之一。另外,本研究也为进一步利用油菜替代控制入侵植物小子虉草提供了参考。     

Activity of 1-Aminocyclopropane Carboxylic Acid Synthase in Two Mustard (Brassica juncea L.) Cultivars Differing in Photosynthetic Capacity

The pattern of activity of 1-aminocyclopropane carboxylic acid synthase (ACS) was similar to photosynthetic and growth traits observed at 30, 45, and 60 d after sowing in mustard (Brassica juncea L.) cultivars Varuna and RH 30 differing in photosynthetic capacity. Higher activity of ACS and therefore ethylene release in Varuna than RH 30 increased stomatal conductance, intercellular CO₂ concentration, carboxylation rate (carbonic anhydrase and intrinsic water use efficiency), and thus net photosynthetic rate (P _N) and leaf and plant dry masses (DM) at all sampling times. Moreover, Varuna also had larger leaf area which contributed to higher P _N and DM. A positive correlation between ACS activity and P _N and leaf area was found in both the cultivars. Thus ACS activity may affect P _N through ethylene-induced changes on foliar gas exchange and leaf growth.     

Antioxidant defense system in leaves of Indian mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis>) and rape (<Emphasis Type="Italic">Brassica napus</Emphasis>) under cadmium stress

Plant species capable of hyper-accumulating heavy metals are of considerable interest for phytoremediation, and differ in their ability to accumulate metals from environment. Using two brassica species (Brassica juncea and Brassica napus), nutrient solution experiments were conducted to study variation in tolerance to cadmium (Cd) toxicity based on (1) lipid peroxidation and (2) changes in antioxidative defense system in leaves of both plants (i.e., superoxide dismutase (SOD EC 1.15.1.1), catalase (CAT EC 1.11.1.6), ascorbate peroxidase (APX EC 1.11.1.11), guaiacol peroxidase (GPX EC 1.11.1.7), glutathione reductase (GR EC 1.6.4.2), levels of phytochelatins (PCs), non-protein thiols (NP-SH), and glutathione. Plants were grown in nutrient solution under controlled environmental conditions, and subjected to increasing concentrations of Cd (0, 10, 25 and 50 μM) for 15 days. Results showed marked differences between both species. Brassica napus under Cd stress exhibited increased level of lipid peroxidation, as was evidenced by the increased malondialdehyde (MDA) content in leaves. However, in Brassica juncea treated plants, MDA content remained unchanged. In Brassica napus, with the exception of GPX, activity levels of some antioxidant enzymes involved in detoxification of reactive oxygen species (ROS), including SOD, CAT, GR, and APX, decreased drastically at high Cd concentrations. By contrast, in leaves of Brassica juncea treated plants, there was either only slight or no change in the activities of the antioxidative enzymes. Analysis of the profile of anionic isoenzymes of GPX revealed qualitative changes occurring during Cd exposure for both species. Moreover, levels of NP-SH and PCs, monitored as metal detoxifying responses, were much increased in leaves of Brassica juncea by increasing Cd supply, but did not change in Brassica napus. These results indicate that Brassica juncea plants possess the greater potential for Cd accumulation and tolerance than Brassica napus.     

Comparison of photosynthetic activity of <Emphasis Type="Italic">Orychophragmus violaceus</Emphasis> and oil-seed rape

Orychophragmus violaceus, Brassica campestris cv. Chuanyou No.8, and Brassica juncea cv. Luzhousileng diurnal changes of net photosynthetic rate (P _N) and activities of carbonic anhydrase (CA) of leaves were studied. One uni-modal curve occurred at the diurnal changes of P _N in O. violaceus, but bimodal curves were found in B. campestris and B. juncea. Thus photosynthetic midday depression was not found in O. violaceus but in both Brassica species. Midday depression of P _N in O. violaceus was not related to high temperature or low humidity at midday but to the activity of CA.     

Characteristics of oviposition behaviour of the pollen beetle, Meligethes aeneus on four different host plants

Oviposition behaviour of Meligethes aeneus F. (Coleoptera: Nitidulidae) is characterised and quantified on four different plant species. Six behavioural components are identified: W—walking, WA—walking with abdomen on surface, R—resting, B—biting, AOH—placing abdomen over the bite hole and OVI—oviposition. Comparison of host acceptance behaviours on Brassica napus L., Brassica juncea (L.) Czern, Brassica nigra (L.) Koch and Sinapis alba L. showed that S. alba was accepted as a host only after a long exposure to the plant. Behaviour on the Brassica species was similar, however on B. nigra beetles spent a high proportion of time actually ovipositing. We conclude that important cues for oviposition are located both on the bud surface and inside the bud.     

Fixation of 14CO2 in tissue cultured red raspberry prior to and after transfer to soil

The ¹⁴CO₂ uptake of an aseptically cultured red raspberry clone (Rubus ideaus L.) was examined prior to and after transfer to soil. Individual leaves of transplants, both persistent from culture and new ones, were tested 5 weeks after transplant for ¹⁴CO₂ uptake capability. Transplant leaves of successive weekly age classes took up ¹⁴CO₂ at increasing rates per unit area, displaying a spectrum of photosynthetic competence from low levels close to that of leaves from culture, to that of control plants. This is illustrative of acclimatization to the soil environment and was related to transplant light intensity.     

The role of glucosinolates and their hydrolysis products in oviposition and host-plant finding by cabbage webworm, Hellula undalis

The cabbage webworm, Hellula undalis (Fabricius) (Lepidoptera: Pyralidae), a tropical pest on crucifers (Brassicaceae), differentiated among host-plant species for oviposition in laboratory and field tests. White mustard, Sinapis alba (L.) var. Selinda, was the preferred host-plant, followed by Brassica juncea (L.) Czern. et. Coss var. Canadian brown mustard, and pak-choi, Brassica campestris L. ssp. chinensis var. Joi Choi, Black Behi and Bai Tsai. Glucosinolates (GS), secondary plant compounds characteristic to the Cruciferae plant family, and their breakdown products were analyzed by using HPLC and GC-MS-techniques. Species differed in GS composition and concentration. Content of GS was highest in S. alba with progressively lower contents detected in B. juncea and B. chinensis. The aromatic GS, 4-hydroxybenzyl-GS and benzyl-GS, were detected in S. alba. In B. juncea the alkenyl GS, allyl-GS, dominated, whereas in varieties of B. chinensis indolyl and alkenyl GS predominated. Oviposition of H. undalis females on the non-host-plant Vigna unguiculata ssp. sesquipedalis (L.) Fruwirth was stimulated by application of GS extracts from the crucifer species; the extract from S. alba was preferred, followed by extracts from B. juncea and B. chinensis. Hydrolysis of GS in the plant extract from B. chinensis causes loss of the oviposition stimulatory effect of the extract. Application of the GS, allyl-GS, and benzyl-GS also stimulated oviposition by H. undalis. Significantly more eggs were laid on leaves treated with the aromatic GS, benzyl-GS, than with the alkenyl GS, allyl-GS. Host-plant odor attracted H. undalis females but not males, in behavioral assays conducted in a Y-tube olfactometer. Low concentrations of the GS hydrolysis product, allyl-isothiocyanate, induced anemotaxis of females, but a high concentration of allyl-isothiocyanate was repellent. Oviposition by H. undalis females was not stimulated by host-plant volatiles. Females laid eggs on inserted traps and the walls of the Y-tube regardless of presence or absence of host-plant odor. The relevance of these results in the context of crucifer-insect interactions is discussed.     

The cation-efflux transporter BjCET2 mediates zinc and cadmium accumulation in <Emphasis Type="Italic">Brassica juncea</Emphasis> L. leaves

Brassica juncea L. is a Zn/Cd accumulator. To determine the physiological basis of its metal accumulation phenotype, the functional properties and role of the metal efflux transporter BjCET2 were investigated using transgenic technology. Heterologous expression of BjCET2 in the double mutant yeast strain Δzrc1Δcot1 enhanced the metal tolerance of the yeast strain and led to decrease in Zn or Cd accumulation. Detection of green fluorescence from green fluorescent protein (GFP) in the root tip of transgenic tobacco further revealed that BjCET2::GFP is localized at the plasma membrane. Semi-quantitative RT-PCR analysis showed that BjCET2 was most abundant in the root and was weakly expressed in the stem and leaves. The expression of BjCET2 was up-regulated by heavy metals. However, exposure to low temperature, salt and drought did not affect the expression of BjCET2. Overexpression of BjCET2 in transgenic B. juncea plants conferred heavy metal tolerance and increased Cd/Zn accumulation in the leaves. BjCET2-deficient B. juncea mediated by antisense RNA resulted in hypersensitivity to heavy metals and decreased Zn/Cd accumulation in the plants. These results suggest that the heavy metal efflux of BjCET2 plays important roles in the metal tolerance of B. juncea and in Zn/Cd accumulation in B. juncea.     

Efficient <Emphasis Type="Italic">Agrobacterium-</Emphasis>mediated genetic transformation of oilseed mustard [<Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) Czern.] using leaf piece explants

Leaf piece explants of five Brassica juncea (L.) Czern. cultivars were transformed with an Agrobacterium tumefaciens strain EHA105 harboring the plasmid pCAMBIA1301, which contains the β-glucuronidase (uidA) and hygromycin phosphotransferase (hpt) genes under the control of cauliflower mosaic virus 35S (CaMV35S) promoter. Transgenic plants were regenerated on Murashige and Skoog (MS) medium fortified with 8.87 μM 6-benzylaminopurine, 0.22 μM 2,4-dichlorophenoxyacetic acid, and 20 μM silver nitrate in the presence of 30 mg/l hygromycin. When co-culture took place in the presence of 100 μM acetosyringone, the efficiency of stable transformation was found to be approximately 19% in the T ₀ generation, with the transgenic plants and their progeny showing constitutive GUS expression in different plant organs. Southern blot hybridization of uidA and hpt genes confirmed transgene integration within the genome of transformed plants of each cultivar. Inheritance of hpt gene for single copy T-DNA inserts showed a 3:1 pattern of Mendelian segregation in progeny plants through germination of T ₁ seeds on MS medium containing 30 mg/l hygromycin. The protocol described here reports superior transformation efficiency over previously published protocols and should contribute to enhanced biotechnology applications in B. juncea.     

Free proline accumulation in drought-stressed plants

Summary Free-proline accumulation was measured in leaves of intact wheat (Triticum vulgare L. cv. Kalyan Sona), plantago (Plantago ovata Forsk-Isabgool), papavar (Papaver somnifera L. Opium poppy) and mustard (Brassica juncea L. var. Varuna) grown in the field with low to high field water content and thus they were subjected to water stress. Leaf water deficit in percentage was used to determine the degree of stress at the time of proline anlysis.Free proline content was higher in mustard leaves as compared to wheat, plantago and papavar leaves. Water stress enhances the proline content but at same water deficit level the content differ in the leaves of the plants studied.     

Putrescine Effect on Nitrate Reductase Activity, Organic Nitrogen, Protein, and Growth in Heavy Metal and Salinity Stressed Mustard Seedlings

Putrescine effect on nitrate reductase activity, organic nitrogen and protein contents, and plant growth under Cd or Pb (0.1 – 2 mM) and salinity (5 and 100 mM NaCl) stresses was examined in Indian mustard (Brassica juncea L. cv. RH-30) seedlings. Cd or Pb and salinity inhibited nitrate reductase activity and decreased organic nitrogen and protein contents in leaf tissue. The increased nitrate reductase activity induced by putrescine was correlated with increased organic nitrogen and protein contents and growth of plants.     

Activities of Carbonic Anhydrase and Ribulose-1,5-Bisphosphate Carboxylase,and Dry Mass Accumulation in Brassica juncea following Defoliation

The effect of 30 % defoliation of shaded leaves in lower layers of plant was studied on activities of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase (RuBPC), leaf dry mass per unit leaf area, and plant dry mass of mustard (Brassica juncea). Removal of 30 % of leaves resulted in increased CA and RuBPC activities of leaves, and leaf and plant dry masses.     

Effect of 28-homobrassinolide treatment on nickel toxicity in <Emphasis Type="Italic">Brassica juncea</Emphasis>

Plants of Brassica juncea L. cv. T-59 were supplied with 50 or 100 μM nickel (Ni₅₀, Ni₁₀₀) at 10 d after sowing (DAS), and sprayed with 28-homobrassinolide (HBR) at 20 DAS. The plants treated with Ni alone exhibited reduced growth, net photosynthetic rate, content of chlorophyll, and the activities of nitrate reductase (E.C.1.6.6.1) and carbonic anhydrase (E.C. 4.2.1.1) at observed 40 DAS, whereas, the contents of peroxidase (PER), catalase (CAT), and proline were increased. However, the spray of HBR partially neutralized the toxic effect of Ni on most of the parameters. Moreover, the treatment of HBR in association with either of the Ni concentration boosted the contents of PER and CAT in leaves and that of proline both in leaves and roots.     

The relationship between phosphate status and photosynthesis in leaves

Spinach (Spinacia oleracea L.) and barley (Hordeum vulgare L.) were grown in hydroponic culture with varying levels of orthophosphate (Pi). When leaves were fed with 20 mmol·l^–1 Pi at low CO₂ concentrations, a temporary increase of CO₂ uptake was observed in Pi-deficient leaves but not in those from plants grown at 1 mmol·l^–1 Pi. At high concentrations of CO₂ (at 21% or 2% O₂) the Pi-induced stimulation of CO₂ uptake was pronounced in the Pi-deficient leaves. The contents of phosphorylated metabolites in the leaves decreased as a result of Pi deficiency but were restored by Pi feeding. These results demonstrate that there is an appreciable capacity for rapid Pi uptake by leaf mesophyll cells and show that the effects of long-term phosphate deficiency on photosynthesis may be reversed (at least temporarily) within minutes by feeding with Pi.Abbreviation Pi orthophosphate     

Ethoxyzolamide repression of the low photorespiration state in two submersed angiosperms

Net photosynthesis in the submersed angiosperms Myriophyllum spicatum L. and Hydrilla verticillata (L.f.) Royal was inhibited by 21% O₂, but the degree of inhibition was greater for plants in the high than in the low photorespiratory state. Increasing the CO₂ concentration from 50 through 2,500 l l^-1 decreased the O₂ inhibition of the high-photorespiration plants in a competitive manner, but it had no effect on the O₂ inhibition of plants in the low photorespiratory state. Carbonic-anhydrase activity increased by almost threefold with the induction of the low photorespiratory state. Ethoxyzolamide, an inhibitor of carbonic anhydrase, reduced the net photosynthesis of low-photorespiration Myriophyllum and Hydrilla plants by 40%, but their dark respiration was unaffected. This ethoxyzolamide inhibition of net photosynthesis exhibited a competitive response to CO₂ concentration, resulting in a decrease in the apparent affinity of photosynthesis for CO₂. The net photosynthesis of plants in the high photorespiratory state was inhibited only slightly by ethoxyzolamide, and this inhibition was independent of the CO₂ level. Ethoxyzolamide treatment caused an increase in the O₂ inhibition of net photosynthesis of plants in the low photorespiratory state. Ethoxyzolamide increased the low CO₂ compensation points of low-photorespiration Myriophyllum and Hydrilla, but the values for the high-photorespiration plants were unchanged. In comparison, the CO₂ compensation points of the terrestrial plants Sorghum bicolor (C₄), Moricandia arvensis (C₃-C₄ intermediate) and Nicotiana tabacum (C₃) were unaltered by ethoxyzolamide treatment. These data indicate that the low photorespiratory state in Myriophyllum and Hydrilla is repressed by ethoxyzolamide treatment, thus implicating carbonic anhydrase as a component of the photorespiration-reducing mechanism in these plants. The competitive interaction of CO₂ with ethoxyzolamide provides evidence that the low photorespiratory state in submersed angiosperms is the result of some type or types of CO₂ concentrating mechanism. In Myriophyllum it may be via bicarbonate utilization, but in Hydrilla it probably takes the form of an inducible C₄-type system.Abbreviations PEP phosphoenolpyruvate - RuBP ribulose bisphosphate