SCIENTIFIC CORRESPONDENCE CURRENT SCIENCE, VOL. 102, NO. 12, 25 JUNE 2012 1632 6. Lemna aequinoctialis Welw. Apont.: 578. 1859. Type: Angola; Prov. Luanda, Distr. Luanda; 1858, F. Welwitsch 206. Lecto, photo! STU; Isolecto, BM, G, K, ZT. (Landolt, 1986). Lemna angolensis Welw. ex Hegelm., J. Bot. 3: 112. 1865. Lemna paucicostata Hegelm., Lemnac. 139. t. 8. 1868. Lemna paucicostata var. membranacea Hegelm., Lemnac.: 141. 1868. Lemna trinervis (Austin ex Gray) Small, Fl. S.E.U.S. 230. 1903 pp. Lemna minima Blatt. & Hallb., J. Indian Bot. 2: 50. 1921. Lemna blatteri McCann, J. Bombay Nat. Hist. Soc. 43: 153. 1942. Lemna aoukikusa T. Beppu & Murata, Acta Phytotax. Geobot. 36: 55. 1985 (Figures 1 b, g and 2 c–e). Fronds light green, usually 1–3 together, oblong or ovate or orbicular, 2–5 × 0.13–0.09 mm, asymmetrical; two distinct papulae on the dorsal surface; nodal (where the veins converge) papil- lae smaller than apical one. Roots one; root sheath winged, ca. 0.01 × 0.02 mm. Inflorescence on two lateral pouches. Male flowers two, ca. 0.1 mm in length; anthers divaricate, bilocular, dehisce by transverse slit. Female flower composed of gynoecium; ca. 0.2 mm long; ovary globose, hyaline; style one, terminal. Fruit utricle. Distribution in India: throughout the country. Note: Though isolecto is said to be in BM (The Natural History Museum, Lon- don) and ZT (Edgenossische Technische Holochschule Zurich, Switzerland), the concerned databases of these herbaria do not show these types. But these types are included based on Landolt (l.c.). 1. Hooker, J. D., Flora of British India, L. Reeve and Co, London, 1893, vol. 6, pp. 556–558. 2. Prain, D., Bengal Plants 2, West New- man and Co, London, 1903, vol. 2, pp. 840–841. 3. Karthikeyan, S., Jain, S. K., Nayar, M. P. and Sanjappa, M., Florae Indicae Enu- meratio: Monocotyledonae, Botanical Survey of India, Kolkata, 1989, p. 87. 4. Cook, C. D. K., Aquatic and Wetland Plants of India, Oxford University Press, Oxford, UK, 1996, pp. 226–231. 5. Gray, S. F., Natural Arrangement of British Plants, According to their Rela- tion to Each Other, London, 1821, vol. 2, p. 729. 6. Hegelmaier, F., Die Lemnaceen. Eine monographische Untersuchung, Verlag von Wilhelm Engelmann, Leipzig, 1868. 7. Hegelmaier, F., Bot. Jahrb. Syst., Pflan- zengeshi. Pflanzengeogr., 1895, 21, 268– 305. 8. Engler, A., In Naturliche Pflanzenfami- lien (eds Engler, A. and Prantl, K.), Wilhelm Engelmann, Leipzig, 1889, vol. 2, pp. 154–164. 9. Ascherson, P. and Graebner, P., Synopsis mitterluropaischen Flora, Engelmann, Leipzig, 1904, vol. 2, pp. 390–397. 10. Ludwig, F., In Lebensgeschichte de Bliitenpflanzen Mitteleuropas (eds von Kirchner, O., Loew, E. and Schroeter, C.), Ulmer, Stuttgart, 1909, vol. 1, pp. 57–80. 11. Lawalree, A., Bull. Soc. Roy. Bot. Belg., 1945, 77, 27–38. 12. Hartog, Den, C. and Van der Plas, F., Blumea, 1970, 18, 355–368. 13. Landolt, E., Veroff. Geobot. Inst. Stiftung Rubel, 1986, 2. ACKNOWLEDGEMENTS. We thank the curators of BM (for L. gibba, L. minor and L. trisulca) and STU (for L. perpusilla and L. aequnoctialis) for images of the types; Prof. E. Landolt (ZT) for confirmation of identity of different collections, and the Director, BSI, Kolkata for facilities and fellowship to S.H. under the Flora of India programme. Received 29 August 2011; revised accepted 15 May 2012 SUMAN HALDER P. VENU* Botanical Survey of India, Central National Herbarium, Howrah 711 103, India *For correspondence. e-mail: pvenu.bsi@gmail.com Bt Cry toxin expression profile in selected Pakistani cotton genotypes Pakistan is ranked fourth among the top five cotton-producing countries in the world. About 70–80% of the cultivated area is under Bt cotton in Pakistan 1 . Boll- worm (Helicoverpa armigera) is the ma- jor pest of cotton 2 . It causes 31.73– 36.45% yield losses 3,4 and these are re- duced by heavy pesticide application. There has been a tremendous increase in the import and use of pesticides. Conse- quently, about 7.7 billion rupees is spent on pesticides every year 5 . Considering the total pesticide usage (94,265 metric tonnes in 2007–08), 70% is being used exclusively on cotton. In addition to be- ing a pollutant, pesticides are also haz- ardous to the farmers and livestock 1 . The large amount of money being spent on these chemicals can be avoided by plant- ing Bt cotton. From biosafety point of view, Bt bio- pesticides are better than chemical pesti- cides. Because the Bt toxins are highly specialized and have no negative effect on the environment 6 . The effectiveness of Bt cotton depends on the expression of insecticidal genes 7 and does not remain constant throughout the growing season 8 . The performance of Bt genes for control- ling target insect pests varies according to the cotton varieties 9 , age of the plant 10 , different parts of the plant 11 , types of gene and also the insertion sites of the gene into the DNA of target plants 12–14 . In Pakistan, the shift to Bt cotton was slow due to non-existence of necessary infrastructure. Plant breeders developed Bt varieties using local genotypes through backcrossing with alien Bt cot- ton varieties having the Cry1Ac gene of non-patented event (MON531) in Paki- stan. In 2010, approximately 600,000 farmers cultivated Bt transgenic cotton varieties 15 . A study estimated that 81% and 90% were confirmed Bt varieties having only the Cry1Ac gene, in Sindh and Punjab provinces respectively 1 . The introduction of Bollgard-II event is expected soon as negotiations between the Government of Pakistan and Mon- santo, USA are in progress. To reduce the risk of resistance deve- lopment in target insect pests against Bt cotton, there is a need to understand the variations in efficiency of Bt genes and their mechanisms. For this, advanced bioassay techniques like ELISA have been used to measure the quantity variations in the Bt Cry (crystal) pro- teins 16 . The main objective of the present study was to quantify actual Bt toxin levels in cotton genotypes at the growth stages when they are attacked by boll- worm. The trend was also studied in plant parts (i.e. leaves and squares)