RESEARCH NEWS CURRENT SCIENCE, VOL. 99, NO. 3, 10 AUGUST 2010 274 Nano-agriculture – carbon nanotubes enhance tomato seed germination and plant growth C. Srinivasan and R. Saraswathi Agriculture is an area where new tech- nologies are often applied to improve the yield of crops. Genetically modified (GM) crops have received mixed reac- tions from the public, particularly the farmers. The recent approval of Bt - brinjal seeds by t he government triggered a lot of dissent among farmers and the public qu ickly pro mpting the government to withdraw its decision. (For a detailed discussion on Bt -brinjal, see ref. 1.) Nano-agricul ture involves the employ- ment of nanoparticles in agriculture with the ambition that these particles will im- part some beneficial effects to the crops. Carbon nanotubes (CNTs) have acquired an important status in nanotechnology due to their unique mechanical, elec- tronic and thermal properties, which have led to their exploitation in diverse applications such as sensors, flat panel displays, energy and gas storage 2 . Also, their application in drug delivery and medical diagnostics is being actively explored. The study on the effects of nanoparticles in plant science is a newly emerging area of research 3–5 . Recently, confocal fluorescence image studies have revealed the capacity of single- walled carbon nanotubes (SWNTs) to traverse across both the plant cell wall and cell membrane 6 . This study also pointed out that SWNTs can serve as effective nanotransporters to deliver DNA and small dye molecules into intact plant cells. There are also some reports on other nanoparticles as smart treat- ment-delivery systems in plants 7 . Com- pared to plant cell walls and membranes, the penetration of nanoparticles into seeds is expected to be difficult due to the significantly thick seed coat covering the whole seed. In spite of this anti- cipated hurdle, Khodakovskaya et al. 8 demonstrated that CNTs could effec- tively penetrate seed coat, thereby influ- encing the seed germination and plant growth. This study commendably esta- blished that exposure of seeds to CNTs resulted in the enhanced tomato seed germination and growth rate. The experi- ment involved placing sterile tomato seeds on standard agar Murashige and Skoog medium (MS medium) with different concentrations (10, 20 and 40 μg/ml) of added multi-walled carbon nanotubes (MWNTs) and also without nanotubes. It is amazing to note that the seeds placed in the MS medium with the given three concentrations of CNTs sprouted on the third day whereas the seeds in the control experiment (without CNTs) did not germinate in the same period (Figure 1 a). Also, in the next few days the germination rate in CNTs sup- plemented medium was significa ntly higher than that observed for the control sample (Figure 1 b). The germination percentage for seeds that were placed on regular medium averaged 71 in 20 days, whereas germination percentage of the seeds placed on medium supple- mented with CNTs (40 μg/ml) averaged 90 during the same period. Tomato plants grown in media sup- plemented with CNTs not only showed an increase in biomass but also possessed well-developed long stems compared to the control (Figure 2 b). However, the length of the roots was found to be the same in both cases (Figure 2 a) indicat- ing the absence of any toxic effects of CNTs on root development and root elongation in the concentration range studied. Khodakovskaya et al. 8 thus demonstrated that CNTs exposed seeds germinated up to two times faster than control seeds and the seedlings weighed more than twice as much as the untreated plants. These desirable effects possibly Figure 1. Effect of CNTs on tomato seed germination. a, Tomato seeds incubated dur- ing 3 days without (left) or with (right) CNTs on MS medium. b, Time of germination and germination percentages of seeds incubated with and without CNTs during 20 days. Re- printed with permission from Khodakovskaya et al. 8 . Copyright (2010) from American Chemical Society.