As can be seen in thisstudy, the enhancement of both Okra cultivars height and biomass (shoot androot) were increased after addition ofCNTs (50 and 100 mg/lit), theseobservations are in agreement with those of, Haghighi et al. (2014), whoexposed four vegetable species to different concentration of CNTs for two weeks.Use of CNTs stimulated water flux and uptake of ionic nutrients, may be explaining why growth is then stimulated, asTiwari et al. (2014) discovered for maize (Zea mays L.
). Liu et al. (2009) reported that CNTs can act as molecularchannels for water, also Xiuping Wang(2012) suggestedthat o-MWCNTs can signi?cantly enhance root dehydrogenase activity, which inturn enhances the ability of water uptake of the seedlings. A number of investigations have indicated that the expression of genes encoding an aquaporin protein considerably upregulated in plant cells exposed to multi-walled carbon nanotubes (Khodakovskaya,2012),but in this study when a 200 mg/lit of MWCNTs was used, emerald cultivar plantsshowed the least height and biomass (shoot and root). Different studies have reportedharmful effects of high MWCNT levels on grow of plant, for example, Haghighi (2014)reported that use of high level of CNTs decreased of fresh and dry weight and seedling length in radish and turnip, confirming the possibilityof a toxic effect resulting from a high level of CNTs. Parvin Begum (2012) indicated that high level ofMWNTs caused cell death and membrane damage in red spinach, lettuce, rice, and cucumber after 15 daysof exposure, who suggested that MWNTs may induce ROS formation, promoting cell death and electrolyte leakage in the different plant organs. Our results suggest a direct correlation between shoot androot growth parameter change and different concentration of MWCNTs in both cultivars of Okra plants. Also,we found that different cultivarS of Okra plants caused different responses toMWCNTs.
Plasticity in anatomicalcharacteristics of plants can help to their growth and development forsuccessful survival in environmentalhazards. Very little is known inrelation to the effects of MWCNTs on plants at theanatomical level. We evaluated the different indices anatomical andmorphological in shoot, root and leaf accordingto understand, durability who sections over it organs extra below consequencesconcerning MWCNT treatments. In this survey increasing of rootand shoot diameters in both cultivars that treatment by low and moderate MWCNTsmore affected by increasing of cortex thickness and central cylinder but inhigh concentration this parameter were more affected by cortexthickness increasing. Base of figure 4 prancheme cells size of cortex area havehigher thickness in high treatments. Shihan Yan and et al.
(2013) observed SWCNTs were appeared in the intercellular space and mainly present in the root cortex.Furthermore, studyof xylem and phloem diameters of shootshowed increasing of diameter in low (50 mg/lit) andmoderate (100 mg/lit) MWCNT treatments, but these parameters were decreased inhigh MWCNT level. Also, in root thisfact was determined that low treatments are cause of increasing of xylem diameter.
However root phloem diameters in MWCNTs treatment hadnot significant changes when compared to control plants in both cultivars.The tissue samples of Blackberry that treated by SWCNTs-COOH (4µg/ml) showed avascular cambium with mature xylem tissue and the presence of phloem cells, furthermorexylem vessels have developed completely and do not evidence the presence of cytoplasmic content (Dora Flores). Developedmetaxylem vessels in the stem play an important role for better transport ofwater and minerals (Steudle, 2000). It has suggested thatinsertion of carbon nanotubes into the plant tissues, causing plant development changes by regulating gene expression and related signal pathways as well as physiological effects S. Lin C.(2009). Mariya ( showed that MWCNTs affect the expressionof genes regulating cell division and cell wall extension in treated cells,resulted in faster growth than the unexposed control cells.
Khodakovskaya et al(2012)suggested the existence of different molecular mechanisms for cell growthactivation by the nanosized MWCNTs, who founded that the expression of genesessential for cell-wall assembly/cell growth, such as extension (NtLRX1), andfor the regulation of cell cycle progression, Cyc B significantly and rapidlyinduced by MWCNTs in tobacco cells.The study of leaf anatomy showed that leaf thickness underlow MWCNT treatments was increased, but this parameter was decreased byincreasing of MWCNT (moderate and high levels) treatments in both cultivars.Ourstudy indicated that mesophyll andspongy layer changes consist of increasingin low level and decreasing in moderate and high levels of MWCNTtreatments in both cultivars are similar.
Also, stomatasize was increased in low and moderate treatments in the bamia cultivar, however this parameterwas observed alone in low treatment in the emerald cultivar. Moreover, stomata index measurement showed that thisparameter was increased in moderate and high levels only in the emerald cultivar.Whereas carbon nanotubesincrease water absorption in plants, correlation between the content of theabsorbed water with increasing stomata index and stomata size may enhancestomata conductance that causegreater transpiration and water-use. According to Melo et al.(2007), the increase in stomatal density, coupled with the decrease in stomatalsize, would be an alternative to adequate supply of CO2 for photosynthesis, withoutexcessive water loss due to stomata with smaller pores. This may be anadaptation of plants in response totoxicity. Henggu ang Yuan (2011)reportedthat SWNTs can enter into intact Arabidopsis mesophyll cells, and then enterinto the organelles such as chloroplast, vacuole, mitochondria and nucleus.
So,it is possible that changes of mesophylland spongy layers of Okra plants have direct correlation with MWCNTs.