Plant material (leaf, straws etc.) were collected from the outskirts of PMAS-AAUR Rawalpindi, Pakistan. Aerosol smoke was produced by burning of semi dried plant material in a specially designed furnace and aerosol smoke was collected for further process.

Seeds of wheat (Triticum aestivum L.) varieties NARC-2011, Aas-2011, Pakistan-2013 and Glaxy-2013 were taken from National Agriculture Research Institute (NARC) Islamabad, Pakistan.

Seeds of all four wheat varieties were immersed in a 10% sodium hypochlorite solution for 10 min to ensure surface sterility [9] . Then all seeds were rinsed thoroughly with distilled water and hand dried lightly using blotting paper. After surface sterilization imbibition of seeds were done by immersing seeds in distilled water for 6 hr at 25˚C to get imbibed seeds. Other seeds were used as non-imbibed for further treatment.

The imbibed and non-imbibed seeds of wheat were treated with plant derived aerosol smoke for about 1hr to check its effect on germination and post germination expression of wheat seeds. The plant derived smoke was used in aerosol form rather than as dissolved in water such as in the form of smoke water.

Germination assay was done separately for both imbibed & non-imbibed seeds of wheat varieties. One piece of filter paper was put into each Petri dish, and 5 ml of distilled water was added. Treated seeds were then transferred onto the filter paper, in separate Petri dishes. Petri dishes were covered and sealed with tape, and placed in an incubator at 22˚C ± 4˚C. Germination counts were taken on a daily basis for 10 days. After 10 days root & shoot length was measured. Then, seed germination percentage, germination index, seedling vigor index was calculated, and seedling root and shoot length was also measured. Germination index was calculated using formula designed by ISTA [10] , and seedling vigor index was calculated by using equation designed by Abdulbaki and Anderson [11] .

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Each treatment was conducted with three replicates, and the results were presented as mean standard deviation. The statistical analysis of experimental data utilized the Student’s t-test. Each of the experimental values was compared to corresponding control.

Effect of plant derived smoke on germination response of non-imbibed and imbibed seeds of different wheat verities are shown in Figure 1 & Figure 2. Non-imbibed seeds treated with plant derived smoke showed best germination response as compared to imbibed seeds where germination response was very poor in all varieties. Germination percentage also varied from variety to variety. Maximum germination was recorded in Pak-13 (98 ± 0.6), Gla-13 (95 ± 0.6) and in NARC-11 (92 ± 2.31) where rate of germination was increased upto 3.3%, 3% and 4% as compared to their corresponding control. Plant derived smoke stimulate and promote germination response as it increase seed sensitivity to endogenous GA₄ [6] [17] - [19] and therefore enhance seed germination. Reduction in germination response was noticed in Aas-11 (88.3 ± 10.2) where both non-imbibed and imbibed seeds treated

*N.I seeds = Non-imbibed seeds.

with plant derived smoke failed to show pronounced effect. Sometimes plant derived smoke can negatively or positively affect germination [17] [20] [21] .

Smoke, however, not only influences germination but importantly it also stimulates seedling vigor (post-germinative growth) [12] [22] . In present investigation there were significant difference was noticed in germination index and seedling vigor index among different wheat varieties in response to plant derived smoke (Figure 3 & Figure 4). Non-imbibed seeds of Pak-13, Gla-13 and NARC-11 showed considerable increase in germination index and seedling vigor index as compared to imbibed seeds while Aas-11 show reduction in both non-imbibed

and imbibed seeds being treated with plant derived smoke. Baxter et al. [12] reported that the seedlings of Themeda triandra from smoke-treated seeds grew more vigorously without any abnormalities than untreated seeds. A similar effect was observed in species of Ericaceae and Asteraceae family [23] and in commercial maize (Zea mays) [7] . Plant derived smoke has a positive effect on seedling vigor [24] and favor high seedling establishment and may increase species diversity [25] - [27] .

To examine the effect of plant derived smoke on root shoot growth, both non-imbibed & imbibed seeds were incubated on Petri dishes with 5 ml distilled water after being treated with plant derived smoke for one hour time duration. Increase in root growth was seen in seedlings emerged from non-imbibed seeds treated with plant derived smoke as compared to imbibed seed where reduction in root length was noticed with respect to control (Figure 5 & Figure 6). Maximum root length was recorded in non-imbibed seeds of Pak-13 (13.1 mm), Aas-11 (10.6 mm) and Gla-13 (9.9 mm) where as imbibed seeds of all varieties did not show significant increase in root length. Number of studies have been reported a positive influence of plant derived smoke treatments on seedling growth and development of several crop plants, including celery [28] , lettuce [29] , okra [6] , tomato [30] , onion [31] , aubergine [32] , Brassica tornefortii [33] , pepper (Capsicum annuum L.) and salvia species [8] .

Shoot growth was also observed with the same treatment as applied for root growth to examine the effect of plant derived smoke on wheat growth. Non-imbibed seeds treated with plant derived smoke exhibited significant increase in shoot length while imbibed seeds showed comparable results in shoot length as compared to seedlings not treated with plant derived smoke. Remarkable increase in shoot length was observed in non-imbibed seeds of NARC-11 (12 mm) and Aas-11 (12.9 mm) and in imbibed seeds of NARC-11 (10.2 mm) and Gla-13 (11.3 mm) varieties after treatment with plant derived smoke. Zhou et al. [34] reported that plant derived smoke improves shoot growth in Isatis indigotica seedling. Seeds treated with plant derived smoke grow faster and has increased

vigor and fresh weight [22] [34] - [36] . Plant derived smoke treatments have great potential for use in horticulture and agriculture [24] [37] [38] .