Abstract: A pot experiment was conducted at NWFP Agricultural University Peshawar Pakistan during 1998 to study the effect of different salinity levels on pearl millet at early growth stage. The experimental results revealed that the performance of various millet varieties evaluated was significantly different for shoot fresh weight, shoot dry weight, shoot Na+ content and shoot K+ concentration at two growth periods i.e., 15 and 30 days after salt application. Millet genotype ICMV-94151 was found to have maximum shoot fresh weight, shoot dry weight, shoot K+ concentration and lowest shoot Na+ at 15 and 30 days after salt application. Increasing salinity levels had significantly reduced shoot fresh weight, shoot dry weight and shoot K+ at both growth stages. Three millet cultivars ICMV-95151, ICMV-95490 and Gana white performed significantly better than the other when exposed to different levels of salinity.
Introduction
Pearl millet is an important crop of the world. It produces greater quantity of grains than other cereal under conditions of scanty rain fall, infertile soil and intense heat. It requires a short growing season. One of the most important constraint in increasing the production of millet and bringing more area under this crop is soil salinity/sodicity in these areas. Keeping in view the importance of Pearlmillet in our agricultural system, the present experiment was conducted to screen out various varieties of millet under different salinity for different physiological parameters. Various physiological phenomena are related to salt tolerance in plants (Rowers et al., 1977; Yeo and Flowers, 1984; Slam et al., 1993b). Plants can overcome the toxic effect of excessive ions through different physiological traits such as compartmentation, synthesis and accumulation of compatible solutes in cytoplasm, vigor to provide dilution of salt concentration by growth, efficient exclusion of Na+ (Gorham et al., 1985; Slam et al., 1991, 1993b). Munns et al. (1982), Rashid (1986) and Slam et al. (1993b) reported a positive correlation between Na+ exclusion and relative salt tolerance of many crops.
Materials and Methods
In order to study the effect of different salinity levels on pearlmillet at early growth stages, a pot experiment was conducted at NWFP Agricultural University in Randomized Complete Block Design (CRD) with three Replications. Eight Pearlmillet varieties (Gick-93771, ICMV-95490, ICMV-94151, Bari-MS-22-95, 85-2, Ghana white, Togo and V-94-1) were screened at five different salinity levels (0,4,8,12 and 16 dS m–1). Each pot (30×35 cm) was filled with 20 kg of soil. Seeds were sown in each pot at uniform depth (2 cm) and after complete germination emergence, thinning was done and seven plants were maintained in each pot. A recommended fertilizer dose of 100-50-0 NPK kg ha–1 was applied to each pot. Plants were subjected to the proposed salinity levels through irrigation water by the addition of salt in increment 30 days after emergence. Data was recorded on shoot fresh weight, shoot dry weight, shoot Na+ content and shoot K+ concentration at two different growth stages i.e., 15 and 30 days after salt application. Data was subjected to analysis of variance procedure according to CRD and upon obtaining significant differences least significant difference (LSD) test was applied for the comparison of treatment means.
Results and Discussion
Data recorded on shoot freshweightat15and30 days after salt applicationg is presented inTable 1.Statistical analysis of the data revealed that shoot fresh weight was significantly (p<0.05) affected by various varieties and different salinity levels at 15 and 30 days after salt application.
| Table 1: | Shoot fresh weight (g) of various millet varieties after different days of salt application |
After 15 days of salt application, After 30 days of salt application, LSD(0.05) value for varieties = 0.5777, LSD(0.05) value for varieties = 0.4548 LSD(0.05) value for salinity levels = 0.4567, LSD(0.05) value for salinity levels = 0.3594, LSD(0.05) for interaction = 1.016 | |
| Table 2: | Shoot dry weight(g) of various millet varieties after different dais of salt application |
| Table 3: | Shoot Na+ concentration (rrreq/g dry weight) of various millet varieties at different days after salt application |
| Table 4: | Shoot K* concentration(mag/g dry weight) of various millet varieties at different days after salt application |
It can be evident from the data presented in Table 1 that ICMV-94151 produced maximum shoot fresh weight (12.31 and 21.18 g) while Togo produced minimum shoot fresh weight (8.83 and 17.48 g) at both growth stages. Mean values of the data also showed that shoot fresh weight was progressively decreased with increasing salinity, maximum decreased being noticed at high salinity level (i. e., 16 dS m–1). Similarly ICMV-94151 at control produced maximum shoot fresh weight, while Togo when exposed to high salinity levels produced minimum shoot fresh weight. This decrease in shoot fresh weight by high salinity may be due to water and nutrient stress and toxic effect of high concentration of Na+ in the soil medium which in turn reduced photosynthesis (Carlos and Bingham, 1973; Kawasaki et al., 1983). Similar results are also supported by Chhlppa et al. (1992) who found that fresh shoot decreased with increasing salinity. Similarly, Malibari et al. (1993) reported decrease in growth with an increase in salinity. Shoot dry weight data was also recorded at two growth stages i.e. 15 and 30 days after salt application (Table 2). Analysis of the data revealed that varieties and salinity levels had significantly (p<0.05) affected shoot dry weight at 15 and 30 days after salt application whereas the effect of interaction was significant at 30 days after salt application. The data manifested that ICMV-94151 recorded maximum shoot dry weight (4 and 6.14 g), while minimum shoot dry weight (3.45 and 5.34 g) was noted from Togo. Mean values of the data also showed that plants exposed to higher salinity levels ( i.e., 18 dS m–1) produced minimum shoot dry weight at both growth stages as compared with other treatments. Similarly, 1CMV-9415 produced more shoot dry weight at control while Toga when exposed to 18 dS m–1 produced minimum shoot dry weight at both growth stages i.e. 15 days and 30 days salt application. This decrease in shoot dry weight may be due to the fact that Na+ concentration may have caused physical damage to the root system and have decreased their ability to absorb water and nutrient which has resulted in stunted growth.
These results are supported by Ashraf and McNeilly (1992) and Onkware and Ochieng (1993) who reported significant decrease in shoot dry weight when exposed to salinity.
Table 3 presents data regarding shoot Na+ concentration recorded at 15 and 30 days after salt application. Statistical analysis of the data showed that shoot Na+ concentration was significantly (p<0.05) affected various varieties, different salinity levels and their interactions at both growth stages. Mean values of the data revealed that Togo had Maximum dry weight shoot Na+ (0.586 and 0.614 meq g–1), while ICMV-94151 recorded minimum dry weight shoot Na+ (0.490 and 0.482 meq g–1) at both 15 and 30 days after salt application. It can be inferred from the data that shoot Na+ content progressively increased with increasing salinity levels. Minimum Na+ concentration was obtained at control, while maximum at high salinity level (i.e., 16 dS m–1) at both growth stages. Similarly, data concerning varieties and salinity Interaction showed that ICMV-94151 accumulated less Na+ in their shoot when compared with other varieties exposed to different salinity levels. it has been observed by many researchers that salt exclusion is an important salinity tolerance mechanism. (Yeo and Flowers, 1984; Akita and Cabuaaly, 1990; Yeo, 1992; Slam et al., 1993a; Onkware, 1993). Table 4 shows data regarding shoot K+ concentration at 15 and 30 days after salt application respectively. Statistical application analysis of the data indicated that K+ was significantly (p<0.05) effected by various varieties and different salinity levels as well as their interaction. Mean values of the data exhibited that ICMV-94151 had maximum shoot K+ (1.314 and 1.363 meq g–1 dry weight) concentration while Togo accumulated minimum K+ in their shoot at both growth stages i.e., 15 and 30 days after salt application. It can also be seen from the data that plants exposed to high salinity levels accumulated less K+ in their shoot when compared with other treatments at 15 and 30 days after salt application. Similarly, mean values of the data presented in Table 4 also indicated that ICMV-94151 accumulated more IC in their shoot when exposed to different levels of salinity as compared to other varieties. Many researchers agreed that tolerant varieties maintained better K+ and K: Na in their tissue under saline conditions. Salt tolerant crops had their tissue relatively free from the toxic ion besides maintaining assured supply of K+ (Sharma, 1986). Maintenance of high K+ concentration and especially K: Na ratio are the major physiological character of salt tolerant plants (Slam et al., 1993b).