Key findings:

A two-factor experiment investigated the effects of growth regulators and soaking time on lentil seed germination and seedling vigor. Results showed that soaking seeds enhanced germination and seedling characteristics. GA or lemon application at medium concentrations increased all measured traits, particularly with longer soaking times. This study suggests potential for improving lentil seed germination and seedling growth with specific treatments.

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What is known and what is new?

Existing knowledge indicates that seed soaking can improve germination and seedling vigor in various crops. This study adds to the existing knowledge by specifically evaluating lentil seeds and the effects of growth regulators on germination indices and seedling vigor. The finding that soaking lentil seeds with medium concentrations of growth regulators can enhance germination and seedling growth is a novel contribution to lentil seed treatment strategies.

What is the implication, and what should change now?

The implication of this study is that farmers and researchers can use seed soaking with medium concentrations of growth regulators to enhance lentil seed germination and seedling growth. This practice could lead to improved crop establishment and ultimately higher yields. Agricultural practices should consider incorporating this treatment strategy to optimize lentil production. Further research could explore different growth regulators and their effects on lentil germination and growth in various conditions.

Poor germination and subsequent establishment of different pulse seed is a general problem in grain pulse production. Lentil, (lens esculenta) of family Fabaceae beans) is important legume crops in Sudan because of their importance in food, feed, and cropping system. It contains about twice as much protein as cereals. It also contains amino acid lysine which is generally deficient in food grains [1]. Seed Germination is the sum of events beginning with hydration and culminating with root emergence [2]. Among the stages of the plant life cycle, seed germination, seedling emergence and establishment are key processes in the survival and growth of plants [3]. The term plant growth regulators (PGRs) cover the broad category of organic compounds other than nutrients. The impact of PGRs in manipulating physiological processes in crop production include germination, vigor, nutrient uptake from soil, photosynthesis, respiration, partitioning of assimilate, growth suppression, defoliation and postharvest ripening [4,5]. Plant growth regulators such as GA and mechanical scarification such as soaking in water have been recommended to break dormancy and enhance germination. On the other hand, soaking in water treatments have been reported to enhance germination of hard coated seeds by elevating water and O2 permeability of the testa [6]. Incorporation of plant growth regulators, particularly gibbralic acid GA3, during re-soaking, priming and other pre-sowing treatments in many vegetables crops has improved seed performance [7]. The strong inhibitory effect of the seed coat on seed germination may be caused by several possible mechanisms, including mechanical constraint, prevention of water and oxygen uptake, and retention or production of chemical inhibitors [8]. The integument breaking or softening, for instance, is needed to remove dormancy imposed by seed coat hardness or impermeability. However, it is very difficult to use mechanical scarification to break the hard seed coat of A. cyclophyllon. There are evidences that different natural and synthetic growth regulators improve seed germination and seedling vigor of many crops [9,10]. These growth regulators may be of natural origin or synthetic. The growth regulators both from organic (Emblicaofficinalis, lemon, etc.) and inorganic sources along with some traditional growth regulators could be tried to increase the germination and vigour of different pulse seeds.

Therefore, chemical scarification (softening the hard seed coat with (cetric acid of lemon juice), soaking in water for specific hours and using of GA3 will be used to remove exogenous dormancy. Improvement in germination capability and increasing seed vigor might be one option to make the growing pulse seedling more competitive with those of weeds. These growth regulators may be of natural origin or synthetic. Works regarding the effect of growth regulators on pulse seed germination are very limited worldwide and are either lacking or scanty under Sudan condition. The proposed investigation will be undertaken to find out the effect of varying concentrations of different natural and synthetic growth regulators under soaking time to increase the seed germination and evaluate germination indices on lentil (lens esculenta).

Experiment Layout and Treatments

A two-factor experiment  was laid  out in  a randomized complete  blocks design  (RCBD) during 2018\2019 winter season in  Demonstration  Farm of Faculty  of Agriculture,  Kassala  University at Halfa  Elgadidah to evaluate effect of growth  regulator  (synthetic and natural)  on germination indices and  vigor of  Pigeon pea  and Lentil  seeds  under two soaking  time A15-cm diameters –sized pots  were used  in  this study  filled  with soil  from the Demonstration  Farm's media for  germination bed. The growth regulators treatments are:

G0≡ control  without  any growth regulators, GA3 were  G30 ≡30,  G45≡ 45 ,G60    ≡  60 , G75≡ 75, G90 ≡ 90 and  G105  ≡105 p.p.m while lemon juice concentration  were  L2 ≡2 , L4≡ 4  and L6 ≡ 6%.

Germination Test

Fifteen seeds of Lentil were obtained from Agricultural Research corporation station Halfa Elgadidah randomly selected for each treatment of all experimental units. The seeds were hand dibbled to about three centimeters depth with a spacing of 5 centimeters. The seed bed was provided with adequate moisture to get good germination and seedling stand. The seedlings considered germination when emerged above the soil surface. Seed germination was recorded daily at a certain time.

Germination Attributes were measured as Follows:

Final germination percentage (FGP) [%] for every day starting after first day of seedling emerged until last day: was calculated as described by (Basra, S. M. A. et al., 2011) [11] using the following formula:

Final Number of Seedlings Emerged

FGP (%) =  -------------------------------------------------- x 100

Total Number of Seeds Sown

Mean Daily Germination (MDG)

This is an index of daily germination speed and calculated according to formed described by (Farooq, M. et al., 2006) [12]

MDG =

FGP: final germination percent d: test period.

Daily Germination Speed (DGS)

This index is converse of mean daily germination and calculated according to formula described by (Farooq, M. et al., 2006). [12]

DGS =

Seedling Root length (cm)

On the day of final count (12th day) five randomly selected normal seedlings in each treatment were used to measure root length. The length of root was measured from collar region to the tip of the main root and the average root length was expressed in centimeters.

Seedling Shoot Length (cm)

The shoot length of five randomly selected seedlings were used for measuring shoot length from collar region to the tip of primary leaf and the average shoot length were expressed in centimeters.

Seedling Dry Weight of Ten Seedlings (Mg)

Five  normal seedlings used for root and shoot length measurement from each treatment were kept in blotter paper packet and dried in hot air oven maintained at 750 C for 24 hours. The dried seedlings were cooled in a desiccators for 60 minutes, then seedlings was weighed in an electronic balance and the weight was expressed in mg as dry weight of five seedlings.

Vigor Index

The vigor index of seedlings was calculated by adopting the method suggested by (Basra, S. M. A. et al., 2011) [11] and expressed in whole number by using the below formula.

Vigor index = (FGP (%)) x[shoot length + root length (cm)]

Data was statistically analyzed according to RCBD of factorial trail using computer software package Statistics version10. Mean separation was worked out by the least significant differences at 5% level.

Increasing gibraline (G) level until 75 p.p.m significantly increased the FGP of lentil as compared to other G and L treatments (Table 1). Soaking time showed significant differences on FGP for Lentil seeds which gave maximum% for H6 treatment particularly with addition of G60, G75 and L6 growth regulators treatments (Table 1). The higher DGS values (0.23) was recorded due to application G90 treatments as compared to other growth regulator treatments. Soaking time did not significantly differences in DGS (Table 1). The greater values of DGS were recorded in G90H6, G90 H12and G75H6 treatments relative to the all treatments (Table 1).

Table 1: Final Germination % (FGP), Mean Daily Germination (MDG) Daily Germination Speed (DGS) and Vigor Index of Lentil Seedling

In table2, the highest MDG value (7.70) was recorded in (G6H6, G6H12, G75H12, G105H6 and L2H6) followed by L2, L4 treatments which recorded 7.34,7.23, respectively. The higher vigour indices were recorded in treatment with higher levels of growth regulators particularly with two level of soaking time. In this regard, soaking Lentil seeds for six hours with application of L6 growth regulators level significantly gave the higher vigour index values as compared to their relative treatments (Table1). Increasing growth regulators levels under longer time resulted in heavier seedlings weight of Lentil. The higher seedling dry weight (0.13) were recorded in L2H12 treatment (Table2). Also, the longer roots were recorded in (G45H12, L6H12, L4H12) treatments while G60, G90, L2 and L6 growth regulator treatments increased the length seedling of Lentil particularly under longer time of soaking.

Table 2: Mean Seedling Length (cm) Root Length (cm) and Seedling Dry Weight (g) of Lentil Seedling

The impact of plant growth regulators (PGRs) in manipulating physiological processes in crop production include germination vigour and growth suppression was well documented in corporation of plant growth regulators ,particularly gibbralic Acid  GA3  during re-soaking and other presowing treatment in many vegetables crop has improved seed performance. The increased of all germination indices resulted in this study due to application of GA growth regulator might be due to positive role of GA in activation of cytological enzymes which stimulates α -amylase enzyme that converts in soluble sugars and leaching out of the inhibitors as which in turn helps in breaking the seed dormancy as reported by (Babu, K. D. et al., 2010) [13]. Also gibberellins are associated with various plant growth and development processes such as stem, and root elongation and dry matter accumulation. Due to its role in increasing cell division, cell elongation and cell multiplication which might have replicated in to maximum seedling growth. This might explained the increased in seedling characters observed in this study due to application of GA. These results are in accordance with those reported by (Gawade, U. S. 2008; & Gholap, S. V. et al., 2000) [14,15]. The increase in root length at lower concentration of GA observed in this study agreed the past study reported by (Wittwer, S. H., & Bukovac, M. J. 1958) [16] who reported that GA3 at lower concentration initiate the growth of root where as higher concentration has little effect on root growth. The increase in vigour index obtained in this study might be due to increase aforementioned characters as result of application of GA because the vigour index of seedling is directly dependant on germination percentage and seedling length so, the later characters were higher and consequently increased vigour index reported by [17].

The role of natural growth regulators such as lemon juice as chemical scarification to break the hard seed coat case softening the coat was reported by (Anburani, A., & Shakila, A. 2010). This might explained the result obtained in this study while lemon juice at higher level of concentration increased the germination indices.  Also this result confirmed by those resulted by (Pulok, M. A. I. et al., 2014) [18].

The increased in the all germination characters observed in this study due to soaking seeds in water might be attributed to role of positive effect of water in enhancing germination of these seeds by either elevating water and oxygen permeability of testa as reported (Aydın, I., & Uzun, F. 2001; & Kathiresan, G., & Balasubramanian, T. N. 1995) [19,6]. Also, increased in germination percentage resulted in increase of other growth parameters because these characters were associated with each other’s. Seeds treated with growth regulator and soaking in water helped to increase germination behaviour indices and great vigour seedling of lentil. In conclusion, as a result, soaking seeds of Lentil with application of medium growth regulator concentrations could increase the seed germination indecencies and seedling growth characters.

Funding: No funding sources 

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee of University of Kassala

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