Pod Maturity and Seed Germination of Blue Ternate (Clitoria ternatea L.)
Lorelyn Joy N. Turnos1*
1 University of Southern Mindanao, Kabacan, Cotabato, Philippines
*Corresponding Author: [email protected]
Accepted: 15 October 2021 | Published: 1 November 2021
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Abstract: Harvesting of seeds at proper stage of maturity is very essential to attain better seed quality. Excellent seed performance could be characterized by the seed viability and vigor, as well as their actual performance in the field. The seed viability of different varieties of Clitoria ternatea, commonly known as blue ternate plants, of five different pod maturities (1 – 100% green pods; 2 - 50% green + 50% brown pods; 3 – 100% light brown pods; 4 – 100% brown pods; 5 – 100% over-mature, twisted brown pods) was evaluated in this study. The study was carried out in a Split Plot Design arranged in Randomized Complete Block Design with four replications. This was conducted at the University of Southern Mindanao, Kabacan, Cotabato, Philippines from February to May 2020. Pod maturity based on the visual color of the pods significantly influenced seed germination. A 100% uniform color of both light to brown pods is a good indicator of higher germination rate. Seeds from over-mature pods with shrivelled and twisted conditions can still germinate but with lower germination percentage rate. The results also imply that even blue ternate pods are still green in color, as long as the seeds are already black, these seeds were already capable of germination, however, at lower germination rate compared to pods which are already brown.
Keywords: Clitoria, blue ternate, pod maturity, seed germination
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1. Introduction
Successful seed production is highly dependent on the detection and implication of optimal time of harvesting. Stage of maturity at harvest significantly influences the quality of seeds (Demir et al., 2008). Harvesting the pods too early may cause poor seed germination rate, high seed dormancy, low yield and quality, because of the partial development of essential seed structures (Elias & Copeland, 2001; Ekpong & Sukprakarn, 2008). Hence, stage of pod maturity at harvest affects seed yield, dormancy as well as seed viability and germination. Harvesting the pods too late may also increase the shattering risk and may affect the quality of the seeds primarily due to ageing. Moreover, adverse environmental condition such as raining may result in seed sprouting on mother plants (Wang et al., 2008; Elias & Copeland, 2001).
At the end of seed filling period (Tekrony & Egli, 1997) or slightly after this phase (Lehner et al., 2006), maximum seed quality may be achieved. The end of seed filling phase is described as physiological maturity (Harington, 1972) or mass maturity (Ellis & Pieta Filho, 1992). This study was conducted to evaluate the impact of pod maturity of different varieties of Clitoria on the
germination of the seeds. This is necessary to determine the appropriate time for harvest and seed quality improvement of the said crop.
In as early as 1950s, studies on Clitoria ternatea sought to elucidate the phytochemical composition, pharmacological activities and active constituents of the crop (Morita et al., 1976).
Commonly known as butterfly pea, it is a perennial herbaceous plant from the Fabaceae family.
The crop has attracted a lot of interest as it has potential applications both in modern medicine and agriculture, and as a source of antioxidants and natural food colorants. As a fast summer-growing legume, it can cover the soil within no more than 30 to 40 days after sowing and yield mature pods within 110 to 150 days. It has been cultivated as a forage and fodder crop, and has been widely used in traditional medicine, particularly as a supplement in enhancing cognitive functions and alleviate symptoms of numerous ailments like fever, pain, inflammation and diabetes (Mukherjee et al., 2008).
The study was laid out in a Split Plot Design arranged in Randomized Complete Block Design with four replications, and was conducted at the University of Southern Mindanao, Kabacan, Cotabato, Philippines from February to May 2020.
2. Literature Review
Harvesting of pods is more ideal when immediately done after physiological maturity, wherein seeds attained the maximum dry matter accumulation, high vigor levels, high rate of germination (Guiamaraes et al., 2012). Various researchers (Sedyama, 2013; Forti et al., 2013; Kehl et al., 2016; Rigo et al., 2018) revealed that delayed harvesting may reduce germination and vigor of the seeds. Therefore, there is a need to identify proper stage of maturity in which the pods or the seeds can be harvested without reducing vigor and viability in order to maximize yield and optimize the quality of harvest.
Gast (1992) concluded that harvesting at proper maturity stage is the most critical stage in postharvest system which may lead to very serious losses, both quantitatively and qualitatively.
Moreover, Salunkhe and Desai (1984) stated that beans should be harvested prior to full grown stage of the pods while the seeds are still small. He added that majority of bean cultivars become stringy and tough when left on the lant until the seed develops to a considerable size. Champa et al. (2008) also observed that the maturity of Phaseolus beans can be achieved at 12 to 15 days after fruit setting (DAFS) under dry zone conditions (28±2oC temperature and 69 - 78% relative humidity).
The study of Cerna and Beaver (1989) revealed that physiological maturity of a community of indeterminate bean plants occurred when most pods were brown; that is, later than the occurrence of PM suggested by other researchers (CIAT, 1982; Izquierdo & Hosfield, 1981; Lebaron, 1974;
Yourstone, 1988).
Germination rate and seedling emergence can be significantly decreased due to low seed quality, leading to poor stand field establishment and eventually yield loss in many crops, including garden pea (Hampton and Scott, 1982), corn (Moreno-Martinez et al., 1998), barley (Samara and Al- Kofahi, 2008), wheat (Ganguli and Sen-Mandi, 1990) and cotton (Iqbal et al., 2002). Hence, it is
important to examine and identify appropriate techniques for the production of high quality seeds from different crops.
3. Discussion and Conclusion
Harvesting of seeds at proper stage of maturation is very essential to attain better seed quality.
Excellent seed performance could be characterized by the seed viability and vigor, as well as their actual performance in the field. Timing of harvest is very critical because reduction of seed quality could be due to seed immaturity and weathering. As mentioned by Seshu and Dadlani (1989), the major aspects of seed quality are: genetic and physical maturity, high germination and vigor, and absence of seed-borne pests.
As part of this study, in order to evaluate the physiological maturity of Clitoria, a field trial was done using Clitoria pods at different stages of maturity and different varieties. Seed viability of five different maturities (Figure 1) of the pods was evaluated. Moreover, five different varieties of Clitoria, specifically two blue double-layered varieties, one White-colored single, one Blue- colored single and one Violet-colored single variety as the test plants.
As presented in Table 1, the interaction of the maturity of the pods and Clitoria varieties did not significantly influence the germination rate of the seeds. However, statistical analysis revealed that pod maturity alone and the Clitoria varieties resulted in significant seed germination.
Figure 1: Different stages of pod maturity of Clitoria ternatea.
Legend:
M1 - 100% green pods (with black seeds) M2 - 50% green + 50% brown pods
M3 - 100% light brown pods M4 - 100% brown pods
M5 - 100% over-mature and shrivelled brown pods
Table 1: Percentage (%) seed germination of different Clitoria varieties as influenced by various pod maturity stages at 21 days after sowing. University of Southern Mindanao, Kabacan, Cotabato, Philippines. 2020.
Maturity Stage Blue-double (NC)
Blue-double (DC)
White-single (DC)
White-single (NC)
Blue-single (NC)
Mean1/
M1 61.00 60.25 47.50 53.50 64.00 57.25b
M2 85.25 80.50 68.25 73.00 87.50 78.90a
M3 84.00 82.75 71.50 88.00 86.50 82.55a
M4 88.75 87.25 76.00 82.50 89.50 84.80a
M5 61.75 56.25 53.75 70.75 55.00 59.50b
Mean2/ 76.15a 73.40a 63.40b 73.55a 76.50a
1/a - Meansainatheasameacolumnawithacommonaletterasuperscriptsaareanotasignificantly differentaata1%alevel (Tukey’s Test).
2/ - Meansainatheasamearowawithacommonaletterasuperscriptsaareanotasignificantly differentaata1%alevel (Tukey’s Test).
Maturity 0.000
Variety 0.000
Interaction 0.053
CV (%) a 13.34
b 9.80
Legend:
North Cotabato (NC), Davao City (DC), South Cotabato (SC) Pod maturity stages:
M1 - 100% green pods (with black seeds) M2 - 50% green + 50% brown pods
M3 - 100% light brown pods M4 - 100% brown pods
M5 - 100% over-matured and shrivelled brown pods
In terms of the maturity stage of the pods, it was noted that maturity stage 4 (100% brown pods) resulted with the highest seed germination of 84.80%. This was found comparable with M3 (100%
light brown pods) and M2 (50% green + 50% brown-colored pods) with means of 82.55 and 78.90%, respectively.
Seed germination of all Clitoria varieties at early stage (maturity stage 1 – pods in green color with black seeds) of pod maturity obtained the lowest seed germination of 57.25%. On the other hand, seed viability started to decrease with 59.50% germination rate at maturity stage 5 (over-matured, shrivelled brown pods). In terms of varietal differences, seed germination of all varieties, except for the white single variety (63.40%), was found statistically comparable having a range of 73.40 to 76.50%.
The results imply that even though the blue ternate pods are still green, as long as the seeds are already black, the seeds were already capable of germination, however at lower germination rate compared to seeds from pods which are already brown. A 100% or uniform color light brown to brown pods is a good indicator of higher germination rate. Moreover, seeds from an over-mature pods with shrivelled and twisted conditions can still germinate but at lower germination percentage rate.
This is in affirmation on the findings of Kumar et al. (2002) that yield and quality of seeds are highly dependent on the crop’s maturity stage. Moreover, a very high moisture may increase possibilities of seed infection due to various pathogens, whereas harvesting at low moisture content will contribute to the seed’s susceptibility to mechanical damages (Yadav et al., 2005).
Summary
The results of the study can be summarized as follow:
a) Pod maturity based on the visual color of the pods significantly affected the germination of seeds. A 100% uniform color of both light brown (Maturity Stage 4) to brown pods (Maturity Stage 3) is a good indicator of higher germination rate.
b) Blue ternate pods which are still green but seeds are already black are already viable, however at lower germination rate as compared to seeds from brown pods. Seeds from over-mature pods with shrivelled and twisted conditions can still germinate but at lower germination percentage rate.
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