Relations between drought-resistance and chlorophyll content of 25 local upland rice cultivals (oryza sativa L)

JOURNAL OF SCIENCE OF HNUE Natural Sci., 2010, Vol. 55, No. 6, pp. 161-168 RELATIONS BETWEEN DROUGHT-RESISTANCE AND CHLOROPHYLL CONTENT OF 25 LOCAL UPLAND RICE CULTIVALS (Oryza Sativa L.) Nguyen Thi Ngoc Lan(∗) and Chu Hoang Mau Thai Nguyen University of Education Nguyen Nhu Khanh Hanoi National University of Education (∗)E-mail: ntnl2008@gmail.com Abstract. Water retention ability of leave tissues of twenty five local upland rice cultivars (Oryza Sativa L.) was defined through the amount of water loss through different time frames. The results showed that the amount of water loss of leaf tissues of twenty five local upland rice cultivars through times: one hour, two hours, three hours, four hours, five hours and six hours had increased. Water loss of the same at the one-hour-time range 11.197% to 17.956%, up to six-hours-time the amount of water loss in rice varieties have reached a value of about 43.707% to 63.504%. Gb has the highest dehydration resistant and the lowest is Klk. Total chlorophyll content of rice varieties ranges from 1.496 to 1.962 mg/g leaving fresh weight and was ranged in order from high to low values of total chlorophyll content: Gb> Bsn> Md> Ln> Bcc> Kn > Ss> BCS> Nn> LTN> Mt> BLT> Km> Nro> Lo> Kk> BCT> Kp> Kt> Bic> KPL> Blx> Kld> KX> Klk. Gb still has the highest bond chlorophyll content in all three types (chlorophyll a, chlorophyll b, chlorophyll (a + b)) and Klk has the lowest. Total chlorophyll content, total bond chlorophyll and dehydration resistant of leaves have close, agreeable correlation. It can be based on the chlorophyll content in leaves to initially assess dehydration resistance of plants. Keywords: Upland Rice, Oryza Sativa L., chlorophyll, drought resistance, water retention. 1. Introduction One of the consequences of climatic change is increasing drought in many parts of the world including Vietnam. This is also the main cause promoting projects 161 Nguyen Thi Ngoc Lan, Chu Hoang Mau and Nguyen Nhu Khanh and research to develop drought-resistant crops with the best yield response to increasing demand of people while the water supply for agricultural production had decreased gradually [1, 5, 8, 9]. In particular, many researchers have focused on the identification of morphological characteristics and indicators of physiological biochemical characteristics of drought resistant plant varieties as characteristics of roots, leaves, abscisic acid content, concentration of potassium (K+), sugars, organic acids etc. (Le Tran Binh et al., 1998 [2]). Content of chlorophyll in leaves is not only an indicator of photosynthetic capability of plant tissue (Nageswara et al., 2001 [7]) but also the factor that di- rectly related to growth process of plants (Farquhar and Richards, 1984 [3]). When studying the relationship between water content and chlorophyll content of sesame (Sesamum indicum L.) in conditions of different water supplies, M. Hassanzadeh et al. (2009) [4] suggested that it may be based on the content of chlorophyll b and total chlorophyll to select varieties with drought tolerance and high yield. The research of Oukarroum Abdallah et al. (2007) [9] on the effect of drought stress and re-watering on barley (Hordeum vulgare L.) showed that chlorophyll fluorescence could be the indicator to identify the drought resistance of trees, being of the same mind about this conclusion is the study of Nainanayake (2007) [8] on the coconut. According to Percival GC and Noviss K (2008) [10], chlorophyll content in leaf and high chloro- phyll fluorescence enhanced tolerance to prolonged drought, helped the plant recover faster after the drought season. Stability index of chlorophyll also closely associated with grain production of pearl millet cultivars (Panicum miliaceum) under natural drought (Masood Ali, 1986) [5]. Research on drought-resistance in peanuts (Arachis hypogaea L.), Arunyanark, A et al. (2008) [1] confirmed that the stability of chloro- phyll is an indicator of drought tolerance in peanut. In this paper we present the initial results of analysis of the relationship between drought-resistance and chloro- phyll content in leaf tissues of twenty five local upland varieties to provide the basis for the selection of upland rice varieties with high resistance. 2. Content 2.1. Materials and methods ∗ Materials: Twenty-five local upland rice cultivaters were used as research material. Local names, rice accessions and locations collecting samples are shown in Table 1. The twenty five upland rice cultivaters are provided by the Plant Genetic Resources of Vietnam, Vietnam Academy of Agricultural Sciences. 162 Relations between drought-resistance and chlorophyll content... Table 1. List of upland rice cultivaters No Rice Name Location No Rice accession Name Location accession 13 Kn Khau nghe Tuyen Quang 1 Bcc Blao co ca Son La 14 Kp Khau pe Son La 2 Bcs Blao chinh sai Hoa Binh 15 Kpl Khau pe lanh som Son La 3 Bct Blao cong ton Hoa Binh 16 Kt Khau then Bac Kan 4 Bic Bieo chim tri Bac Kan 17 Kx Khau xe Son La 5 Blt Ble to Lai Chau 18 Ln Lua nuong Ha Giang 6 Blx Ble xenh xi Son La 19 Lo Lua oi Hoa Binh 7 Bsn Blao sa ngay Son La 20 Ltn Lua te nuong Ha Giang 8 Gb Giang bau Quang Ninh 21 Md Mo dam Bac Kan 9 Kk Khau ken Cao Bang 22 Mt Mo trang Lao Cai 10 Kld Khau lay deng Cao Bang 23 Nn Nep nng Hoa Binh 11 Klk Khau lay khao Cao Bang 24 Nro Ngo ri o Lai Chau 12 Km Khau mo Son La 25 Ss Soam si Tuyen Quang ∗ Methods: Chlorophyll content was determined by the method of Wintermans, De Mots [6]. Concentrations of chlorophyll a, chlorophyll b and total is calculated by the following formulas: Ca (mg/l) = 12.7.E663 - 2.69.E645 Cb (mg/l) = 22.9.E645 - 4.68.E663 Ca+b (mg/l) = 8.02.E663 + 20.2.E645 Chlorophyll content per one gramme of leaf fresh weight was calculated by the following formula: A = CV p.1000 where A: the chlorophyll content in leaf (mg/g leaf fresh weight) C: concentration of chlorophyll (mg/l) V: volume of pigment extract (ml) p: sample weight (gramme) Bond chlorophyll was determined according to I.G.Shmatco et al. [6]. Water retention capability of leaf tissues was determined according to G.N. Ecmeev [6]. 163 Nguyen Thi Ngoc Lan, Chu Hoang Mau and Nguyen Nhu Khanh 2.2. Results and discussion 2.2.1. Water retention of leaf tissues In the process of growth and development of rice, the seedling stage is the period that the young rice is very vulnerable due to the adverse effects of stress environment. Therefore, we identified the water retention capacity of leaf tissue in rice at the seedling stage based on results monitoring water loss over the periods of one hour, two hours, three hours, four hours, five hours and six hours (Table 2). The less amount of water loss by the same amount of leaf tissue per unit of time, the higher young rice has water retention capacity and vice versa. A little amount of water loss helps plants to have better resistance to drought stress. According to the experimental results, water retention capacity of leaf tissue in all upland rice varieties decreased over test times that was shown by the increase in water loss (Figure 1). The amount of water loss at the same time after one-hour- ranges is between 11.197% and 17.956%, after six hours the amount of water loss from leaf tissues of twenty five upland rice cultivaters has reached the value range from 43.707% to 63.504%. Figure 1. Water retention of leaf tissue 164 Relations between drought-resistance and chlorophyll content... At each monitoring time, the result showed that Gb cultivar had the lowest amount of water loss. This means the leaf tissue of Gb cultivar has the best water retention capacity in comparison with the other upland rice cultivars, so Gb can tolerate dehydration conditions better. In contract, Klk cultivar has the highest values of water loss of leaf tissue in drought stress over time. Basing on this result, it should be concluded that Klk seedlings is the less drought-resistant rice varieties. Table 2. Parameters and statistics on water loss of leaf tissue Time Min Max Average Standard deviation Coefficient of variation (%) 1 hour 11.197 17.956 13.712 1.936 10.149 2 hours 20.585 28.321 23.624 2.613 6.843 3 hours 26.049 36.934 30.574 3.353 5.989 4 hours 31.902 46.861 38.691 4.553 5.515 5 hours 37.268 54.599 45.877 5.196 4.969 6 hours 43.707 63.504 54.362 6.007 4.508 2.2.2. Chlorophyll content in leaves of upland rice varieties Photosynthetic apparatus in leaves are often very sensitive to environmental changes. In drought stress, not only the synthesis of new chlorophyll is interrupted but also the structure of the photosynthetic apparatus is damaged. This leads to changes in the amount of total chlorophyll and bond chlorophyll in leaves, so we analysed chlorophyll content in leaf tissues of twenty five local upland rice cultivars (Table 3). According to the results in Table 3, total chlorophyll content of twenty five upland rice varieties range from 1.496 to 1.962 (mg/g leaf fresh weight) and ranked in order from high to low values of total chlorophyll content to be Gb> Bsn > Md> Ln> Bcc> Kn> Ss> Bcs> Nn> Ltn> Mt> Blt> Km> Nro> Lo> Kk> Bct> Kp> Kt> Bic> Kpl> Blx> Kld> Kx> Klk. The values of bond chlorophyll content in the leaves among twenty-five upland rice varieties are different from the values of total chlorophyll content, but Gb cultivar still has the highest bond chlorophyll content in three groups (chlorophyll a, chlorophyll b, chlorophyll (a+b)) and Klk variety has the lowest. 165 Nguyen Thi Ngoc Lan, Chu Hoang Mau and Nguyen Nhu Khanh Table 3. Total chlorophyll and bond chlorophyll content in leaves Chlorophyll total Chlorophyll bond Rice (mg/g leaf fresh weight) (mg/g leaf fresh weight) accession Chla Chlb Chl (a+b) Chla Chlb Chl (a+b) Bcc 1.386 0.522 1.908 0.648 0.272 0.921 Bcs 1.262 0.575 1.837 0.556 0.254 0.810 Bct 1.125 0.490 1.616 0.496 0.230 0.725 Bic 1.189 0.411 1.600 0.476 0.234 0.710 Blt 1.308 0.487 1.795 0.518 0.222 0.740 Blx 1.152 0.407 1.559 0.465 0.230 0.694 Bsn 1.332 0.626 1.958 0.718 0.272 0.989 Gb 1.408 0.554 1.962 0.671 0.319 0.990 Kk 1.214 0.425 1.639 0.502 0.224 0.726 Kld 1.130 0.425 1.555 0.485 0.177 0.662 Klk 1.100 0.395 1.496 0.408 0.202 0.611 Km 1.258 0.427 1.685 0.531 0.204 0.736 Kn 1.329 0.572 1.901 0.627 0.257 0.883 Kp 1.191 0.422 1.613 0.511 0.207 0.718 Kpl 1.179 0.402 1.581 0.495 0.202 0.697 Kt 1.188 0.422 1.609 0.475 0.236 0.712 Kx 1.132 0.413 1.545 0.427 0.197 0.623 Ln 1.316 0.615 1.931 0.656 0.314 0.970 Lo 1.203 0.461 1.664 0.485 0.241 0.726 Ltn 1.361 0.454 1.815 0.524 0.252 0.776 Md 1.366 0.565 1.931 0.658 0.312 0.970 Mt 1.294 0.509 1.802 0.526 0.244 0.770 Nn 1.239 0.597 1.836 0.571 0.230 0.801 Nro 1.243 0.437 1.680 0.506 0.232 0.738 Ss 1.373 0.474 1.847 0.550 0.262 0.812 2.2.3. Relationship between water retention capacity and chlorophyll content To study the relationship between water retention capacity and chlorophyll content of leaf tissues, we have tabulated the correlation between the average amount of water loss after one hour (%) and total chlorophyll content (chlorophyll a , chloro- phyll b, chlorophyll (a+b)) and bond chlorophyll content (chlorophyll a, chlorophyll b, chlorophyll (a+b)) (mg/g leaf fresh weight) (Table 4). 166 Relations between drought-resistance and chlorophyll content... Table 4. Correlation between water loss and chlorophyll content Indicator Average amount of water loss after one hour (%) Total chlorophyll a -0.788a Total chlorophyll b -0.608a Total chlorophyll (a+b) -0.854a Bond chlorophyll a -0.752a Bond chlorophyll b -0.600a Bond chlorophyll (a + b) -0.764a a: p < 0.001 Correlation analysis results showed that the amount of water loss is inversely proportional to the value of chlorophyll content in leaves at all the indicators. This shows that chlorophyll content is correlative with the average amount of water loss after one hour (%) in leaf tissues or dehydration tolerance in plants. Therefore, it can be considered that indicators of chlorophyll content in leaves is a criterion for evaluating and selecting drought-resistant rice varieties. 3. Conclusion Water retention of leaf tissues of twenty local upland rice varieties was de- termined by the amount of water loss through different times. 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