The effect of low pH on physiological characters in vegetatif phase of Kalimantan local swamp rice (Oryza sativa L.)

Indonesia is a country with high rice consumption and also potential to develop local rice plants with adaptation to tidal swamp. This study aimed to analyze physiological characters of local Kalimantan swamp rice cultivars in low pH condition. To achieve this purpose, plants were grown hydroponically with two pH variation, 4 (low pH) and 6.8 (normal). This study used 6 cultivars namely ‘Amas’, ‘Pandan Ungu’, ‘Kambang’, ‘Sikin Merah’, ‘Argo Pawan’, ‘Suatek Merah’, and 2 comparative cultivars ‘Inpara 5’ and ‘Ciherang’. Growth characters were observed by measuring plant height, leaf length and width, and leaf number up to 21 DAT (Day After Treatment). Physiological characters observed including chlorophyll, carotenoid and proline content of leaves as measured on 21 DAT. Under low pH condition, the physiological characters of some swamp rice cultivars were better than that under pH 6.8. This can be seen from plant performance showing higher plant, longer and wider leaves, and more of leaf number in ‘Amas’, ‘Pandan Ungu’, and ‘Kambang’. In addition, at pH 4 treatment, there was a higher in total chlorophyll content in ‘Pandan Ungu’ and ‘Kambang’ and higher carotenoid content in ‘Kambang’. Meanwhile, proline levels of swamp rice cultivars increased at pH 6.8 indicated that these cultivars are more tolerant to low pH. Based on the results it can be concluded that pH 4 treatment provides high stability in growth (plant height, leaf length, and width, leaf number), chlorophyll, carotenoid and proline content in ‘Amas’, ‘Pandan Ungu’, and ‘Kambang’.