Gametophyte development, antioxidant properties and response to salinity of Brassica rapa L. var. parachinensis

Brassica vegetables has been studied extensively due to high nutritional and medicinal values, as it is naturally low in fat, cholesterol, calories and sodium but rich in potassium, fiber, folic acid, and vitamins A, C, and K. This study was conducted to discover gametophyte development of B. rapa var. parachinensis, to compare antioxidant properties between leaves and seed of B. rapa var. parachinensis and among B. rapa var. parachinensis, B. oleracea cv. alboglabra and B. rapa cv. chinensis. The effects of individual salt that is NaCl, KCl and MgCl2 on germination and seedling growth of B. rapa var. parachinensis were studies. Seeds (15 seeds) of B. rapa var. parachinensis plants were grown in a pot containing a mixture of top soil and river soil with ratio 3:1 at University Agricultural Park, Universiti Putra Malaysia (UPM) from July - December 2012. The inflorescences of B. rapa var. parachinensis in different stages which are from youngest buds to mature flowers were tagged, collected and fixed in FAA 70 (20% formalin, 10% acetic acid, 70% ethanol, v/v) and followed by histological works to discovered male and female gametophyte development. Gametophyte development of B. rapa var. parachinensis found similar with other angiosperms and Brassica. New embryological characteristics had been explored and not reported yet in any Brassicaceae which are the reduced type of anther wall development and the ovule type is Hemitropous. Pollen grain is rounded to ovate, triporate and tricellular. The female gametophyte is monosporic with polygonum type pattern. The composition and antioxidant capacity between leaves and seeds of B. rapa var. parachinensis and of three Brassica vegetables which are B. rapa var. parachinensis, B. oleracea cv. alboglabra and B. rapa cv. chinensis was studied. Seeds of B. rapa var. parachinensis, B. oleracea cv alboglabra and B. rapa cv chinensis were grown in the mixture soil with ratio 3 top soil and 1 river soil at Taman Pertanian Universiti, UPM from January – August 2014. Total chlorophylls, caretonoid, phenolics, flavonoids and ascorbic acid were measured spectrophotometrically. DPPH radical scavenging activity and reducing power assay was conducted to measure the antioxidative activity. Leaves and seeds of B. rapa var. parachinensis have significantly distinct antioxidative components (t-test, p<0.05) and the extract of seed has significantly higher capacity as scavenger of DPPH radical and reducing power than leaves (t-test, p<0.05). The antioxidative profiling of B. rapa var. parachinensis, B. oleracea cv. alboglabra and B. rapa cv. chinensis are significantly different (ANOVA, p<0.05). B. rapa var. parachinensis leaves contains significantly higher of chlorophyll (49.9 mg/0.1 g ± 2.3), carotenoid (31.1 mg/0.1 g ± 1.3) and flavonoid (0.03 mg/0.1 g ± 0.0005) than B. oleracea cv. alboglabra and B. rapa cv. chinensis. On the other hand, B. rapa cv. chinensis leaves contain higher ascorbic acid than B. rapa var. parachinensis and B. oleracea cv. alboglabra. The effects of individual salts, NaCl, KCl and MgCl2 were studied on germination and early seedling growth of B. rapa var. parachinensis. Four concentrations 50, 100, 150 and 200 mM were used for each salinity. The number of germinated seeds was recorded daily for 9 days. Hypocotyl and radical length and biomass of each seedling was measured at day 9. Germination percentage (% GP), salt tolerant and seed vigor were measured. Brassica rapa var. parachinensis seed had more viability with NaCl and KCl, but sensitive to MgCl2. The seed vigor and tolerance are significantly (p<0.05) higher in KCl than NaCl in which the highest tolerance in 100 mM KCl. The patterns of hypocotyl and radical length found different in which NaCl retard the hypocotyls length but increased the radical length and biomass. On the other hand, KCl at any concentration increased the seed vigor, the tolerance, the length of both hypocotyls, radical and biomass. In conclusion, gametophyte development in B. rapa var. parachinensis was found similar to other flowering plants. Seeds of B. rapa var. parachinensis rich on antioxidant compared with leaves. The present findings also discovered that B. rapa var. parachinensis is a NaCl- tolerant and KCl- tolerant cultivars.

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