Differences of celery cultivars in cadmium absorption and accumulation

Objectives  Crop cultivars are different in Cd absorption and up translocation. Studying the differences and the suitable index will support the selection of suitable cultivars, though which to minimize the Cd content and provide safe crop productions.

Methods  Ten celery cultivars were chosen as materials for a hydroponic culture experiment with substrates of vermiculite. The 1/2 South China Agricultural University leafy nutrient solution was used as a control, and treatment solution containing 15 mg/L of cadmium chloride (CdCl₂) were prepared at the base of control solution. 0.2 L of solution was watered every 3 days for each pot during 45 days’ growth of celeries, with a total input of Cd 45 mg/pot. The growth index and Cd content in roots, petioles and leaves of celeries were determined; the relative growth yield (RGY) and translocation factor (TF) was calculated, and celeries with different Cd-accumulation levels could be identified. The high- and low-Cd accumulation cultivars were selected and grown in plug trays. The seedlings were watered with the nutrient solution until 14 days, then watered with Cd-containing solution as before. After 21 days’ treatment, the Cd²⁺ flow rate in root meristem, elongation zone and root hair zone was determined using Non-invasive Micro-test Technology (NMT).

Results  The growth and Cd accumulation in shoots and roots of celeries were significantly different under the Cd stress. The for cultivar ‘Sushengsiji xiqinwang’, ‘Wentula xiqin’, ‘Siji xiaoxiangqin’, ‘Shixin xiangqin’ and ‘Xuebai qincai’, their root growth were significantly reduced but their shoots were not by Cd stress, and the shoot growth of ‘Siji xiao xiangqin’ was even promoted; For cultivar ‘Zhongdujinhuang qincai’, ‘Hongqin’ and ‘Baoqin’, in contrast, their shoot growth were significantly reduced but their roots were not by Cd stress; While for cultivar ‘Majiagou qincai’ and ‘Susheng xiangqin’, both the root and shoot growth significantly reduced by Cd stress. The Cd concentrations in leaf stalks, the edible organ, were higher in ‘Zhongdujinhuang qincai’ and ‘Xuebai qincai’, and those were lower in ‘Susheng xiangqin’ and ‘Shixin qincai’. The higher Cd concentration in leaf stalks represented higher capacity of Cd transportation. The Cd²⁺ flux rate in root hair zone of ‘Zhongdujinhuang qincai’ was greater than that of ‘Susheng xiangqin’.

Conclusions  There are significant differences in growth, Cd absorption, transportation and accumulation among celery cultivars under Cd stress. ‘Sijixiao xiangqin’, ‘Sushengsijixi qinwang’, ‘Wentula qincai’, ‘Shixin xiangqin’ and ‘Xuebai qincai’ are tolerance cultivars, and ‘Zhongdujinhuang qincai’, ‘Hongqini’, ‘Baoqin’, ‘Majiagou qincai’ and ‘Susheng xiangqini’ are sensitive cultivars to Cd stress. ‘Xuebai qincai’ and ‘Zhongdujinhuang qincai’ are high Cd accumulation cultivars, where as ‘Shixin xiangqin’ and ‘Susheng xiangqin’ are low Cd accumulation ones. ‘Shixinxiangqin’ shows low Cd accumulation and high growth. Cultivars with high Cd concentration in shoots have strong capacities of Cd absorption in roots and transportation from roots to shoots. The Cd²⁺ flux rate in roots could be used to rapid screen low Cd transport and accumulation celery cultivars.