Nutrients, ultrastructures, and Cd subcellular localization in the cottonseeds of three upland cotton cultivars under Cd stress

Abstract

A pot experiment was performed to study the Cd-induced alterations in seed quality at maturity in two transgenic upland cotton cultivars, ZD-90 and SGK3, and the upland cotton standard line, TM-1. The results shown that Cd content in cotton kernels increased linearly with the elevation of Cd stress levels. SGK3 accumulated more Cd than others. Protein content in the kernels was increased under Cd stress generally, but those at 600 µM Cd level were lower than that under 400 µM Cd level. The changes in oil content were inversed to that of protein content. Significant ultra-structural changes in cottonseeds were induced by Cd stress, especially at higher Cd levels, which were more obvious in TM-1, followed by ZD-90 and SGK3. Plasmolytic shrinkage, disintegration of nucleus, cell wall thickening, and eventual cell collapse and disintegration were observed in the cells of cottonseeds under Cd stress. Transmission electron microscope (TEM) observation and energy dispersive X-ray analysis (EDAX) confirmed that Cd existed in the form of rings and crystals as well as electron dense granules, occurred in the intercellular space, the cytoplasm, and the cell wall. SGK3 was a tolerance cultivar to Cd stress with greater Cd accumulation and sequestration in cottonseeds.

Selection for Cd Pollution-Safe Cultivars of Chinese Kale (Brassica alboglabra L. H. Bailey) and Biochemical Mechanisms of the Cultivar-Dependent Cd Accumulation Involving in Cd Subcellular Distribution

“…Previous researchers have demonstrated that the plant tissues have a barrier for Cd translocation, which can inhibit the transfer of Cd from roots to shoots. This process is mainly regulated by the loading capacity of xylem in root, the content of long-distance carriers, such as PCs, and the compartmentalization of root cell wall and vacuole. , Although the BF of Cd decided that Chinese kale is a Cd accumulative species, the differences between low- and high-Cd cultivars in TFs of Cd were larger than those of BFs. It is thus suggested that the cultivar dependent Cd accumulation of Chinese kale mainly relied on cultivar difference of Cd translocation from roots to shoots, which can be well explained by the differences of Cd subcellular distributions between the low- and high-Cd cultivars.…”

“…It was reported that more than 70% Cd intake by humans originate from vegetables consumption . Therefore, it is urgent to reduce the potential health risks by minimizing Cd accumulation in edible parts of vegetable crops. , …”

“…4 Therefore, it is urgent to reduce the potential health risks by minimizing Cd accumulation in edible parts of vegetable crops. 5,6 Although there are various technologies to remediate soil Cd contamination, it is still difficult to put them into practice in farmland due to many limited conditions such as long-term fallow, high cost, and potential risk of secondary pollution. 7,8 In recent years, proper cultivar selection has been proposed as a practical eco-friendly approach to restrict Cd uptake and accumulation in crops and finally limits the movement of Cd into the human diet.…”

Insights into the Roles of Melatonin in Alleviating Heavy Metal Toxicity in Crop Plants

“…Cd, Pb, Cr, and other metals are nonessential elements for plant growth and can compete with certain essential metal ions in crops, leading to a lack of relevant essential metal ions, causing nutrient deficiency symptoms, and even inhibiting plant growth or causing death [36]. Cd stress inhibited the elongation and growth of the aboveground and underground parts of rice, wheat, cotton, potato and other crops, and the biomass was significantly lower than normal [37][38][39][40]. Pb stress caused a decrease in plant height and biomass of sweet sorghum and corn [41], and a significant decrease in root biomass and the number of lateral roots [42].…”

“…The inhibitory effect of heavy metals on chlorophyll synthesis and photosynthesis is positively correlated with the extension of the treatment time and the increase in the treatment concentration in crop plants. Studies have shown that Cd caused a significant decrease in the contents of chlorophyll and carotenoids in rice, potato and rape leaves [38,40,52]; additionally, the chlorophyll fluorescence parameters Fv/Fm, ΦPSII and qP in wheat and tomato leaves were significantly decreased, and the photosynthetic system was significantly damaged [53,54], which affected the activity of the large subunit of the key enzyme rubisco and the D1 subunit of the active center in PSI, which hindered electron transfer and reduced CO 2 assimilation efficiency [55,56]. The main reason may be that the activity of chlorophyll lipid reductase was inhibited, the synthesis of amino-γ-levulinic acid was hindered, and the activity of the electron transport chain and PSII was inhibited by Hg 2+ [57].…”