Hydroponic studies were conducted to investigate the role of iron plaque on transport and distribution of chromium (Cr) by rice seedlings. Microscopical observations indicate that iron plaque developed quickly at the root surface of rice seedlings, but the distribution of iron plaque was more intense near root base and less towards root tip. Results showed that rice seedlings exposed to Cr(III) depicted significantly higher capacity for Cr accumulation in plant tissues than Cr(VI) in the presence of iron plaque. However, transport of Cr within plant cells was more evident in Cr(VI) treatment with iron plaque than Cr(III) treatment. Results also showed that there are significant impact on transport of K, Mn and Zn in rice seedlings treated with Cr(VI) in the presence of iron plaque, while significant effect on transport of Mn and Zn were observed in Cr(III)-treated rice seedlings. Results from detached root test provide additional evidence to confirm the presence of iron plaque, that had different impact on Cr uptake when Cr(VI) or Cr(III) was supplied.
Authors:X.R. Yu, L. Zhou, J. Zhang, H. Yu, D.R. Gao, B.Q. Zhang, F. Xiong, Y.J. Gu, and Z. Wang
This study was conducted to compare structural development and biochemical accumulation of waxy and non-waxy wheat (NW) caryopses. The caryopses’ microstructure of the waxy wheat (WW) and NW cultivars at different developmental stages were observed under light, fluorescence, and scanning electron microscope. The results were as follows: Compared with NW,WWhad a shorter maturation duration, which was reflected in several following characteristics. Programmed cell death of the pericarp began earlier, and the chlorophyll-containing layer in the pericarp was smaller. Vacuoles in chalazal cells accumulated more tannins at different developmental stages. Starch granules and protein bodies in the endosperm showed a higher accumulation level in developing caryopses, and aleurone cells were larger in size with larger numbers of aleurone grains. An analysis of the element content indicated that the mineral elements Mg, P, K, and Ca exhibited a higher content, while the heavy elements Cr, Cd, and Pb exhibited a lower content in the aleurone layer.
Authors:H. Yu, Y. Yang, X.Y. Chen, G.X. Lin, J.Y. Sheng, J.Y. Nie, Q.J. Wang, E.J. Zhang, X.R. Yu, Z. Wang, and F. Xiong
The waxy wheat shows special starch quality due to high amylopectin content. However, little information is available concerning the development and degradation of amyloplast from waxy wheat endosperm. To address this problem, waxy wheat variety, Yangnuo 1, and a non-waxy wheat variety, Yangmai 13, were chosen to investigate the development and degradation of endosperm amyloplast during wheat caryopsis development and germination stage respectively using histochemical staining and light microscopy. Changes of morphology, the soluble sugar and total starch content were indistinguishable in the process of caryopsis development of two wheat varieties. The developing endosperm of non-waxy was stained blue-black by I2-KI while the endosperm of waxy wheat was stained reddish-brown, but the pericarp of waxy and non-waxy wheat was stained blue-black. In contrast to nonwaxy wheat, endosperm amyloplast of waxy wheat had better development status and higher proportion of small amyloplast. During seed germination many small dissolution pores appeared on the surface of endosperm amyloplast and the pores became bigger and deeper until amyloplast disintegrated. The rate of degradation of waxy wheat endosperm amyloplast was faster than non-waxy wheat. Our results may also be helpful to the use of waxy starch in food and nonfood industry.
Authors:Y.P. Jing, D.T. Liu, X.R. Yu, F. Xiong, D.L. Li, Y.K. Zheng, Y.F. Hao, Y.J. Gu, and Z. Wang
The objective of the present study was to understand the developmental regularity of wheat endosperm cells at different Days After Pollination (DAP) using microscopic and histochemical methods. Resin semi-thin sections of the endosperm and the enzymatically dissociated Starchy Endosperm Cells (SECs) were observed under a light microscope. The results showed that: (1) SECs were irregular-shaped and had two types of starch granules: large oval-shaped A-type starch granules and small spherical B-type starch granules. (2) The growth shape of SECs was referred to as S-curve and the fastest cell growth period was at 16–24 DAP. (3) The largest increase and growth of A-type starch granules were mainly at 4–16 DAP. B-type starch granules increased rapidly after 16 DAP and made up over 90% of the total starch granules in SEC during the late stage of endosperm development. (4) The nuclei of SEC deformed and degenerated during the middle and late stages of endosperm development and eventually disappeared. However, starch granules still increased and grew after the cell nuclei had degenerated. The investigations showed the development regularity of starch endosperm cells and starch granules, thereby improving the understanding of wheat endosperm development.