Developmental Changes in Composition and Morphology of Cuticular Waxes on Leaves and Spikes of Glossy and Glaucous Wheat (Triticum aestivum L.)

Abstract

The glossy varieties (A14 and Jing 2001) and glaucous varieties (Fanmai 5 and Shanken 99) of wheat (Triticum aestivum L.) were selected for evaluation of developmental changes in the composition and morphology of cuticular waxes on leaves and spikes. The results provide us with two different wax development patterns between leaf and spike. The general accumulation trend of the total wax load on leaf and spike surfaces is first to increase and then decrease during the development growth period, but these changes were caused by different compound classes between leaf and spike. Developmental changes of leaf waxes were mainly the result of variations in composition of alcohols and alkanes. In addition, diketones were the third important contributor to the leaf wax changes in the glaucous varieties. Alkanes and diketones were the two major compound classes that caused the developmental changes of spike waxes. For leaf waxes, β- and OH-β-diketones were first detected in flag leaves from 200-day-old plants, and the amounts of β- and OH-β-diketones were significantly higher in glaucous varieties compared with glossy varieties. In spike waxes, β-diketone existed in all varieties, but OH-β-diketone was detectable only in the glaucous varieties. Unexpectedly, the glaucous variety Fanmai 5 yielded large amounts of OH-β-diketone. There was a significant shift in the chain length distribution of alkanes between early stage leaf and flag leaf. Unlike C28 alcohol being the dominant chain length in leaf waxes, the dominant alcohol chain length of spikes was C24 or C26 depending on varieties. Epicuticular wax crystals on wheat leaf and glume were comprised of platelets and tubules, and the crystal morphology changed constantly throughout plant growth, especially the abaxial leaf crystals. Moreover, our results suggested that platelets and tubules on glume surfaces could be formed rapidly within a few days.

Developmental and Genotypic Variation in Leaf Wax Content and Composition, and in Expression of Wax Biosynthetic Genes in Brassica oleracea var. capitata

“…The density and size of wax crystals were greater in high-wax lines than in low-wax lines ( Figure 2 ). Consistent with our results in cabbage, bloomed (waxy) leaves of sorghum and wheat have dense cuticular wax crystals, whereas bloomless (non-waxy) leaves have fewer wax crystals (Tarumoto, 2005; Wang et al, 2015). …”

“…We found six chemical compounds in the cabbage waxes: alkanes, primary alcohols, aldehydes, secondary alcohols, ketols and ketones, but fatty acid was not present (Supplementary Table S2). In contrast to cabbage, low-wax broccoli contained 13.5% and high-wax broccoli contained 15.3% fatty acids (Lee et al, 2015), leaves and stems of wild-type Arabidopsis contained 8.36 and 1.37% (Lu et al, 2012), and leaves of wheat contained 0.5–11.0% fatty acids (Wang et al, 2015). In the present study, we observed dominant alkane chain lengths of C 27 , C 29 , and C 31 , similar to leaves of broccoli (Lee et al, 2015) and stems, leaves and siliques of Arabidopsis (Lee et al, 2009a); by contrast, C 30 alkane appears to be a unique component in cabbage compared to broccoli ( Figure 3 ; Lee et al, 2015).…”

Long noncoding miRNA gene represses wheat β-diketone waxes

“…Grasses in the Triticeae tribe, subfamily Pooideae, which include the cultivated species barley (Hordeum vulgare; 2n = 2x = 14), rye (Secale cereale, 2n = 2x = 14), durum wheat (Triticum durum; 2n = 4x = 28, AABB), and bread wheat (Triticum aestivum; 2n = 6x = 42, AABBDD), have two predominant pathways for wax production: (i) an alcohol-and alkane-rich wax pathway and (ii) a pathway leading to β-diketones and derivatives including hydroxy-β-diketones (2). The alcohol and alkane waxes are prevalent in earlier development and on leaves, whereas β-diketones dominate during the reproductive phase, particularly on leaf sheaths and flower heads (3,4). β-Diketone wax is predominantly hentriacontane-14, 16-dione, which consists of a 31-carbon chain with carbonyl groups at C 14 and C 16 .…”

Evaluating Leaf Wax and Bulk Leaf Carbon Isotope Surrogates for Water Use Efficiency and Grain Yield in Winter Wheat

“…Fuller and TAM 401 both have Jagger as a parent. In contrast, leaf wax n-alkanes have a long-carbon-chain aliphatic structure, and they are the first or second most abundant component in the leaf wax of many species ( Jetter and Schäffer, 2001;Wang et al, 2015). TAM 112 and Duster are the most drought-tolerant cultivars.…”

“…Fannin and TAM 305 also share common parents (Ibrahim et al, 2015). n-Alkanes are not decomposed on the leaf surface after synthesis and harvest (Wang et al, 2015;Gamarra and Kahmen, 2017), which suggests potential for a convenient surrogate for assessing WUE l . Fannin and WB Cedar generally preform below the average in the High Plains due to the low winter temperature.…”