Root distribution of winter wheat cultivars as affected by drought
Abstract
Drought stress is one of the main environmental factors limiting crop yields. Choice of drought-resistant cultivars may minimise yield-losses under water-limited conditions. The development of a deeper root system contributes to increased drought resistance. Based on this information, the genotypic variation in root system distribution in winter wheat was examined in a field experiment either under natural rainfed conditions or with an induced water deficit. The distribution of roots was quantified at the wax-ripe stage (EC 83). Root length densities were highest in the top 20 cm. Drought-stressed plants tended to produce less overall root length, and cultivars differed significantly in overall root lengths produced. Cultivars seemed to differ in their reaction to drought stress, but the difference was not significant. In conclusion, data from additional growing seasons will be necessary to confirm variation in root distribution between cultivars in their response to drought-stress.
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- Newly installed plants and poorly established plants may be especially susceptible to drought stress because of the limited root system or the large mass of stems and leaves in comparison to roots [76,77]. Soil mechanical impedance against root growth and development is caused mainly by natural processes and by the use of heavy machinery for soil cultivation [78,79]. The root system of an individual plant consists of several component roots of different nature.
- The varieties differed substantially for root mass and V3 in both the annual and perennial class produced the highest root mass in uppermost soil (0-30 cm). These results are in agreement with findings of studies conducted by Schweiger et al. (2009). It is suggested that wheat spread its major portion in top soil layers to increase the surface area for efficient use of nutrient and soil water.
[Show abstract] [Hide abstract] ABSTRACT: The agronomic and root growth performance of three perennial wheat varieties i.e CS + 4J (21 + 1), {(CIMMYT 4J Addition (21 + 1)} and (CS/Th. bessarabicum (complete amphiploid) 21+7) and three annual, including Inqulaib-91, B. Yellow and Claire were compared in Randomised Complete Block Design. The results revealed that root elongation of both groups ceased after 7 th week. The tested genotypes maintained quantitative proportionality with respect to root and shoot development. Inter varietals within both groups could not produced statistically different values for plant height. The varieties lies in perennial group gave significantly encouraging results except plant height and dry weight over annuals for above as well as below ground plant parts but we can expect the limited grains production from perennials. Among annuals, the V3 and from perennial no single variety proved to be superior for all desirable traits. Both the groups distributed most of their root mass in upper 30 cm soil layer and only a minor portion of roots was extended to 120 cm depth. Even though, the varieties from perennial group performed well for plant biomass but it is never recommended to replace annuals with perennials for grains. However, their use as forage, soil and environment conservation crop is more reliable.- Since higher relative water content and higher leaf area index or seed yield can be related to deep roots (Hirayama et al., 2006), it seems that with selection of those genotypes, which have the highest first component, we can select deep root and drought tolerant genotypes. A Root characteristic is one of the most important traits to find drought tolerant genotypes however it is hard to study or measurement (Schweiger et al., 2009). Selection based on root characteristic, helps to selection of the best genotypes which have high genetic potential against drought stress.
[Show abstract] [Hide abstract] ABSTRACT: ABSTRACT: Drought stress is one of the major limitations to plant productivity across the world. Identifying suitable screening tools and also quantifiable traits would facilitate the crop improvement process for drought tolerance. In the present study, relative water content, leaf area index, stomata density and stomata length were studied as most important physiological parameters at the grain filling stage of fifteen spring safflower genotypes grown under normal and drought stress conditions in 2007 growing season. The experiment was conducted in Zanjan University, Zanjan, Iran based on randomized complete block design, arranged in split plot with three replications. The results indicated that exposure of plants to drought stress led to significant decrease in relative water content, leaf area index and stomata length and noticeable increase in stomata density. Decrease in above mentioned traits was parallel with yield loss in sensitive genotypes. The results of principal component analysis showed that the first component with more than 68% of total variation is able to separate high yield genotypes from other genotypes. According to obtained results, it seems that Dincer, Kino-74, PI-537598, PI-250537 and Gila genotypes are more suitable genotypes for drought stressed regions.- [Show abstract] [Hide abstract] ABSTRACT: Background and aims In Mediterranean-type environments, effective capture of intermittent rainfall is important for crop drought tolerance. Two wheat genotypes RAC875 and Kukri differing in drought tolerance vary in several shoot traits and grain yield. Little is known about root traits contributing to drought tolerance. This study examined dynamic root responses to cyclic drought in these two contrasting genotypes. Methods A pot experiment was conducted by exposing plants to moderate drought before heading, and then rewatering. Root responses were determined for coarse and fine root length density (RLD), root DNA concentration (RDC), nodal root properties, and metaxylem and protoxylem features of both primary and nodal roots in proximal and distal regions. Results Moderate drought reduced fine RLD and inhibited new nodal root growth. Rewatering promoted new nodal root growth. Drought-tolerant RAC875 showed higher relative growth of newly emerged nodal roots than drought-intolerant Kukri after rewatering. RAC875 also had smaller diameter and total area of metaxylem vessels in nodal roots than Kukri, but higher number of metaxylem vessels and RDC independent of water regime. Conclusions Multiple root traits identified could confer RAC875 advantage in drought tolerance under Mediterranean-type environments through conservative use of water and reduced risk of embolism, rapid responses to rainfall and root survival.
- [Show abstract] [Hide abstract] ABSTRACT: Studies after the function of root traits and the genetic variation in these traits are often conducted under controlled conditions using individual potted plants. Little is known about root growth under field conditions and how root traits are affected by agronomic practices in particular sowing density. We hypothesized that with increasing sowing density, root length density (root length per soil volume, cm cm-3) increases in the top soil as well as specific root length (root length per root dry weight, cm g-1) due to greater investment in fine roots. Therefore, we studied two spring barley cultivars at ten different sowing densities (24-340 seeds m-2) in two consecutive years in a clay loam field in Germany and established sowing density dose response curves for several root and shoot traits. We took soil cores for measuring roots up to a depth of 60 cm in and between plant rows (inter-row distance 21 cm). Root length density increased with increasing sowing density and was greatest in the plant row in the top soil (0-10 cm). Greater sowing density increased specific root length partly through greater production of fine roots in the top soil. Rooting depth of the major root axes (root diameter class 0.4-1.0 mm) was not affected. Root mass fraction decreased, while stem mass fraction increased with sowing density and over time. Leaf mass fraction was constant over sowing density but greater leaf area was realized through increased specific leaf area. Considering fertilization, we assume that light competition caused plants to grow more shoot mass at the cost of investment into roots, which is partly compensated by increased SRL and increased shallow rooting. Increased biomass per area with greater densities suggest that density increases the efficiency of the cropping system, however, declines in harvest index at densities over 230 plants m-2 suggest that this efficiency did not translate into greater yield. We conclude that plant density is a modifier of root architecture and that root traits and their utility in breeding for greater productivity have to be understood in the context of high planting densities.
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