Authors:Z. Gyenes-Hegyi, I. Pók, L. Kizmus, and et al.
The plant height and the height of the main ear were studied over two years in twelve single cross maize hybrids sown at three different plant densities (45, 65 and 85 thousand plants/ha) at five locations in Hungary (Keszthely, Gönc, Gyöngyös, Sopronhorpács, Martonvásár). The results revealed that plant height and the height of the main ear are important variety traits and are in close correlation with each other. It was found that the hybrids grew the tallest when the genetic distance between the parental components was greatest (Mv 4, Mv 5). The height of the main ear was also the greatest in these hybrids, and the degree of heterosis was highest (193% for plant height, 194% for the height of the main ear). The shortest hybrids were those developed between related lines (Mv 7, Mv 11). In this case the heterosis effect was the lowest for both plant height (128%) and the height of the main ear (144%). The ratio of the height of the main ear to the plant height was stable, showing little variation between the hybrids (37–44%). As maize is of tropical origin it grows best in a humid, warm, sunny climate. Among the locations tested, the Keszthely site gave the best approximation to these conditions, and it was here that the maize grew tallest. The dry, warm weather in Gyöngyös stunted the development of the plants, which were the shortest at this location. Plant density had an influence on the plant size. The plants were shortest when sown at a plant density of 45,000 plants/ha, and the main ears were situated the lowest in this case. At all the locations the plant and main ear height rose when the plant density was increased to 65,000 plants/ha. At two sites (Gönc and Sopronhorpács) the plants attained their maximum height at the greatest plant density (85,000 plants/ha). In Keszthely there was no significant difference between these two characters at plant densities of 65 and 85 thousand plants/ha, while in Gyöngyös and Martonvásár the greatest plant density led to a decrease in the plant and main ear height. The year had a considerable effect on the characters tested.
Authors:N. Zhang, R.Q. Pan, J.J. Liu, X.L. Zhang, Q.N. Su, F. Cui, C.H. Zhao, L.Q. Song, J. Ji, and J.M. Li
Plants with deficiency in Gibberellins (GAs) biosynthesis pathway are sensitive to exogenous GA3, while those with deficiency in GAs signaling pathway are insensitive to exogenous GA3. Thus, exogenous GA3 test is often used to verify whether the reduced height (Rht) gene is involved in GAs biosynthesis or signaling pathway. In the present study, we identified the genetic factors responsive to exogenous GA3 at the seedling stage of common wheat and analyzed the response of the plant height related quantitative trait loci (QTL) to GA3 to understand the GAs pathways the Rht participated in. Recombinant inbred lines derived from a cross between KN9204 and J411 with different response to exogenous GA3 were used to screen QTL for the sensitivity of coleoptile length (SCL) and the sensitivity of seedling plant height (SSPH) to exogenous GA3. Two additive QTL and two pairs of epistatic QTL for SCL were identified, meanwhile, two additive QTL and three pairs of epistatic QTL for SSPH were detected. For the adult plant height (PH) investigated in two environments, six additive QTL were identified. Three QTL qScl-4B, qSsph-4B and qPh-4B were mapped in one cluster near the functional marker Rht-B1b. When PH were conditional on SSPH, the absolute additive effect value of qPh-4B and qPh-6B were reduced, suggesting that the Rhts in both two QTL were insensitive to exogenous GA3, while the additive effect values of qPh-2B, qPh-3A, qPh-3D and qPh-5A were not significantly changed, indicating that the Rhts in these QTL were sensitive to exogenous GA3, or they were not expressed at the seedling stage.
Authors:L. Wang, F. Cui, A. Ding, J. Li, J. Wang, C. Zhao, X. Li, D. Feng, and H. Wang
A recombinant inbred line (RIL) population with 302 lines derived from a cross of Weimai 8 × Luohan 2 was used to identify the quantitative trait loci (QTL) for plant height (PH) in wheat (Triticum aestivum L.). Possible genetic relationships between PH and PH components (PHC), including spike length (SL) and internode length from the first to the fourth node counted from the top, abbreviated as FIITL, SITL, TITL and FOITL, respectively, were evaluated at the QTL level. A QTL for PH was mapped using data on PH and on PH conditioned by PHC using the IciMapping V3.0 software. Conditional QTL mapping proved that, at the QTL level, SL contributed the least to PH, followed by FIITL and FOITL, while TITL had the strongest influence on PH, followed by SITL. These results indicate that the conditional QTL mapping method can be used to evaluate possible genetic relationships between PH and PHC, and that it can efficiently and precisely reveal counteracting QTL, which will enhance our understanding of the genetic basis of PH in wheat.
Hypothesising that competition is a major ecological factor that filters plants on the basis of traits, we tested whether competition intensity and importance were better explained by the functional structure of communities than by standing biomass. We re-analysed data of three experiments in which one to four species of phytometers have been transplanted with or without vegetation in communities displaying a range of standing biomass. Changes in performance of phytometers among communities were used to assess competition intensity and importance. The functional structure of each community was characterized by the mean and functional divergence of plant height, a trait significantly related to resource depletion by competition. Relationships between competition components and standing biomass or functional structure of communities were calculated for each experiment. Competition importance was explained more significantly by the mean of plant height than by the standing biomass of communities. When the range of functional diversity was large enough, the importance of competition was high in communities with low functional diversity because of similarity in functioning among highly competitive plants, and low in more diverse communities. Competition intensity generally showed lower or no relationship with standing biomass or functional structure of communities. These results confirm the dependence of competition on functional structure of communities.
Authors:W. Qi, X. Zhou, M. Ma, J. M. H. Knops, W. Li, and G. Du
Despite a long history of alpine meadows studies, uncertainty remains about the importance of environmental factors in structuring their assembly. We examined the functional and phylogenetic structure of 170 alpine Tibetan meadow communities in relation to elevation, soil moisture and shade. Functional community structure was estimated with both communityweighted mean (CWM) trait values for specific leaf area (SLA), plant height and seed mass and functional diversity (Rao’s quadratic index) for their traits individually and in combination (multivariate functional diversity). We found that shade induced by woody plants significantly increased the phylogenetic diversity and functional diversity of SLA of co-occurring species, suggesting that woody plants behave as “ecosystem engineers” creating a different environment that allows the existence of shade tolerant species and thereby facilitates the coexistence of plant species with different light resource acquisition strategies. We also found evidence for a clear decrease in phylogenetic diversity, CWM and functional diversity related to plant height in the two extreme, both the dry and wet, soil moisture conditions. This indicates that both drought and excess moisture may act as environmental filters selecting species with close phylogenetic relationships and similar height. Moreover, we detected significant decreases in both CWM and functional diversity for seed mass along elevational gradients, suggesting that low net primary productivity (NPP) limits seed size. Finally, because of different individual trait responses to environmental factors, the multivariate functional diversity did not change across environmental gradients. This lack of multivariate response supports the hypothesis that multiple processes, such as environmental filtering, competition and facilitation, may operate simultaneously and exert opposing effects on community assembly along different niche (e.g., water use, light acquisition) axes, resulting in no overall functional community structure change. This contrast between individual and multivariate trait patterns highlights the importance of examining individual traits linked with different ecological processes to better understand the mechanisms of community assembly.
The identification of functional traits critical to plant responses to the environment promotes our understanding of assembly of communities which relies on environmental filtering. However, the recent trait-community approaches mostly ignore the influence of plant-plant interactions by mainly focusing on traits related to abiotic filtering processes. The conceptual framework we propose aims to clarify how the functional diversity of communities depends on the filtering effect of competition on relevant traits. We define two types of competition-related traits:
competitive effect traits
reflect the changes in local resource levels due to plant activity while
competitive response traits
are related to plant response to these resource depletions. We then suggest that the contribution of both types of competition-related traits to functional diversity depends on the importance of competition, previously defined as the effect of competition on plant fitness relative to that of other environmental factors. Therefore, the divergence of functional diversity is predicted to be maximized at intermediate levels of competition in relation to the coexistence of species with different strategies characterized by highly contrasted values of competition-related traits.