Primary Root and Mesocotyl Elongation in Maize Seedlings: Two Organs with Antagonistic Growth below the Soil Surface

Maize illustrates one of the most complex cases of embryogenesis in higher plants that results in the development of early embryo with distinctive organs such as the mesocotyl, seminal and primary roots, coleoptile, and plumule. After seed germination, the elongation of root and mesocotyl follows opposite directions in response to specific tropisms (positive and negative gravitropism and hydrotropism). Tropisms represent the differential growth of an organ directed toward several stimuli. Although the life cycle of roots and mesocotyl takes place in darkness, their growth and functions are controlled by different mechanisms. Roots ramify through the soil following the direction of the gravity vector, spreading their tips into new territories looking for water; when water availability is low, the root hydrotropic response is triggered toward the zone with higher moisture. Nonetheless, there is a high range of hydrotropic curvatures (angles) in maize. The processes that control root hydrotropism and mesocotyl elongation remain unclear; however, they are influenced by genetic and environmental cues to guide their growth for optimizing early seedling vigor. Roots and mesocotyls are crucial for the establishment, growth, and development of the plant since both help to forage water in the soil. Mesocotyl elongation is associated with an ancient agriculture practice known as deep planting. This tradition takes advantage of residual soil humidity and continues to be used in semiarid regions of Mexico and USA. Due to the genetic diversity of maize, some lines have developed long mesocotyls capable of deep planting while others are unable to do it. Hence, the genetic and phenetic interaction of maize lines with a robust hydrotropic response and higher mesocotyl elongation in response to water scarcity in time of global heating might be used for developing more resilient maize plants.

Earthen mounds in the Głubczyce Forest (SW Poland) – are they prehistoric long-barrows? Geoarchaeology of the Silesian soil record and human-environment interplay in the Holocene

Two earthen mounds, trapezoid in shape, oriented along the W-E/NW-SE axis and located in prominent landscape positions, were recently discovered in the Głubczyce Forest in the loess area of the Głubczyce Plateau (SW Poland). Their resemblance to long-barrows of the Funnel Beaker culture, as yet unknown in this part of Silesia prompted low-invasive research, involving ALS data analysis, magnetic prospection and a study of soil properties. The objective was to determine if these are indeed anthropogenic structures and if so, how and when were they built. The results indicate: 1) a transformation from chernozemic (Phaeozem) to clay-illuvial soil (Luvisol/Retisol) in the Głubczyce Forest area. Similar processes were identified in neighbouring Central European loess regions and linked with prehistoric climate/vegetation changes (the spread of dense, beech-dominant forests). Human management of the landscape (involving sustained deforestation), enabled the patchy preservation of chernozemic soils until the present-day, 2) both mounds are anthropogenic features, built on a Phaeozem using chernozemic soil. Their construction occurred before the soil transformation, i.e. most likely in prehistory. The development of the Głubczyce Forest may have taken place during the Migration period – a time of settlement decline in Silesia, and 3) the Głubczyce Forest bears further traces of anthropogenic activity: ancient agriculture (field systems), funerary practices, forest management and WWII combat.