Effects of soil drought or waterlogging on the morphological traits of the root system and internal root anatomy were studied
in maize hybrids of different drought tolerance. The investigations comprised quantitative and qualitative analyses of a developed
plant root system through determining the number, length and dry matter of the particular components of the root system and
some traits of the anatomical structure of the seminal root. Obtained results have demonstrated a relatively broad variation
in the habit of the root system. This mainly refers, to the number, length and dry matter of lateral roots, developed by seminal
root, seminal adventitious and nodal roots as well as to some anatomical properties of the stele, cortex and metaxylem elements.
Plants grown under waterlogging or drought conditions showed a smaller number and less dry matter of lateral branching than
plants grown in control conditions. The harmful effect of waterlogging conditions on the growth of roots was greater when
compared with that of plants exposed to drought. In the measurements of the root morphological traits, the effect of soil
drought on the internal root anatomical characteristic was weaker than the effect of soil waterlogging. The observed effects
of both treatments were more distinct in a drought sensitive hybrid Pioneer D than in drought resistant Pioneer C one. The
drought resistant hybrid Pioneer C distinguished by a more extensive rooting and by smaller alterations in the root morphology
caused by the stress conditions than drought sensitive hybrid Pioneer D one. Also the differences between the resistant and
the sensitive maize hybrids were apparent for examined root anatomical traits. Results confirm that the hybrid Pioneer D of
a high drought susceptibility was found to be also more sensitive to periodieal soil water excess. A more efficient water
use and a lower shoot to root (S:R) ratio were found to be major reasons for a higher stress resistance of the hybrid Pioneer
C.
The reasons for a different response of the examined hybrids to the conditions of drought or waterlogging may be a more economical
water balance and more favourable relations between the shoot and root dimensions in the drought resistant genotype. The observed
modifications of the internal root structure caused by water deficit in plant tissues may partly influence on water conductivity
and transport within roots.
The results suggest that the morphological and anatomical traits of the maize root system may be used in practice as direct
or indirect selection criteria in maize breeding. 相似文献
In order to clarify the induction of alcohol dehydrogenase (ADH) by anaerobiosis in oat (Avena sativa L.), the seedlings were exposed to anaerobiosis and activity of ADH and ADH isozyme profiles were determined. The anaerobiosis
increased ADH activities in shoots and roots of the seedlings. By day 2, the activity increased 5 and 4 times in the roots
and the shoots, respectively, compared with those under aerobic condition. Based on nondenaturing electrophoresis, ADH isozyme
composition analysis revealed six bands consisting of a dimmer enzyme with submits encoded by three different Adh genes. Changes in staining intensity of the isozymes indicated that the increase in ADH activity in oat under anaerobiosis
resulted from increased enzyme synthesis. 相似文献
Differences between two maize and two triticale genotypes grown in low soil compaction (LSC), moderate soil compaction (MSC) and severe soil compaction (SSC) and with a limited (D) or excess (W) soil water content were observed as a decrease in shoot (S) and root (R) biomass, leaf greening (SPAD) and increase in membrane injury (LI), root and leaf water potential (ψ), photosynthesis (Pn), transpiration (E) and stomata conductance (gS). Close correlations between ψL and ψR, and between differences ψL and ψR (Δψ) were found. Drought or waterlogging with LSC conditions in both maize genotypes resulted in higher WUE than in control plants (LSC C), but under the SSC WUE declined. However, for triticale differences in WUE, between treatments were small and insignificant. In general, changes in markers were greater for genotypes sensitive to the soil compaction (Ankora, CHD-12) than in resistant ones (Tina, CHD-247) and were higher in seedlings grown under SSC conditions.
Abbreviations:ψR, ψL: root and leaf water potential; C: control; D: drought; E: transpiration rate; FWC: field water capacity; gS: stomatal conductance; LSC, MSC, SSC: low, moderate and severe soil compaction; Pn: photosynthesis rate; W: waterlogging 相似文献
Flooding results in major changes in the soil environment. The slow diffusion rate of gases in water limits the oxygen supply,
which affects aerobic root respiration as well as many (bio)geochemical processes in the soil. Plants from habitats subject
to flooding have developed several ways to acclimate to these growth-inhibiting conditions, ranging from pathways that enable
anaerobic metabolism to specific morphological and anatomical structures that prevent oxygen shortage. In order to acclimate
in a timely manner, it is crucial that a flooding event is accurately sensed by the plant. Sensing may largely occur in two
ways: by the decrease of oxygen concentration, and by an increase in ethylene. Although ethylene sensing is now well understood,
progress in unraveling the sensing of oxygen has been made only recently. With respect to the signal-transduction pathways,
two types of acclimation have received most attention. Aerenchyma formation, to promote gas diffusion through the roots, seems
largely under control of ethylene, whereas adventitious root development appears to be induced by an interaction between ethylene
and auxin. Parts of these pathways have been described for a range of species, but a complete overview is not yet available.
The use of molecular-genetic approaches may fill the gaps in our knowledge, but a lack of suitable model species may hamper
further progress. 相似文献
细根在森林生态系统地下碳循环过程中具有核心地位.2007年11月-2009年11月,对华西雨屏区苦竹人工林进行了模拟氮沉降试验.氮沉降水平分别为对照(CK,0 g N·m-2·a-1)、低氮(5 g N·m-2·a-1)、中氮(15 g N·m-2·a-1)和高氮(30 g N·m-2·a-1)处理,研究氮沉降对苦竹人工林细根和土壤根际呼吸的影响.结果表明:不同处理氮沉降下,<1 mm和1~2 mm细根特性差异较大,与< 1 mm细根相比,1~2 mm细根的木质素、磷和镁含量更高,而纤维素、钙含量更低;氮沉降显著增加了<2 mm细根生物量,对照、低氮、中氮和高氮处理的细根生物量分别为(533±89)、(630±140)、(632±168)和(820±161) g·m-2,氮、钾、镁元素含量也明显增加;苦竹林各处理年均土壤呼吸速率分别为(5.85±0.43)、(6.48±0.71)、(6.84±0.57)和(7.62±0.55) t C·hm-2·a-1,氮沉降对土壤呼吸有明显的促进作用;苦竹林的年均土壤呼吸速率与<2 mm细根生物量和细根N含量呈极显著线性相关.氮沉降使细根生物量和代谢强度增加,并通过增加微生物活性促进了根际土壤呼吸. 相似文献
Of the 643 legume genera, few have been exploited in agriculture and 40% have not even been evaluated for their ability to nodulate and fix nitrogen. Most of these are in tropical/subtropical regions, with habitats ranging from extremely dry to flooded. Recent work in some of these areas shows that plants can nodulate under conditions previously thought to be disadvantageous. The accepted dogma that nitrogen fixing legumes have a high demand for P is challenged and examples of how legumes can extract P from soils with low available P described. Species tolerant to shading and high soil Al are cited, although the mechanisms of adaptation are not yet clear. Some tropical soils have high nitrate levels and, contrary to perceived wisdom, there are legumes which can nodulate under such conditions. Many tropical tree legumes prefer ammonium to nitrate and are able to fix nitrogen and assimilate ammonium at the same time. In all these cases, there are genotypic differences, both within and among species.
Large areas of tropical fresh water, such as the Brazilian Pantanal and the Orinoco floodplain have nodulated legumes predominant in their flora. The ecological potential of these has not been evaluated. One of the sites of nodule evolution is likely to have been in such areas. Modes of infection of legumes by rhizobia vary with taxonomic tribe and may represent evolution for survival in different environments. As more legumes, from more ecosystems are studied, a wider range of adaptations is likely to be found. Work is urgently needed to study these, especially in areas being cleared for agriculture or by logging. 相似文献