Sequence of drought response of maize seedlings in drying soil

Abstract

Leaf elongation in monocotyledonous plants is sensitive to drought. To better understand the sequence of events in plants subjected to soil drying, leaf elongation and transpiration of maize seedlings (Zea mays L.) of 4 cultivars were monitored continuously and the diurnal courses of the root and leaf water relations were determined. Results from this study indicate the following sequence of drought response: Leaf elongation decreased before changes in the leaf water relations of non‐growing zones of leaf blades were detected and before transpiration decreased. Reductions in leaf elongation preceded changes in the root water potential (ψw). Root ψw was not a very sensitive indicator of soil dryness, whereas the root osmotic potential (ψs) and root turgor (ψp) were more sensitive indicators. The earliest events observed in drying soil were a significant increase in the largest root diameter class (1 720 to 1 960 gm) and a decrease in leaf elongation (P= 0.08) 2 days after withholding water. Significant increases in root length were observed 2 days later. Soil drying increased the number of fine roots with diameters of <240 µm. Slight increases in soil strength did not affect leaf elongation in the drying soil.

Interactive Effects of N-, P- and K-Nutrition and Drought Stress on the Development of Maize Seedlings

“…The enhanced root growth may be able to explore and absorb more water and nutrients from the soil [8,24,46]. The lower shoot DW with N, NP and NPK fertilization may be due to an increase in assimilate allocation to roots for maintaining root growth, for osmotic adjustment and for turgor maintenance [10,25,26]. Similar results were reported by other authors [21,47,48].…”

“…Consequently, the root/shoot ratios were significantly increased with N, NP, PK and NPK supply under drought conditions compared with well-watered conditions (Figure 7). Possibly, with the development of less soil moisture, plants respond to drought by increasing root biomass or a root absorptive surface relative to the shoot biomass [25,26,30]. The enhanced root growth may be able to explore and absorb more water and nutrients from the soil [8,24,46].…”

“…At the seedling growth stage, drought stress might result in higher root dry weights and longer roots and/or reduced shoot growth [1,[24][25][26][43][44][45]. Although our study did not show a significant increase in root DW or a significant decrease in shoot DW under drought stress for all nutrient treatments, the results in Figures 4 and 6 demonstrated that there was a tendency of higher root DW for all nutrient treatments except for NK fertilization at day 20 after sowing and of lower shoot DW for single N and combined NP and NPK under drought than under well-watered conditions.…”

Xylem embolism and drought-induced stomatal closure in maize

“…The two pairs of genotypes we evaluated were provided by maize breeders on the basis of their grain yield under drought conditions. Schmidhalter et al (1998) have shown that, in maize, growth is reduced before any appreciable change in water relations has occurred. Therefore, there is probably little reason for growth performance under drought conditions to be correlated with hydraulic traits, such as cavitation avoidance, that manifest at much higher water stress levels.…”

Water uptake under water stress at panicle initiation stage in upland rice as affected by previous soil water regimes

“…However, the substantial decrease of the ch values during the stress period in both DP and WP (Table 3) suggested that the rapid decrease of the q values could not be fully attributed to the reduction of the transpirational demand. In previous studies it was found that the ch value increased to a similar level to that of (Reicosky and Ritchie 1976;Schmidhalter et al 1998;Ameglio et al 1999). If the daily plant water uptake were limited only by the reduction of the transpirational demand due to the leaf stomatal closure or leaf rolling, the decrease in the CPL value at pre-dawn should be similar to that in CPs.…”