Soil Chemical Analysis

Zinc (Zn) is an essential component of thousands of proteins in plants, although it is toxic in excess. In this review, the dominant fluxes of Zn in the soil-root-shoot continuum are described, including Zn inputs to soils, the plant availability of soluble Zn(2+) at the root surface, and plant uptake and accumulation of Zn. Knowledge of these fluxes can inform agronomic and genetic strategies to address the widespread problem of Zn-limited crop growth. Substantial within-species genetic variation in Zn composition is being used to alleviate human dietary Zn deficiencies through biofortification. Intriguingly, a meta-analysis of data from an extensive literature survey indicates that a small proportion of the genetic variation in shoot Zn concentration can be attributed to evolutionary processes whose effects manifest above the family level. Remarkable insights into the evolutionary potential of plants to respond to elevated soil Zn have recently been made through detailed anatomical, physiological, chemical, genetic and molecular characterizations of the brassicaceous Zn hyperaccumulators Thlaspi caerulescens and Arabidopsis halleri.

Zinc in plants

Drought is one of the major constraints limiting crop production worldwide. Crop growth models predict that this issue will be more severe in future. Drought impairs normal growth, disturbs water relations, and reduces water use efficiency in plants. Plants, however, have a variety of physiological and biochemical responses at cellular and whole organism levels, making it a more complex phenomenon. The rate of photosynthesis is reduced mainly by stomatal closure, membrane damage, and disturbed activity of various enzymes, especially those involved in ATP synthesis. Plants display a range of mechanisms to withstand drought, such as reduced water loss by increased diffusive resistance, increased water uptake with prolific and deep root systems, and smaller and succulent leaves to reduce transpirational loss. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols also play vital roles in sustaining cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberellins, cytokinins, and abscisic acid modulate plant responses toward drought. Polyamines, citrulline, and several enzymes act as antioxidants and reduce adverse effects of water deficit. Plant drought stress can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection, and exogenous application of hormones and osmoprotectants to seeds or growing plants, as well as engineering for drought resistance. Here, we provide an overview of plant drought stress, its effects on plants’ resistance mechanisms and management strategies to cope with drought stress.

Drought stress in plants: an overview

Farmers' prioritization of climate-smart agriculture (CSA) technologies

Effects of drought stress and N supply on the growth, biomass partitioning and water-use efficiency of Sophora davidii seedlings

Growth of Dalbergia sissoo in desert regions of western India using municipal effluent and the subsequent changes in soil and plant chemistry.

Growth and mineral accumulation in Eucalyptus camaldulensis seedlings irrigated with mixed industrial effluents

Nutrients used for plant growth and biomass productions generally come from the internal cycling of reserve materials which require water for their solubilization and translocation. Nutrient absorption is governed by the interaction occurring at the soil-root interface, including (a) root morphology and growth rate, (b) nutrient absorption kinetics of the root; and (c) soil nutrient supply (Guiterrez-Boem & Thomas 1999). Decrease in soil water availability affects the rate of diffusion of many plant nutrients and finally the composition and concentration of soil solution. Over a period of water stress a marked decrease in nutrient uptake is reported (Marschner 1986) through decreased transfer of ions to the root. Thus, it will be of significant use to quantify the level of water stress above which the mobilization and absorption of nutrients are adversely affected. Dalbergia sissoo Roxb was the selected species because of its timber value and social acceptability in the arid and semiarid areas of western India. The objective of this study was to determine the effect of soil water stress on the availability of soil nutrients, their distribution in different parts and total nutrient uptake by D. sissoo seedlings. The experiment was carried out at the experimental farm of Arid Forest Research Institute (AFRI) Jodhpur (26° 45′ N latitude and 72° 03′ E longitude). Mean monthly minimum and maximum temperature was 10.0°C and 41.3°C, respectively during the experimental period. Rainfall was 237 mm and total pan evaporation was 2109 mm (August 1998 to May 1999). Soil was a loamy sand (coarse loamy, mixed hyperthermic family of Typic Haplocambids) and had pH 8.3, EC 0.5 dSm1 and organic carbon 0.18%. Soil water content at field capacity (-0.03 MPa) was 10.7% (w/w) and 3.2% at –1.5 MPa. The soil had 91.5% sand, 7.1% silt and 1.4% clay and low nitrogen and available phosphorus. Four months old seedlings of Dalbergia sissoo was used in the study. Seedlings were planted in galvanized iron containers of 45 m diameter and 55 m depth, filled with 120 kg loamy sand soil. At the time of treatment application, average seedling height and collar diameter were 52 cm and 0.4 cm, respectively. The experiment had five treatments comprising varying water stress in terms of irrigation levels. Each treatment was taken in eight replications and experiment was laid in Randomized Complete Block Design. Soil of all the containers was fully saturated by addition of 82.0 mm water in the first week of October 1998 after proper establishment of the seedlings. Drainage of excess water was allowed till the soil water ceased to drain down. Soil water content was continuously monitored gravimetrically (sampling of soil each time) after oven drying of the soil samples at 110°C temperature to a constant weight. Irrigation levels were defined on the basis of soil water content at suction pressures of –0.03 MPa (10.7%), -0.05 MPa (9.9%), -0.10 MPa (7.4%), 0.50 MPa (5.6%), -1.00 MPa (4.3%) and –1.50 MPa

Genda Singh

Papers

Growth of Dalbergia sissoo in desert regions of western India using municipal effluent and the subsequent changes in soil and plant chemistry.

Growth and mineral accumulation in Eucalyptus camaldulensis seedlings irrigated with mixed industrial effluents

Influence of soil water regime on nutrient mobility and uptake by Dalbergia sissoo seedlings

Effects of controlled irrigation on water potential, nitrogen uptake and biomass production in Dalbergia sissoo seedlings

Plant growth, biomass production and soil water dynamics in a shifting dune of Indian desert