Shahzad Maqsood Ahmed Basra

Plant Drought Stress: Effects, Mechanisms and Management

Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

RETRACTED: Chapter 6 Strategies for Producing More Rice with Less Water

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Seed priming improves growth of nursery seedlings and yield of transplanted rice

Abstract An attempt to improve the performance of rice (Oryza sativa L.) nursery seedlings through seed priming and its effect on the yield after transplantation was made in a field trial. Priming tools employed during the investigation include pre-germination, hydropriming for 48 h, osmohardening with KCl and CaCl2 (ψs-1.25 MPa) for 24 h, vitamin priming with 10 ppm ascorbic acid for 48 h and seed hardening for 24 h. All the priming techniques resulted in improved germination speed and spread, seedling fresh and dry weight, root and shoot length, number of secondary roots, seedling nitrogen, total sugars and α-amylase activity. Osmohardening with CaCl2 resulted in the best performance as indicated by improved germination speed and spread, seedling vigour and starch metabolism, followed by hardening and osmohardening with KCl. However, improved starch metabolism in coarse rice was observed in osmohardening with KCl. Higher K and Ca contents were observed in seeds osmohardened with KCl and CaCl2, respectively. Maximum straw and kernel yield and harvest index were recorded from osmohardening with CaCl2 in fine and osmohardening with KCl in coarse rice. Increased number of secondary roots and α-amylase activity were accompanied with increased seedling nitrogen and reducing sugars, respectively.

Performance of Late Sown Wheat in Response to Foliar Application of Moringa oleifera Lam. Leaf Extract

Aumento en temperatura durante inicios de primavera induciendo madurez temprana es un factor clave en la reduccion de rendimiento en siembra tardia de trigo (Triticum aestivum L.). Las hojas de Moringa oleifera Lam. son ricas en zeatina, una citoquinina que tiene rol en retraso de senescencia foliar, ademas de otros compuestos que mejoran crecimiento como ascorbatos, fenoles, y minerales. Este estudio se planeo para optimizar dosis y estado de crecimiento optimo para extracto foliar de moringa (MLE) aplicado foliarmente y su rol en retraso de senescencia foliar en siembra tardia de trigo. El cultivo de trigo se sembro el 16 de septiembre y MLE (diluido 30 veces) se aplico en diferentes estados de crecimiento desde macollamiento hasta espigadura y en espigadura, mientras se asperjo agua destilada como control. En resultados todos los tratamientos MLE fueron mejores que el control. Sin embargo, un aumento de 10,73; 6,00; 10,70 y 4,00% fue evidente en peso de 1000 granos, rendimiento biologico, produccion de grano e indice de cosecha, respectivamente, con aspersion de MLE en macollamiento + encanado + estado de bota + espigadura. Aspersion de MLE solo en espigadura dio 6,84; 3,17 y 3,51% mas de peso 1000 granos, rendimiento biologico, produccion de grano, e indice de cosecha respectivamente, comparado con control. MLE extendio la duracion del area foliar estacional (LAD estacional) en 9,22 y 6,45 d sobre el control cuando se aplico a todos los estados de crecimiento y aspersion a espigadura, respectivamente. Concluimos que posiblemente debido a la presencia de sustancias, la aspersion foliar de MLE puede retrasar la madurez de cultivo, extender LAD estacional y periodo de llenado de grano conduciendo, por lo tanto, a mayores producciones de semilla y biologica en trigo sembrado tardiamente.

Rice Seed Invigoration: A Review

Rice (Oryza sativa L.) provides about 55–80% of the total calories for people in South Asia, Southeast Asia, and Latin America. Elsewhere, it represents a high-value commodity crop. Change in the method of crop establishment from traditional manual transplantation of seedlings to direct seeding has been adopted in many Asian countries in the last two decades, in view of rising production costs, especially for labor and water. Seed invigoration is ascribed to beneficial treatments, applied to the seeds after harvest but prior to sowing, that improve germination or seedling growth or facilitate the delivery of seeds and other materials required at the time of sowing. Many seed invigoration treatments are being employed in a number of field crops, including rice, to improve seedling establishment under normal and stressful conditions. The treatments used to invigorate rice seed include hydropriming, seed hardening, on-farm priming, osmopriming, osmohardening, humidification, matripriming, priming with plant growth regulators, polyamines, ascorbate, salicylicate, ethanol, osmolytes, coating technologies, and more recently presowing dry heat treatments. In the wake of the day-to-day increasing cost of labor and shortage of water, direct seeding approaches in rice cropping systems are the subject of intensive investigation throughout the world and offer an attractive alternative to traditional rice production systems. In this regard, seed invigoration techniques are pragmatic approaches to achieving proper stand establishment in the new rice culture. They help in breaking dormancy and improving seedling density per unit area under optimal and adverse soil conditions. Induction and de novo synthesis of hydrolases, such as amylases, lipases, proteases; and antioxidants such as catalases, superoxide dismutase and peroxidases are reported to be the basis of improved performance using these techniques. The rice seed priming can be performed by soaking simply in water, a solution of salts, hormones, osmoprotectants, matric strain-producing materials, and other nonconventional means. Despite certain limitations, such as water potential, oxygen and temperature, rice seed invigoration has been worthwhile in improving rice yield and quality. Nevertheless, in-depth studies are imperative for understanding the physiological and molecular basis of rice seed priming.

Comparison of conventional puddling and dry tillage in rice–wheat system

In many parts of Asia, rice is transplanted in puddled fields and after the harvest of this crop wheat is grown. This traditional method of growing rice may have deleterious effect on the growth of the subsequent crop in a rice–wheat cropping system. Wheat crop was planted in the same plots following a rice crop to evaluate the residual effects of various tillage treatments suitable for rice on the growth of the subsequent crop. Rice cultivar Super-basmati was grown in summer and wheat cultivar Auqab-2000 in autumn after rice. Four treatments were used to grow rice viz. transplanting in continuously flooded conditions (TRF), transplanting with intermittent flooding and drying (TRI), direct seeded using dry seeds (DSR) and direct seeded using primed seeds (DSP). Traditional puddling tillage system was followed in TRF and TRI, while for DSR and DSP, dry tillage system was followed. For convenience, the abbreviations of the rice treatments were used to indicate the same plots during the wheat crop. For the rice crop, tiller number, fertile tillers, kernel and straw yield, and harvest index were significantly better with transplanted treatments (TRI and TRF) than the direct seeded treatments. TRI also gave a yield advantage of 5% over TRF. For wheat, crop following direct seeded rice was better than transplanting. This study suggests that intermittent irrigation in the traditional puddling tillage system and DSP dry tillage system are the promising alternatives that may be opted.

Seed Priming Influence on Early Crop Growth, Phenological Development and Yield Performance of Linola (Linum usitatissimum L.)

Reduced early crop growth and limited branching are amongst yield limiting factors of linola. Field response of seed priming treatments viz. 50 mmol L−1 salicylic acid (SA), 2.2% CaCl2 and 3.3% moringa leaf extract (MLE) including untreated dry and hydropriming controls was evaluated on early crop growth and yield performance of linola. Osmopriming with CaCl2 reduced emergence time and produced the highest seedling fresh and dry weights including Chl. a contents. Osmopriming with CaCl2 reduced crop branching and flowering and maturity times and had the maximum plant height, number of branches, tillers, pods and seeds per pod followed by MLE. Increase in seed weight, biological and seed yields was 9.30, 34.16 and 39.49%, harvest index (4.12%) and oil contents (13.39%) for CaCl2 osmopriming. Positive relationship between emergence and seedling vigor traits, 100-seed weight, seed yield with maturity time, 100-seed weight and seed yield were found. The study concludes that seed osmopriming with CaCl2 or MLE can play significant role to improve early crop growth and seed yields of linola.

Biomass production and nutritional quality of Moringa oleifera as a field crop

Wasif NOUMAN*, Muhammad Tahir SIDDIQUI, Shahzad Maqsood Ahmed BASRA, Hasnain FAROOQ, Muhammad ZUBAIR, Tehseen GULL 1 Department of Forestry, Range and Wildlife Management, Bahauddin Zakariya University Multan, Pakistan 2 Department of Forestry, Range Management and Wildlife, University of Agriculture Faisalabad, Pakistan 3 Department of Crop Physiology, University of Agriculture Faisalabad, Pakistan College of Agriculture, Dera Ghazi Khan, Sub-Campus University of Agriculture Faisalabad, Pakistan 5 Department of Chemistry, University of Agriculture Faisalabad, Pakistan

Seed Priming with Polyamines Improves the Germination and Early Seedling Growth in Fine Rice

ABSTRACT Pre-sowing polyamine seed treatments were employed in fine rice (Oryza sativa) to explore the possibility of improving germination and early seedling growth. Fine rice (cv. Super-basmati) seeds were soaked in 10 and 20 ppm aerated solutions of spermidine, putrescine and spermine for 48-h at 28 ± 2 C. Polyamine seed treatments resulted in earlier, synchronized and enhanced germination. Improvement in shoot and root length, seedling fresh and dry weight, and root and leaf score, was also observed in seeds treated with polyamines. Seed treatment with 10 ppm putrescine solution was the most effective for most of the attributes studied.

Zinc bioavailability response curvature in wheat grains under incremental zinc applications

Zinc application is generally recommended to enrich wheat grains with Zn; however, its influence on Zn bioavailability to humans has not received appreciable attention from scientists. In this pot experiment, seven Zn rates (from 0 to 18 mg kg−1 soil) were applied to two wheat cultivars (Shafaq-2006 and Auqab-2000). Application of Zn significantly increased grain yield, grain Zn concentration and estimated Zn bioavailability, and significantly decreased grain phytate concentration and [phytate]:[Zn] ratio in wheat grains. The response of grain yield to Zn application was quadratic, whereas maximum grain yield was estimated to be achieved at 10.8 mg Zn kg−1 soil for Shafaq-2006 and 7.4 mg Zn kg−1 soil for Auqab-2000. These estimated Zn rates were suitable for increasing grain Zn concentration and Zn bioavailability (>2.9 mg Zn in 300 g grains) to optimum levels required for better human nutrition. Conclusively, Zn fertilization for Zn biofortification may be practiced on the bases of response curve studies aimed at maximizing grain yield and optimum Zn bioavailability. Moreover, additive Zn application progressively reduced the grain Fe concentration and increased the grain [phytate]:[Fe] ratio. However, a medium Zn application rate increased grain Ca concentration and decreased the grain [phytate]:[Ca] ratio. Hence, rate of Zn application for mineral biofortification needs to be carefully selected.