Shahid Farooq

Boron Application Improves Growth, Yield and Net Economic Return of Rice

A field trial was conducted to evaluate the role of boron (B) application at different growth stages in improving the growth, yield and net economic return of rice at farmers fields during summer season, 2009. Boron was soil applied (1.5 kg/hm 2 ) at the transplanting, tillering, flowering and grain formation stages of rice; foliar applied (1.5% B solution) at the tillering, flowering and grain formation stages of rice, and dipped seedling roots in 1.5% B solution before transplanting; while control plots did not apply any B. Boron application (except dipping of seedling roots in B solution, which caused toxicity and reduced the number of tillers and straw yield than control) substantially improved the rice growth and yield. However, soil application was better in improving the number of grains per panicle, 1000-grain weight, grain yield, harvest index, net economic income and ratio of benefit to cost compared with the rest of treatments. Overall, for improving rice performance and maximizing the net economic returns, B might be applied as soil application at flowering.

Higher Tolerance to Abiotic Stresses and Soil Types May Accelerate Common Ragweed (Ambrosia artemisiifolia) Invasion

Common ragweed is a troublesome allergenic invader and noxious weed of several crops. Despite extensive research to understand the factors affecting its invasion, the role of environmental stresses and soil types on survival and growth is poorly understood. The objective of this study was to determine the effects of drought, salinity, and soil types on survival, growth, and nutrient uptake of ragweed in greenhouse experiments to predict its invasiveness in Turkey. Three separate experiments, with five drought intensities (100, 75, 50, 25, and 12.5% of field capacity [FC]), four levels of salinity (0, 3, 6, and 12 dS m-1), and five soil types varying in sand, silt, and clay content were performed. Severe drought and salinity levels reduced seedling survival, while soil type had no effect. Increasing drought and salinity negatively affected growth and nutrient uptake; the poorest growth was observed under severe drought intensity. Ragweed exhibited intensive tolerance to drought, even severe levels, while it tolerated salinity up to 6 dS m-1 for seedling survival. Growth was negatively affected above 3 dS m 1. The highest and lowest nutrient accumulations were recorded under moderate and extreme drought intensities, respectively. Similarly, the highest Na accumulation was observed under extreme saline conditions, whereas the highest P uptake and K/Na ratio were achieved under nonsaline conditions (0 dS m-1). Variation of soil texture had no effect on growth and nutrient uptake. The highest Ca, Mg, and Na accumulations were recorded on clay soil, while higher P accrued on sandyloam soil. Increased tolerance of ragweed to severe drought and moderate salinity and its nonselective nature for soil type indicate that semiarid and partially arid regions in Turkey have plenty of vacant niches for ragweed invasion. Nomenclature: Ragweed, Ambrosia artemisiifolia L. AMBEL

Invasion Potential of Two Tropical Physalis Species in Arid and Semi-Arid Climates: Effect of Water-Salinity Stress and Soil Types on Growth and Fecundity.

Invasive plants are recognized for their impressive abilities to withstand adverse environmental conditions however, all invaders do not express the similar abilities. Therefore, survival, growth, nutrient uptake and fecundity of two co-occurring, invasive Physalis species were tested under water and salinity stresses, and different soil textures in the current study. Five different water stress levels (100, 75, 50, 25, and 12.5% pot water contents), four different soil salinity levels (0, 3, 6, and 12 dSm-1) and four different soil textures (67% clay, 50% clay, silt clay loam and sandy loam) were included in three different pot experiments. Both weeds survived under all levels of water stress except 12.5% water contents and on all soil types however, behaved differently under increasing salinity. The weeds responded similarly to salinity up till 3 dSm-1 whereas, P. philadelphica survived for longer time than P. angulata under remaining salinity regimes. Water and salinity stress hampered the growth and fecundity of both weeds while, soil textures had slight effect. Both weeds preferred clay textured soils for better growth and nutrient uptake however, interactive effect of weeds and soil textures was non-significant. P. angulata accumulated higher K and Na while P. philadelphica accrued more Ca and Mg as well as maintained better K/Na ratio. P. angulata accumulated more Na and P under salinity stress while, P. philadelphica accrued higher K and Mg, and maintained higher K/Na ratio. Collectively, highest nutrient accumulation was observed under stress free conditions and on clay textured soils. P. philadelphica exhibited higher reproductive output under all experimental conditions than P. angulata. It is predicted that P. philadelphica will be more problematic under optimal water supply and high salinity while P. angulata can better adapt water limited environments. The results indicate that both weeds have considerable potential to further expand their ranges in semi-arid regions of Turkey.

THE IMPACT OF SEED PRIMING AND ROW SPACING ON THE PRODUCTIVITY OF DIFFERENT CULTIVARS OF IRRIGATED WHEAT UNDER EARLY SEASON DROUGHT

This study was conducted to improve wheat production under vegetative (early season) drought stress. Hydroprimed and osmoprimed (with CaCl 2 ) seeds of wheat cultivars Lasani-2008 (LS-2008) and Triple Dwarf-1 (TD-1), were sown in 20 (narrow), 25 (medium), and 30 cm (wider) spaced rows. Crop was grown under well-watered conditions till physiological maturity or was subjected to drought stress (50% field capacity) during vegetative phase and then grown under well-watered conditions. Drought stress caused substantial reduction in grain and biological yields, related traits, harvest index (HI) and water use efficiency (WUE). Nonetheless, planting osmoprimed seeds in narrowly spaced rows significantly improved the grain yield, HI and WUE. However, wheat planted in wider rows had bold grains. Furthermore, wheat cultivar LS-2008 produced better yield, even under drought stress, than cultivar TD-1. Economic analysis indicated that planting osmoprimed seeds of wheat cultivar LS-2008 in narrowly spaced rows under early season drought yielded maximum economic benefits. In conclusion, planting osmoprimed seeds of cultivar LS-2008 in narrowly spaced rows is a good agronomic option to improve the wheat performance under early season drought stress.

Germination Biology of Two Invasive Physalis Species and Implications for Their Management in Arid and Semi-arid Regions

Two Solanaceae invasive plant species (Physalis angulata L. and P. philadelphica Lam. var. immaculata Waterfall) infest several arable crops and natural habitats in Southeastern Anatolia region, Turkey. However, almost no information is available regarding germination biology of both species. We performed several experiments to infer the effects of environmental factors on seed germination and seedling emergence of different populations of both species collected from various locations with different elevations and habitat characteristics. Seed dormancy level of all populations was decreased with increasing age of the seeds. Seed dormancy of freshly harvested and aged seeds of all populations was effectively released by running tap water. Germination was slightly affected by photoperiods, which suggests that seeds are slightly photoblastic. All seeds germinated under wide range of temperature (15–40 °C), pH (4–10), osmotic potential (0 to −1.2 MPa) and salinity (0–400 mM sodium chloride) levels. The germination ability of both plant species under wide range of environmental conditions suggests further invasion potential towards non-infested areas in the country. Increasing seed burial depth significantly reduced the seedling emergence, and seeds buried below 4 cm of soil surface were unable to emerge. In arable lands, soil inversion to maximum depth of emergence (i.e., 6 cm) followed by conservational tillage could be utilized as a viable management option.

The Influence of Environmental Factors on Germination of Burcucumber (Sicyos angulatus) Seeds: Implications for Range Expansion and Management

Abstract Burcucumber (Sicyos angulatus L.) is a highly invasive vine that has become naturalized in the humid Black Sea region of Turkey, but previous to this study there was no information on the germination biology of this weed. The germination biology of three naturalized populations of S. angulatus from the Black Sea region was studied in laboratory and greenhouse experiments. The germination of nondormant seeds was observed under different photoperiods, constant temperatures, and varying levels of pH, salinity, and osmotic potential. Furthermore, seedling emergence from various soil depths was investigated. The seeds of all populations proved nonphotoblastic (82% to 90%, 55% to 66%, and 48% to 56% germination under 12-, 24-, and 0-h photoperiod, respectively) and germinated over a wide range of temperatures (5 to 40 C). Seedlings emerged from all seed burial depths (0 to 15 cm); however, germination was drastically reduced (>90% reduction) beyond 6 to 8 cm. Seed germination was 30% to 38% for seeds placed on the surface and increased to 78% to 88% for seeds buried 2 cm deep, while germination was severely reduced for seeds buried 10 and 15 cm deep (8 to 12% and 0 to 6%, respectively). Seeds of all populations were found to be sensitive to osmotic and salinity stress and to highly acidic and alkaline pH levels. All populations had similar requirements for germination that are directly related to their area of naturalization. These results indicate that the species has limited potential for range expansion to arid, semiarid (nonirrigated), and relatively saline areas. However, humid, salinity-free, and frequently irrigated areas of the country are at high risk of invasion. In arable lands, deep tillage followed by shallow tillage and effective management of emerging seedlings could deplete the soil seedbank in the long run. However, there is an urgent need for effective strategies to manage the species in other nonarable areas.

Nutrient Homeostasis and Salt Stress Tolerance

Soil salinity is an unavoidable constraint in crop production globally. Soil salinization is often caused by improper soil management and/or crop production practices, which has made highly productive lands barren/unusable. Plant species have evolved several mechanisms to cope with salinity stress. Nutrient homeostasis is among the different mechanisms employed by plant species to withstand elevated salt levels in the root zone. Nutrients are the mediators of metabolism, so their cytoplasmic levels need to be effusively controlled both under stressful and benign environments. Several studies report the homeostasis of a single ion, i.e., sodium, potassium, or chloride. However, limited studies are available reporting the role of nutrient homeostasis (all nutrients together) under salinity stress. This chapter describes the role of nutrient homeostasis and ion channels and transporters in salt stress tolerance of plant species. The ion efflux at plasma membrane and vacuolar compartmentation in response to salinity stress has been described in detail. The impaired uptake of the nutrients is an obvious effect of salinity, mainly disturbing the sodium and potassium uptake. Much of the research has been done to test the role of different nutrients on salinity alleviation, and silicon is found to alleviate the negative effects of salinity. The nutrient homeostasis starts from ion sensing, uptake, transport, and activation of defense mechanisms as well as regulation of genes or gene networks to alleviate/withstand the adverse effects of salinity. Thus, the ion sensing, uptake, transport, and gene defense activation in response to salinity stress have also been described comprehensively.

Mechanical Weed Control

Abstract Evolution of herbicide resistance in weeds has increased the importance and scope of mechanical weed control. In many parts of the world, the efficacy of mechanical weed control has been reevaluated. Tillage (used for soil preparation for planting), although among the oldest methods of weed control, is still the preferred method of weed control for many farmers. Similarly, subsequent weeding (weed removal through manual or mechanical means) after the crop emergence is also a successful tool for effective weed management. Wise use of mechanical weeding can provide effective weed control in vegetables, fruits, and field crops. The use/choice of mechanical weeding method depends upon technical and economic factors. Weeds evolving herbicide resistance ultimately required either tillage, weeding, or other non-chemical methods; nevertheless, tillage has been considered the most effective among all non-chemical weed control methods. Development of intelligent weeders or automatic weeding tools may revolutionize mechanical weed control through the selective use of weeders in crops. However, a great deal of research work and investment is needed to develop robotic weeders, which are capable of functioning without human intervention for automated weed control in the future.

Impact of Abiotic Stresses on Grain Composition and Quality in Food Legumes

Grain quality and composition in food legumes are influenced by abiotic stresses. This review discusses the influence of abiotic stresses on grain composition and quality in food grains. Grain protein declines under salt stress due to the restricted absorption of nitrate from the soil solution. Grain phosphorus, nitrogen, and potassium contents declined whereas sodium and chloride increased. However, under drought, grain protein increased whereas the oil contents were decreased. For example, among fatty acids, oleic acid content increased; however, linoleic and/or linolenic acids were decreased under drought. Heat stress increased grain oil content whereas grain protein was decreased. Low temperature during late pod-filling reduced starch, protein, soluble sugar, fat, and fiber contents. However, an elevated CO2 level improved omega-3 fatty acid content at the expense of omega-6 fatty acids. Crop management and improvement strategies, next generation sequencing, and gene manipulation can help improve quality of food legumes under abiotic stresses.