Search

The performance of gynoecious cucumber (cv. Terminator) was evaluated under three protected structures viz., naturally ventilated polyhouse (NVP), insect proof net house (INH) and shade net house (SNH) at Jodhpur, Rajasthan in hot arid region of India. The photosynthetically active radiation (PAR) inside these structures during cropping period ranged from 154-842 μmol m-2 s-1 which was much lower than the outside. Among structures, air temperature was 1.2°C and 0.7°C lower while relative humidity (RH) was 17 and 4 per cent higher in NVP and SNH respectively as compared to INH. Relatively low air as well as soil temperature, coupled with high RH and optimal radiation in NVP led to better plant growth and physiological activity which resulted in 42 and 142per cent higher yield than INH and SNH, respectively. Hence, it can be recommended that NVP is the best low-tech protected structure which modifies the microclimate favouring successful cultivation of greenhouse cucumber in Indian hot arid regions.

Increasing fertilizer demands and dwindling mineral reserves warrant sustainable alternatives for plant fertilization. Organo-mineral fertilizers (OMFs) based on indigenous materials which are unutilized commercially are a possible option. The study describes the effect of novel OMF of phosphorus (OMF-P) and potassium (OMF-K), developed respectively from insoluble low-grade rock phosphate and feldspar on plant growth. The experiment was conducted in a glass chamber partitioned into two blocks, one with soil and the other with soil supplemented with 1% OMF-P or 1% OMF-K. Pearl millet plants were grown in the chambers for 45 days and the roots and soil from different chamber blocks were separated and analyzed. Root volume, fresh and dry weights, average root length, diameter and number of root tips were significantly increased with OMF-P/OMF-K and plants showed improved growth and plant height. The release and availability of P/K in soil was confirmed with isolations of P- and K-solubilizing fungi from the blocks with OMF along with significantly higher values of available P (0.006 mg g−1) and K (0.01 mg g−1) recorded from these blocks compared to control chambers. Moreover, the OMF prills did not exhibit any adverse effects on the plants and on soil microflora. The release of soluble P and K from the OMF is attributed to the presence of P and K solubilizers in soil, since conditions favourable for their selective enrichment are created. The OMF prills developed could address issues of deteriorating mineral reserves and associated environmental degradation, besides providing a sustainable management option.

Plants and microorganisms sense and respond to biotic and abiotic signals in the environment to competitively optimize their fitness. These specific adjustments which are pertinent to prevailing en...

In present context and under foreseeing scenario of climate change, the declining of water allocation to agriculture due to increase of population and food demand has sensitized judicious use of available water in agriculture. Under such scenario, maximization of crop water productivity is more crucial than simple yield maximization – a target usually anticipated under irrigated condition. Deficit irrigation (DI) has been proposed as a valuable strategy of economizing water use, more particularly in water scarce arid and semi-arid regions. Available literature suggests that appropriate DI strategy may account for a significant amount of water saving with some improvement in fruit quality such as in tomato, one of the most nutritious and economic vegetables of global significance. In present review, varying aspects of DI in tomato are discussed: tactful (growth-stage/-period wise) implementation of DI strategies to attain satisfactory level of water saving without or with a minimum penalty on economic yield and quality; various morphological and physio-biochemical implications of DI in tomato plants relevance to conservative use of water; the integrated approach involving different agronomic practices with DI; and the future prospects of DI, and its combination with other approaches for sustainable tomato cultivation is also highlighted.

Protected vegetable cultivation is a fast-growing sector in which grafting plays a crucial role for success. Cucumber is predominantly grown under protected conditions. The popular slicing (mini) cucumber comprises two segments, single- and cluster-fruit-bearing. In the present study, the performance of select fruit-bearing hybrids grafted as scions onto commercial Cucurbita hybrid rootstock ‘NS-55’ was evaluated under three different low-cost protected structures in arid regions. With respect to type of protected structure, cucumber performance was superior under a naturally ventilated polyhouse (NVP) than an insect net house (INH) or a shade net house (SNH). Micro-climate parameters inside NVP (air temperature, RH and PAR) were more congenial for cucumber than those in net houses, thereby facilitating improved physiology (chlorophyll fluorescence, chlorophyll and plant water potential) and leaf mineral status. Grafting invariably improved growth and yield parameters under all protected structures. Overall plant performance was better in the grafted cluster-fruit-bearing hybrid ‘Terminator’ than the single-fruit-bearing hybrid ‘Nefer’ or their non-grafted counterparts. Furthermore, NVP was found to be superior to net houses for water productivity, and grafted plants were more water use efficient than their counterpart non-grafted plants. Thus, NVP can be considered a suitable low-cost protected structure in conjunction with grafting to boost cucumber crop and water productivity in arid regions.

The present study is an attempt to assess the spatial variability and the changes in the population of Prosopis cineraia (khejri) trees in the agroforestry systems of arid part of western Rajasthan. This tree is regarded as an important natural resource for the rural livelihood of desert dwellers because of its multifarious uses. The tree populations were mapped in a geographical information system using available information from aerial photographs, google earth images and IRS-LISS-III satellite images to compare their populations between the past and the very recent period. Mapping carried out in a part of Nagaur district in western part of Rajasthan, indicated increase in khejri trees in the region in 2013–2014 compared to 1960s. The number and tree density were higher under irrigated croplands than under rainfed. Increase in rainfall, multiple uses of the tree, societal and scientific support are the key reasons for the observed changes in their population.

Nanoparticles possess unique properties such as a large specific surface area and consequently greater reactivity than macro-sized particles. Therefore questions concerning their potential adverse effects on human and environmental health have often been raised. They are being widely used in consumer products and are thus expected to find their way into aquatic, terrestrial, and atmospheric environments, where their fate and behavior are unpredictable. Therefore plants that interact strongly with their immediate environments are expected to be affected as a result of exposure to the nanoparticles. Factors influencing the entry of nanoparticles into a plant cell are shape and size of the nanoparticles in addition to size of the cell wall pore. Selective permeability exercised by the cell membrane also influences the entry as well as surface characteristics, charge, and configuration of nanoparticles. After entering through the cell wall they move from cell to cell either apoplastically or symplastically and in that process they may reach locations that are far from the application point. Aggregation of metallic nanoparticles can be further guided by external magnetic forces and this forms the basis of their target delivery, which could also be achieved in the case of nonmetallic nanoparticles by surface characteristics that facilitate specific conjugate bonding. Dissolution potential of the nanoparticle, relative proportion of endocytosis and exocytosis, and characteristics of reaction environment are other factors that regulate the entry of nanoparticles in plants. Because nanoparticles of varying characteristics are able to enter the plant because of one or more factors enumerated in the preceding paragraph, they reflect both positive and negative effects on plant growth. However, the response of plants to nanomaterials varies with the type of plant species, their growth stages, and the nature of nanomaterials. Furthermore, the situation becomes more complex because of variation in the characteristics of the medium in which the plant grows, and even more so in soil. These effects stem from their potential to differentially influence a proportion of free radicals and plant hormones in addition to regulation of transmembrane transport. A positive effect on specific enzyme conjugate formation, nucleic acid synthesis coupled with improved carbon and nitrogen metabolism results in biomass accumulation, while enhanced oxidative stress and membrane damage induce ion leakage resulting in reduced growth. There are many gaps in our knowledge and there are many unresolved problems and new challenges concerning the biological effects of these nanoparticles. This, coupled with lack of proper legislation related to the use of nanomaterials, their confinement, and disposal, further aggravates the problem of ecotoxicity of nanoparticles. However, the development of nanomaterials that are biodegradable in soil and the environment, in addition to being less toxic, would be ideal for agricultural production. This chapter enumerates the details related to the response of plants to the exposure of nanoparticles, and clearly elucidates the intricacies of the different facets of their interaction at cellular, organ, and whole plant levels.

A large part of the more than 11 million tons of nanomaterials produced every year are metal and metal oxide nanoparticles (NPs), which ultimately end up in soil. NPs could enter into microbial cells either through endocytosis or by penetrating cells, and many of them, especially silver, copper, and zinc, have antimicrobial properties. Thus after entering the soil, NPs could adversely affect microorganisms present and disrupt essential functions of the soil. The effect of NPs on microorganisms and the mechanisms of their toxicity are comprehensively reviewed and discussed in this chapter. Both physical characteristics and chemical interactions of NPs at the nano–bio interface could elicit toxic effects, depending on their physical structure and chemical composition. Physical interactions, depending on size and surface properties of NPs at the nano–bio interface, could cause membrane disintegration and interference in transport processes. NPs, which are the same size as a protein molecule, interact with proteins and change their configuration, thus obstructing signaling processes in cells. Their shape can also affect toxicity by influencing uptake efficiency (rod-shaped NPs show maximum uptake and cubes minimum uptake), subsequently causing physical disintegration of membranes (truncated triangular silver nanoplates display the strongest biocidal action against Escherichia coli ). Once inside the cells, NPs affect the catalytic activity of enzymes and stability of protein structures. Release of metal ions and the generation of reactive oxygen species restrict normal physiological redox-regulated functions of cells and lead to oxidative modification of proteins, which causes mortality of cells. Carbon-based NPs are less toxic than metal or metal oxide NPs but generation of reactive oxygen remains a major mechanism behind their toxicity.

Experiments were carried out to study the effect of zinc oxide nanoparticles (nano-ZnO) on nitrogenase activity in legumes. In the first experiment, nodulated roots of cluster bean, moth bean, green gram and cowpea were dipped in Hoagland solution containing 1.5 and 10 μg mL−1 of nano-ZnO for 24 h. Nitrogenase activity in cluster bean, green gram and cowpea roots increased after dipping in solution containing 1.5 μg mL−1 nano-ZnO, but decreased in roots dipped in solution containing 10 μg mL−1 nano-ZnO. However, in moth bean roots, nitrogenase activity decreased after dipping in solution containing either concentration of nano-ZnO. In the second experiment, nodulated roots of green gram were dipped in Hoagland solution containing 1, 4, 6, 8 and 10 μg mL−1 nano-ZnO for 6–30 h before estimating nitrogenase activity. Results showed that an interactive effect of nano-ZnO concentration and exposure time influenced nitrogenase activity. The possible reasons behind this effect have been discussed. A model [A = 3.44 + 0.46t − 0.01t 2 − 0.002tc 2 (R 2 = 0.81)] involving linear and power components was developed to simulate the response of nitrogenase activity in green gram roots to the concentration and exposure time of nano-ZnO.

Plant water status and leaf gas exchange as influenced by micronutrients, kaolin and water management were studied to establish a relationship with fruit cracking in pomegranate in arid regions. Observations were recorded on fruiting pomegranate trees that were maintained under different water status and leaf gas exchange through mulching of tree basins and foliar spray of borax (0.4%), zinc sulphate (0.5%), kaolin (4.0%) with respect to fruit cracking, LWP, RWC, stomatal conductance, transpiration, photosynthetic rate and difference between ambient and leaf temperature of fruiting branch. The results showed that per cent fruit cracking was associated with reduction in leaf water potential, stomatal conductance and leaf transpiration. Such a situation coupled with high relative water content and photosynthetic rate as observed under combined sprays of borax (0.4%) + ZnSO4 (0.5%) and borax (0.4%) + ZnSO4 (0.5%)+ kaolin (4%) reflects the possible relationship of fruit cracking with selected physiological parameters. Plant water status also influences leaf gas exchange parameters and subsequently growth which may indirectly affect cracking in pomegranate fruits.