Drought is one of the most important abiotic stress factors limiting maize production worldwide. The objective of this study was to investigate whether photoprotection of PSII was associated with the ...degree of drought tolerance and yield in three maize hybrids (30Y87, 31R88, P3939). To do this, three maize hybrids were subjected to three cycles of drought, and we measured the activities of photosystem II (PSII) and photosystem I (PSI). In a second field experiment, three maize hybrids were subjected to drought by withholding irrigation, and plant water status, yield and yield attributes were measured. Drought stress decreased leaf water potential (Ψ
) in three maize hybrids, and this reduction was more pronounced in hybrid P3939 (-40%) compared to that of 30Y87 (-30%). Yield and yield attributes of three maize hybrids were adversely affected by drought. The number of kernels and 100-kernel weight was the highest in maize hybrid 30Y87 (-56%, -6%), whereas these were lowest in hybrid P3939 (-88%, -23%). Drought stress reduced the quantum yield of PSII Y(II), photochemical quenching (qP), electron transport rate through PSII ETR(II) and NPQ, except in P3939. Among the components of NPQ, drought increased the Y(NPQ) with concomitant decrease in Y(NO) only in P3939, whereas Y(NO) increased in drought-stressed plants of hybrid 30Y87 and 31R88. However, an increase in cyclic electron flow (CEF) around PSI and Y(NPQ) in P3939 might have protected the photosynthetic machinery but it did not translate in yield. However, drought-stressed plants of 30Y87 might have sufficiently downregulated PSII to match the energy consumption in downstream biochemical processes. Thus, changes in PSII and PSI activity and development of NPQ through CEF are physiological mechanisms to protect the photosynthetic apparatus, but an appropriate balance between these physiological processes is required, without which plant productivity may decline.
Pests are major factor affecting the crop yield, quality, and esthetic value. Although pest resistance is genetically controlled, it is mediated through physiological and biochemical processes ...interrelated with the nutritional status of the plant. Nutrition of plant may determine its resistance or susceptibility to pests. An experiment was conducted to determine whether and up to what extent varying concentrations of N modulate the infesting rate of whitefly on Okra (
Hibiscus esculentus
). Twenty-one-day-old okra plants were subjected to five concentrations of 4, 8, 12, 16, and 20 mM N for 30 days. Number of eggs, nymph were counted on each plant after every 4 days. Growth and yield of okra plants increased with increasing supply of N but it decreased slightly at the highest level of N (20 mM). Leaf soluble proteins, amino acids, and soluble sugars were determined on fresh weight basis. From these results, it is clear that increasing N level increased the biosynthesis or accumulation of protein, free amino acid, and sugars that might have attracted more whitefly for feeding.
The wastewater of a tannery in Multan, Pakistan, was alkaline with high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) values along with much higher concentrations of total settle ...able salts and suspended solids, sodium adsorption ratio and high amount of sodium having the water quality class C sub(3)S sub(1). Effluent was examined for its chemical constituents and the effect of its various dilutions was examined in greenhouse on two newly recommended sunflower cultivars (FH-330 and FH-245) during their whole growth period. Percentage of germination, chlorophyll, carbohydrates and protein contents of both the sunflower cultivars showed significant (p = 0.05) decreasing trend with increasing effluent concentrations. Vegetative growth parameters like plant height and number of leaves per plant were significantly (p = 0.05) reduced with the increasing levels of effluents. Rate of leaf senescence of both cultivars was higher under higher effluent concentrations. Yield of sunflower crop in both cultivars was significantly (p = 0.05) reduced due to effluent concentrations. Seeds per capitulum were decreased to 49%, seeds weight per plant to 61 - 66% and 100-seed weight to 49 - 59%. The appearance of pale yellowish color of the affected plants was due to reduction in photosynthetic material under higher effluent concentration. Full strength effluent concentration caused the reduction in biomass accumulation and reproductive growth of sunflower cultivars. The results revealed that cultivar FH-330 was relatively resistant to varying effluent concentrations as compared to the cultivar FH-245. However, the tannery effluents due to the presence of chemicals are not suitable for inclusion in irrigation system.
Oxalis corniculata as a successful lawn weed: A study of morphological variation from contrasting habitats Malik, M.I. (Bahauddin Zakariya Univ., Multan (Pakistan). Inst. of Pure and Applied Biology); Mahmood, S. (Bahauddin Zakariya Univ., Multan (Pakistan). Inst. of Pure and Applied Biology); Yasin, G. (Bahauddin Zakariya Univ., Multan (Pakistan). Inst. of Pure and Applied Biology) ...
Pakistan journal of botany,
(Mar 2012), Letnik:
44, Številka:
1
Journal Article
Recenzirano
Oxalis corniculata, an abnoxious weed and is of cosmopolitan distribution. The species is a successful invader and seems to be adapted to a wide array of habitats. In the present study various ...survival strategies of the species under different environmental conditions were assessed through the variability of morphological character expressions. Eight populations of the O. corniculta were sampled from 4 contrasting habitats and were studied for various traits. The populations exhibited distinct morphological responses with respect to changing environmental conditions. The variability of phenotypic expressions seems to provide some selective advantage for survival under contrasting habitat situations. The species appeared to be a successful lawn weed as the maximum adaptive significance of character expressions was observed from a mowed lawn. The study suggested that various abiotic/ biotic factors did not limit the growth of the species. Hence, chemical control seems to be an appropriate strategy for weed management.
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