No abstract

Pre-emergence application of metribuzin stimulated the accumulation of nitrogen, especially in the form of protein. The application of metribuzin induced marked suppression of carbohydrates. The soluble sugars and polysaccharides in nontreated control plants declined throughout the experimental period. The inhibitory effect of metribuzin on carbohydrates was concomitant with changes in photosynthetic efficiency, biosynthesis of pigments (chlorophyll), and the nucleic acid contents. The chlorophyll a/b ratio was not affected by metribuzin application.

Foliar spray with the diluted PGPR (plant growth promoting rhizobacteria) cultures had utmost importance due to its content and release of stimulants, nutrients, antibiotics, biocides and siderofores. Potentiality of these microorganisms, in plant rhizosphere, in activation and improving of plant growth as will as increasing plant tolerance to different plant biotic and abiotic stresses have been proved. However, microbial types and even microbial strains varied for their potentiality to adapt, inhabit and release of stimulants and phytochemicals. A number of Azospirillum sp. isolates were isolated from phyllosphere of apple, orange, lemon, mango and guava trees, grown at El-Bostan area, Egypt. These isolates were used in spray of apple trees with the dose of 20 and 40 L/feddan compared to water spray control. Foliar spray of apple trees with all Azospirillum isolates notably induced the plant growth and increased fruit yield, but did not significantly affected fruit quality. However, the used isolates largely varied in their efficiency and potentiality. A3 isolate was the superior followed by A7 which attained the highest increases in shoot length, shoot diameter, leaf area, leaf dry weight leaf content of chlorophyll a, b and total chlorophyll as will as fruit yield over those of control treatment. But, the quality parameters, i. e., SSC (soluble solids content), acidity, firmness and color did not show consistent significant variations. The treatments of spray with Azospirillum isolates attained high increase in net return (L E/fed), the spray with the treatments of A7D (isolated from mango phyllosphere and used with the rate of 40 L/fed.) and A7R, which isolated from mango phyllosphere and used with the rate of 20L / fed.) were the superior treatments which achieved increases in net return over that of control (water spray) by 6120 and 6200 L E/fed respectively, followed by A3R (isolated from phyllosphere of apple and applied with 20 L/fed.) which gave 5595 L E/fed. It is noted that the microbial culture dose of 40 L/fed had no significant differences than the application of 20 L/fed. Therefore, we recommend the spray with an efficient Azospirillum isolate like A3 or A7 with the dose of 20 L/fed, and it is also of importance to condense studies on isolation and evaluation of these microorganisms to select the most efficient strains for use, as inoculants, in spray of apple trees.

Summary Glucose and fructose fed to radish slices were taken up at different relative rates with marked accumulation of carbohydrates; a possible working mechanism is presented to explain the differential rates of uptake. Addition of iodoacetate to the sugar media decreased both the uptake of sugars and the accumulation of carbohydrates. Although there was synthesis of proteins in the presence of iodoacetate, the synthesis both in iodoacetate and in iodoacetate plus sugar was less than in the absence of iodoacetate. Sugars and iodoacetate either alone or in combination increased the rates of CO2 output; a possible explanation of the different rates observed is given. Moreover, iodoacetate increased the permeability of the cell membranes as is evident from the increased leakage of nitrogen compounds from the tissues into the media.

Many synthetic biostimulants containing amino acids, macro-and microelements, humic acids and, sometimes, algae extracts have been used effectively for stimulating and increasing of fruit trees yield. The foliar spray with some PGPR (plant growth promoting rhizobacteria) has proved high potentiality in stimulating and increasing plant yield. The current study is concerned with the use of some PGPR types (Azospirillum brasilense, Pseudomonas fluorescens and Bacillis polymyxa) as an alternative to some commercial synthetic biostimulants i. e. Jisamar (J) and Furdos (F) in stimulating and improving yield of "Anna" apple trees.The study field of apple trees (eight years old) was chosen at El-Bostan area, El-Behira Governorate, Egypt. The trees were sprayed twice with the different stimulators, the first was at fruit set and the second was done after 30 days from fruit set. The control trees were sprayed with water.The microorganisms which were used for spray were counted in the plant phyllosphere and they showed heavy increase in the phyllosphere of the treated plants. The spray with the synthetic biostimulants showed remarkable improvement to the plant morphological characteristics, e. g. shoot length, shoot diameter, leaf area, leaf dry weight and leaf content of chlorophyll a, b and total chlorophyll. While, specific leaf weight (SLW) did not significantly change. Likewise, the spray with bacterial biostimulants proved similar potentiality as synthetic ones, and even, sometimes, surpassed them. The spray with Azospirillum brasilense gave the highest fruit yield; 45.1 and 41.2 kg/tree versus 33.5 and 32.0 kg/tree for control treatment in 2009 and 2010 seasons, respectively. The spray with Jisamar and Furdos gave 37.4 and 33.2 kg/tree and 36.5 and 34.7 kg/tree, respectively. The experimental treatments, raised the net return (£E/feddan) over that of control. Azospirillum brasilense spray attained the highest net return i. e. 21595 versus 16660, 16870 and 15650 £E/feddan for treatments of Jisamar, Fordose and control, respectively. Therefore, the substitution of synthetic biostimulant products with biological ones may be suitable for improving the plant growth, increasing productivity and raising the net return per feddan of Anna apple trees.