The effect of irrigation and crop load on stem water potential and apple fruit size

Summary

The effect of irrigation rate under various crop loads on the fruit size of apple (Malus domestica Borkh cv. Golden Delicious) was investigated in three field experiments in 1993–1995. During the first two years the field experiments evaluated the effects of various crop loads on yield, fruit size and midday stem water potential under 40% deficit irrigation. In 1995, the effects of five irrigation levels (0.42–1.06 of USDA Class A evaporation pan) and four crop loads (100–450 fruits per tree) were studied in a factorial experiment. Midday stem water potential increased with irrigation level and decreased with crop load in 1993 and at the lowest irrigation level in 1995. Daily fruit growth rate decreased with midday stem water potential in 1993 and at the lowest irrigation level in 1993. The effect of crop load on fruit growth rate was associated with limited soil water availability. A reduction in yield and average fruit size were associated with midday stem water potentials lower than –1.3 MPa. Taking an additional 0.1 MPa as a safety factor, –1.2 MPa could serve as a reasonable threshold for irrigation control in the orchard.     

Resistance among accessions of the generalycopersicon andsolanum to four of the main insect pests of tomato in Israel

Laboratory, greenhouse and field experiments were conducted to identify plant accessions of the genusLycopersicon and ofSolarium pennellii resistant toSpodoptera littoralis (Boisd.),Plusia chalcites (Esp.),Heliothis armigera (Hbn.), andPhthorimaea operculella (Zeu.), four insect pests of the cultivated tomato. Percent survival, larval weight, duration of development, damage scores, etc., were the criteria used to determine the relative resistance of the examined accessions. TheL. hirsutum accession LA 1777 and theL. hirsutum f.glabratum accession LA 407 were found to be highly resistant to all four insect pests. TheS. pennellii accession LA 716 was found to be resistant to the first three insects, but only partially resistant toP. operculella. The possible mechanisms of resistance,i.e., the physical entrapment of larvae and the toxic action of phytochemicals in the various accessions, are discussed.     

Direct synthesis of amides from alcohols and amines with liberation of H2

Given the widespread importance of amides in biochemical and chemical systems, an efficient synthesis that avoids wasteful use of stoichiometric coupling reagents or corrosive acidic and basic media is highly desirable. We report a reaction in which primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen (the only products) in high yields and high turnover numbers. This reaction is catalyzed by a ruthenium complex based on a dearomatized PNN-type ligand [where PNN is 2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine], and no base or acid promoters are required. Use of primary diamines in the reaction leads to bis-amides, whereas with a mixed primary-secondary amine substrate, chemoselective acylation of the primary amine group takes place. The proposed mechanism involves dehydrogenation of hemiaminal intermediates formed by the reaction of an aldehyde intermediate with the amine.