The interaction between P fertilization of citrus and the mycorrhizal fungus Glomus fasciculatus was examined in a greenhouse study. A low fertility loamy sand (4.6 ppm P) was provided with all necessary soil nutrients except P. This soil received superphosphate [Ca(H2PO4)2 · H2O] at rates of 0, 6, 28, 56, 278, and 556 ppm of P. Seven replicate mycorrhizal and nonmycorrhizal Brazilian sour orange and Troyer citrange seedlings were grown at each P fertility level. After 5 months, mycorrhizal sour orange which received 0 fertilizer P were similar in size to non‐mycorrhizal sour orange which were fertilized with 278 ppm P. Mycorrhizal citrange which received 0 fertilizer P were similar in size to nonmycorrhizal citrange which were fertilized with 56 ppm P. Dry weights of mycorrhizal sour orange seedlings were significantly greater than nonmycorrhizal sour orange seedlings when fertilized with 0, 6, 28, and 56 ppm P (947, 1089, 347, and 253% greater, respectively). Dry weights of mycorrhizal citrange seedlings were significantly greater than nonmycorrhizal citrange seedlings only when fertilized with 0 and 6 ppm P (746 and 300% greater, respectively). The %P in leaves of both citrus cultivars was enhanced by the mycorrhizal association at all P fertility levels. Variation in absorption of K, Mg, and Na by the citrus cultivars appeared to be primarily influenced by P concentrations of the seedlings. Variation in absorption of Zn, Cu, and Mn appeared to be influenced by both P concentrations of the seedlings and the presence of the mycorrhizal fungus. The number of G. fasciculatus spores/cm3 of soil which were associated with inoculated plants decreased with increasing P fertility levels. With mycorrhizal sour orange, numbers of spores decreased from 10.1 spores/cm3 soil at 56 ppm P soil to 0 spores/cm3 soil with plants at 556 ppm P. With mycorrhizal citrange, numbers of spores decreased from 5.7 spores/cm3 soil at 28 ppm P to 0 spores/cm3 soil at 56 ppm P. No correlation was found between soil P or % P in leaves, roots or stems of seedlings and the elimination of spore production.

In a greenhouse experiment the mycorrhizal fungus, Glomus fasciculatus, significantly increased growth of Troyer citrange (Poncirus trifoliata L.) (TC) seedlings in 20 of 26 methylbromide‐fumigated citrus soils from southern California. Of the six soils in which G. fasciculatus provided no growth increase, two were greenhouse soils, three were nursery soils, and only one was a field soil. Glomus fasciculatus increased foliar P, K, and Cu concentrations and decreased foliar Mg and Na concentrations of TC grown in the majority of the 26 citrus soils. Foliar concentrations of P, K, Ca, Na, Zn, Mn, Cu, and Fe from either mycorrhizal or nonmycorrhizal TC could not be significantly correlated with the mycorrhizal dependency of TC in the soils studied. A positive correlation was observed between foliage concentrations of Mg in nonmycorrhizal TC and mycorrhizal dependency. Mycorrhizal dependency of TC was also positively correlated with soil pH and inversely correlated with extractable soil P (bicarbonate), Zn, Mn, Cu, percent organic matter, and cation exchange capacity. In the fumigated soils studied, it was highly probable that inoculations with G. fasciculatus would induce significant growth response in TC provided the soils had <34 ppm extractable P, 27 ppm extractable Mn, 12 ppm extractable Zn, or 3% organic matter. The magnitude of the mycorrhizal dependencies of TC on G. fasciculatus in the 26 citrus soils were accurately predicted with equations which used soil P, Mn, Zn, and also Cu and pH as independent variables.

KEY WORDSAmino acids Cowpea Proteins Water stress SUMMARY This study was undertaken to evaluate water stress effects during vegetative, flowering, and podfilling stages ofcowpea plants ( Vigna unguiculata L.) grown under natural field conditions in southern California on seed yield and protein and free amino acid content of the cowpea seeds.The lowest concentration of N was found in the seeds of the control treatment plants while the seed yield from these treatments was the highest as compared with the N concentration and yield of seeds from plants subjected to water stress during flowering and podfilling stages. The concentration of N in the seeds was inversely related to the seed dry weight yield.Protein arginine, -threonine, -serine, -cystine, -valine, -methionine, and -isoleucine were significantly affected by water stress at the three growth stages. There was no consistent pattern in the effect of water stress on the individual amino acids. The sum of protein amino acids in the cowpea seeds was not significantly influenced by the various treatments since some of the protein amino acids increased and others decreased producing an averaging effect on the figures comprising the sums of the amino acids.Water stress during the flowering and pod-filling stages increased the free amino acid pool, and at the same time, inhibited incorporation of the amino acids into the protein chain-thus lowering the protein amino acid fraction simultaneously.With the exception of methionine plus cystine, the essential amino acids in the seeds were present at concentrations equal to or greater than recommended by the World Health Organization and FAO. It is of particular importance to note that the concentration oflysine in the cowpeas was substantially higher than that found in wheat grain. It is also important to note that the amount of essential amino acids per gram of protein was not measurably affected by the water stress treatments during any of the growth stages.

Jojoba (Simmondsia chinensis), a woody shrub, produces seeds which have several potential uses. The objectives of this experiment were to study the effects of soil temperature and soil oxygen supply on the nutrient uptake of the jojoba plant. Presently, there is little information on effect of soil physical factors on plant nutrients. The study was conducted in a greenhouse with constant temperature tanks to maintain root temperatures at 21, 27, and 33 C. Soil oxygen supply to the roots was controlled by controlling the concentration of oxygen in the atmosphere above the soil columns. Plants grown at a 33 C soil temperature produced significantly more dry weight than plants at 21 or 27 C. Concentrations of N, P, K, Na, Mn, and Fe in the leaves of plants grown at 33 C were substantially higher than leaves grown at 21 or 27 C. In general, nutrient concentrations in roots and total amount in plants were higher in plants grown at 33 C than at 21 or 27 C. The two lowest levels of soil oxygen supply to the roots (1.5 and 6.5%) significantly reduced dry weight of leaves, stems, and roots compared to plants grown at oxygen levels of 12 and 21%. Decreased soil oxygen significantly reduced the concentration of K, Ca, Mg, Zn, Mn, and B in leaves while concentrations of N, Na, and Fe were increased. Concentrations of N, P, K, Mg, Na, B, and Fe in roots grown under low soil oxygen were less than plants grown with 21% oxygen. Low levels of soil oxygen significantly increased concentration of Na in leaves and stems and decreased the concentration in the roots. This study indicates that growth and nutrient uptake of jojoba is best at higher temperatures in well‐aerated soils.

Several factors associated with senescence of the rind of the Navel orange fruit and their response to GA were studied from the time of color change, green to orange, until the fruit passed the point of any commercial value. This period is typified by a doubling in the concentration of sugar, a decrease in glucose respiration, and increase in the ratio of K/Ca+Mg . No seasonal trend could be assigned to Oz uptake, protein N, total N, or P, Zn, Cu, B, or Na. GA treatment at the time of color change did not seem to affect these factors until the rind approached senescence. At this point, GA effects were observable in the form of higher rates of Oz uptake, higher rate of glucose respiration, a lag in sugar accumulation, a lower K/Ca+Mg ratio, and a higher level of P. These results were interpreted as indicating that GA maintained a more functional mitochondrial membrane and plasmalemma membrane.The imminence of senescence in many plant organs is marked by the loss of green color and appearance of anthocyanins or carotenoids. This change is sufficiently dependable so that comparative measures of chlorophyll content are often used to plot the approach of senescence. The fruit of Citrus sinensis, cultivar, Navel orange approach senescence with the typical decrease in chlorophyll content, synthesis and accumulation of carotenoids, as well as softening and general weakening of the rind. Gibberellin A3 (GA), which has often been associated with the hastening of senescence (1, 2), appears to delay senescence in the rind of the Navel orange. GA-treated fruit exhibit a delayed chlorophyll loss (3), slower carotenoid accumulation (4), delayed softening of the rind, and diminished accumulation of rind exudate (5) . (This latter condition should not be confused with the exudate resulting from an aphid infestation.)To gain a better understanding of the changes accompanying senescence in the Navel orange rind and the probable manner in which GA acts in delay-