S. H. Lips

Carbohydrate metabolism in leaves and assimilate partitioning in fruits of tomato (Lycopersicon esculentum L.) as affected by salinity

Abstract Salinity improve tomato fruit quality by enhancing hexose accumulation. To study the involvement of the carbohydrate influx into fruits under saline conditions, we have studied carbohydrate metabolism in leaves and the partitioning of photosynthetic 14 C in fruits of tomato plants exposed to 0, 50, or 100 mM NaCl. Carbohydrate content and the activity of ADP-Glc-PPase (EC 2.7.7.27) in the fruits were also determined at different stages of fruit development. Photosynthesis rates per unit leaf area were only slightly affected by moderate salinity (50 mM NaCl) while causing a considerable inhibition of leaf area expansion. Sucrose concentration was higher in leaves of plants exposed to NaCl than in non-saline controls, correlating with the enhanced activity of sucrose phosphate synthase (EC 2.3.1.14) and with the low activity of acid invertase (EC 3.2.1.26). Salinity enhanced the transport of 14 C-assimilates from the pulse leaf to adjacent fruits and the diversion of 14 C label to the starch fraction of the fruit. It also prolonged the period of starch accumulation in developing fruits. The immature fruit from salinity-treated plants showed significant higher activity of ADP-Glc-PPase with approximately twofold higher starch content than in controls. It is concluded that, under saline conditions, both a higher concentration of sucrose in the leaves and a faster rate of starch synthesis in the immature fruit may constitute part of a mechanism responsible for a higher sugar content in the mature fruit.

Physiological aspects of ammonium and nitrate fertilization

Abstract Various physiological effects of ammonium, nitrate and mixed ammonium‐nitrate nutrition of plants have been studied in this laboratory during the last years. Some of the characteristic distinctions observed between plants growing on these nitrogen sources are described and discussed. Biomass production of ammonium‐grown plants increased with K+ concentration in the nutrient medium between 0.1 to 3 mM , while nitrate‐fed plants reached maximal growth around 0.25 mM K+ . The water use efficiency (WUE) of ammonium‐fed plants was lower and also more dependent on K+ than that of plants receiving nitrate. At low K+ levels (0.1 mM) in the medium, plants growing on ammonium‐N spent nearly twice as much water through transpiration per unit mass than nitrate‐fed plants. WUE of plants receiving NH4NO3 was poor at low K+ (similar to ammonium‐fed plants) but at high K+ this plants grew even better than nitrate‐grown plants. Overall transpiration per plant was little affected by K+ levels in the medium. Conseq...

Salinity and nitrogen nutrition studies on peanut and cotton plants

Abstract The effect of the nitrogen form (NH4 + or NO3 ‐) added to the nutrient solution and salinity levels (NaCl) was studied in peanut and cotton plants grown in hydroponics. Salinity levels particularly affected the growth of NH4 +‐fed plants. Salinity and nitrogen form had different effects in the levels of K+ and Na+ in the shoots of these two species. Salinity only reduced photosynthesis in severely stressed cotton plants. A high correlation was observed between the level of K+ and stomatal conductance. Ammonium resulted in a less efficient use of nitrogen under saline conditions for both species.

Wheat growth as affected by nitrogen type, pH and salinity. I. biomass production and mineral composition

Abstract The interactions among the form of N supplied (ammonium or nitrate), NaCl concentration, and pH of the nutrient solution were studied on wheat (Triticum aestivum L. cv. Barkai) grown hydroponically. Plant growth was affected by increasing NaCl concentration from 0 to 100 mM. Increasing the pH from 5 to 8 resulted in reduced growth of ammonium‐fed plants, but not of nitrate‐fed plants, at all concentrations of NaCl applied. Potassium concentration in the shoot was inversely correlated with Na, but directly correlated with shoot dry weight. These correlations were affected, however, by the form of N in the nutrient media. The sensitivity of ammonium‐fed plants to NaCl may be due mainly to the decreased concentration of K in the shoot.

Physiological studies on salinity and nitrogen interaction in alfalfa. I. Biomass production and root development

Abstract The effects of the interaction between salinity, nitrogen (N) forms and concentration were studied with alfalfa (Medicago sativa L.) grown in pots with fine sand under greenhouse conditions. Increased salinity (0–100 mM NaCl) substantialy reduced the dry weight of roots and shoots, relative growth rate (RGR) of the plant, relative multiplication rate of root, mean extension rate of root, number of root branches, and root length. Additional N considerably moderated the salinity effects on these parameters. The promotive effect of nitrate‐N was more pronounced on shoot and root dry weight and root lengths while number of root tips relatively increased more by ammonium‐N on all salinity levels. Moreover, salinity affected root length per plant relatively more than number of root tips per plant. The plants were relatively tolerant at the second harvest to salinity and N levels. It is suggested that exogenous supply of N as nitrate would improve the vegetative growth of alfalfa by moderating the suppr...

Potassium, nitrogen, ammonium/nitrate ratio, and sodium chloride effects on wheat growth: I. Shoot and root growth and mineral composition

Abstract Fertigation with KNO3 as a means of reducing salinity hazards was tested with peanut (Arachis hypogaea) plants grown on dune sand, resulting in a reduction of plant growth and yield. The objective of this work was to study the interactions between N, K+ and NaCl as well as the effects of the NH4 +/NO3 ‐ ratio on vegetative and reproductive growth. Wheat (Triticum aestivum L.) plants were grown in polyethylene pots with fine calcareous dune sand with different proportions of NH4 + and NO3 ‐, under saline (60 mM NaCl) and non‐saline conditions. Three replicates were harvested at the beginning of flowering, and one was grown to grain maturity. NaCl reduced shoot dry weight in all the treatments. Increasing the NH4 + proportion in the total of 6 mM N in the nutrient solution, increased shoot dry weight, did not change nitrogen concentration in the dry mass but increased P percentage, either with or without 60 mM NaCl. The number of tillers produced in each treatment was correlated with dry matter yie...

Wheat growth as affected by nitrogen type, pH and salinity. II. photosynthesis and transpiration

Abstract The interactions among the form of N (ammonium or nitrate) supplied, NaCl concentration and pH of the nutrient media were studied with wheat (Triticum aestivum L. cv. Barkai) plants growing hydroponically. The effects of these parameters on mineral content and plant growth were reported in our previous paper (1). Neither photosynthetic or transpiration rates were affected by salinity in the range of NaCl concentrations used. Stomatal conductance, however, decreased with increasing NaCl concentrations in the medium. Chlorophyll content of the leaves of ammonium‐fed plants decreased with increasing pH. This response is more moderate in nitrate‐grown plants. Consequently, a difference is observed between photosynthesis rates expressed on the basis of leaf area or of chlorophyll content. The relative content of K and Na, and its possible effect on photosynthesis and transpiration are discussed.

Physiological studies on salinity and nitrogen interaction in alfalfa. II. Photosynthesis and transpiration

Abstract The interaction between salinity and nitrogen (N) forms and concentration was studied with alfalfa (Medicago sativa L.) grown in pots with fine sand under greenhouse conditions. Salinity (0–100 mM NaCl) caused a substantial reduction in carbon assimilation rate, stomatal conductance, water use efficiency, and leaf area, while transpiration rate was least affected. Salinity effects were considerably moderated by additional N supply, varied with form, concentration, and stage of plant growth. The photosynthesis was reduced more in ammonium‐ than in nitrate‐fed plants, while the transpiration rate was relatively lower in nitrate‐fed plants grown either with or without NaCl. The plants also responded differently to salinity and N levels at two harvests. This indicated a change in plant behaviour with age. The promotive effect of N on photosynthesis and other parameters in saline as well as in non‐saline conditions may be attributed to the enhanced synthesis and availability of carbon assimilatory enz...

Comparison of growth of flacca and wild-type tomato grown under conditions diminishing their differences in stomatal control

Abstract The effects of endogenous and exogenous abscisic acid (ABA) on the growth of flacca , a specific ABA-deficient mutant of tomato ( Lycopersicon esculentum ), and the wild-type variety Rheinlands Ruhm (RR) were investigated under conditions in which the effects of stomatal behavior on growth were minimized. Two experimental systems were used: (1) germination experiments in which the root and hypocotyl lengths were compared and (2) shoot tip culture of in vitro experiments. Flacca had shorter roots and longer hypocotyls than RR and the fresh biomass of plantlets developed from flacca shoot tip culture was greater than that of wild-type plantlets. Low exogenous ABA significantly improved fresh biomass of both plantlets while high exogenous ABA significantly inhibited their growth. It was concluded that endogenous ABA improves root growth and inhibits shoot growth in young tomato seedlings. A low concentration of exogenous ABA tends to improve plant growth while high level of exogenous ABA inhibits plant growth.

Potassium, nitrogen, ammonium/nitrate ratio, and sodium chloride effects on wheat growth. II : Tillering and grain yield

The objectives of this project were to study the interactions among N, K + and NaCl and the NH 4 + /NO 3 − ratio and their effect on vegetative and reproductive growth of wheat (Triticum aestivum L.). Plants were grown in polyethylene pots with fine calcareous dune sand with and without 60 mM NaCl, two nitrogen concentrations (2 or 6 mM), two K + concentrations (0.5 or 5 mM) and four NH 4 + /NO 3 − ratios (0:1, 1:1, 3:1 and 1:0). Three replicates were harvested at the beginning of flowering, and one grown to grain maturity. Shoot and root growth, and mineral composition of the leaves, were reported in part I of this series (1) (...)