The osmotic concentration (osmotic potential) of onion leaf sap did not adjust to chloride salinity, and consequently water potential, turgor, stomatal aperture and transpiration were reduced. Although osmotic concentration of bean and cotton leaf sap did adjust to a saline root medium and turgor was no less in the salinized plants than in the controls, stomata of the salinized plants remained only partly open and transpiration was reduced. Net photosynthesis of onion plants was reduced by salinity (this effect being much enhanced in a hot dry atmosphere) but it could be rapidly raised to the level of the controls by inducing elevated leaf turgor. Stomatal closure was initially responsible for most of the ∼30 % reduction in photosynthesis of salinized beans. This was due to interference with CO2 diffusion and could be overcome by raising the CO2 concentration in the air. At a later stage of growth, salinity affected the light reaction of bean photosynthesis, and elevation of the air CO2 had little effect. Closure of stomata of salinized cotton plants had only a relatively small effect on net photosynthesis. Light intensity and CO2 concentration experiments showed that salinity was reducing the photosynthesis of cotton leaves mainly by affecting the light reaction of photosynthesis. It is concluded that chloride salinity does affect the water balance and rate of photosynthesis of plants and that the nature and degree of the effects will depend upon climatic conditions and may be very different between plant species and in the same species at different periods of growth.

bonate ion & oxygen level as related to chlorosis.

No abstract

Seedlings of Petunia hybrida cv. Snow Cloud were subjected to root zone temperatures at the bottom surface of the pots of 15.6° to 19.4°C (NT) or 21° to 35° (HT) and photoperiods of 9 (SD) or 13 hr (LD) for 25 days in a eontrolled-environment chamber with air temperatures of 21° for 9 hr and 15.6° for 15 hr. HT × LD plants produced the largest total leaf area, largest main stem leaves, and most dry weight of all treatments; they were tallest and bloomed first, but had the fewest lateral branches. HT × SD plants developed the most lateral branches at the fastest rate and had a total leaf area, dry weight gain, and root development comparable to those of the LD treatments. NT × SD plants were the smallest. Crop productivity efficiency was determined to be NT × SD = 2.9%, HT × SD = 3.4%, NT × LD = 3.7%, and HT × LD = 3.9%.

Crop productivity efficiencies (CPE) of around 8% (the ratio of the dry weight gain of the crop to the potential to produce dry weight), were realized with petunias (Petunia hybrida Villm.), provided that the crop canopy was essentially closed at the beginning of the 9- to 12-day experimental periods and that there were many branches (sinks). This was found at either long or short photoperiods or at either a normal (15.6°C) or reduced (7.2°) temperature for the 16-hour night periods. Long photoperiods resulted in significantly increased CPE through increased size of the leaves before the crop canopy was closed. Elevated root temperature increased CPE after a sizeable number of lateral branches had formed.