Polyethylene Glycol Induced Water Stress Effect on Apple Seedlings. II. 45Calcium Uptake1

Abstract

Polyethylene glycol (PEG)-induced water stress in nutrient solutions decreased both water consumption and 45Ca uptake by apple seedlings (Malus domestica Borkh.) The decrease in water uptake was more severe than the decrease in 45Ca uptake. When 45Ca uptake was calculated on the basis of water consumption, it was found that 45Ca uptake was not dependent on water uptake although water was necessary for movement of 45Ca. In split-root experiments, PEG and 45Ca were either applied to the same half of the root or to separate halves. Calcium uptake decreased in plants subjected to water stress. The results indicated that the site of this decrease was at the root, not the aerial portion of the plant which, indirectly, may affect root function and thus 45Ca uptake. Split-root experiments also indicated that the unstressed half of the root cannot fully compensate for the stressed half of the root in either water or 45Ca uptake. Water use of plants with half of their root under a −5.0 bar water stress was decreased by 30%. Urea-nitrogen pretreatment did not modify the effect of osmotic stress on leaf Ca, Mg and K concentrations, water use or dry matter production during the period of applied water stress. All these parameters decreased with increasing solution osmotic stress.

Physiological and Nutritive Effects of K-Pretreatment and KCl Sprays on Water-stressed and Unstressed Apple Seedlings1

“…1). Similar responses to PEG-induced water stress at -1.0 bar were observed in previous studies (4,16). There was also a significant K-pretreatment x PEG x day interaction on apple seedlings' water consumption rate (Table 3).…”

“…The apple seedlings used in that experiment can be considered here as high-K plants. The above data indicate that PEG-induced water stress decreased the ab sorption capacity of the roots (4,16,17,18), and this effect can be noted in as short a period of time as 2 weeks. Clark (2) reported that an osmotic water stress ( -1 .0 bar) decreased N, P, and Rb concentrations in wheat within 24 hr.…”

Effects of PEG-induced Water Stress on Calcium Uptake in Peach Seedlings

“…An 11-mm-diameter circle was cut with a cork borer from the youngest fully expanded leaf of each plant. The radioactivity of the fresh stem and leaf sections was determined by counting in a Nuclear-Chicago planchet counter according to procedures described previously (7). This counting method was acceptable, despite the self-absorption of some ra dioactivity by the sample tissue, because equal amounts of tissue were used and only relative radioactivity of the samples was needed.…”

“…Mason (12) found that seedlings of apple grown in soil which was allowed to dry until the plants wilted had much less total Ca than seedlings grown at field capacity. Uptake of 45Ca by apple seedlings in nutrient solution was reduced when solution osmotic potential was lowered (7).…”

Overexpression of PeNAC122 gene promotes wood formation and tolerance to osmotic stress in poplars

“…One group was used as control, with poplars grown in a normal nutrient solution (1/2 Hoagland), whereas the other group was treated with a nutrient solution (1/2 Hoagland) containing 20% PEG6000 for 7 days. Physiological and biochemical indexes of three mature leaves at the same position were analyzed, and total RNA was extracted from the fifth leaf at the top of each poplar (Gergely et al, 1980). The lower epidermis of leaves under osmotic stress and control treatments was peeled off with scotch tape, then photographed under an optical microscope to measure the ratio of stomatal length and width (Gao et al, 2020).…”