The investigation was aimed to establish the effect of salinity on the physiology and growth of Eucalyptus camaldulensis (Dehn.) and to evaluate the effect of Abscisic acid, on the growth of Eucalyptus and uptake and accumulation of ions under salt (NaC1) and drought stress. Different provenances of Eucalyptus camaldulensis were selected on the basis of their growth performances under saline condition.
The seeds of different provenances of Eucalyptus camaldulensis were obtained from University of Agriculture, Faisalabad (Provenance I), Punjab Forest Research Institute, Faisalabad (Provenance II), Biosaline Research Station-I, Lahore (Provenance III) and Biosaline Research Station-II, Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad, (Provenance 1V).
During the first experiment, seed germination and % survival were studied for four selected provenances of Eucalyptus camaldulensis on the basis of their tolerance to salt. At 1.5% NaC1, the provenance II and III performed better than provenances I & IV.
Second experiment was conducted to study the growth, uptake and accumulation of ions in the above mentioned four provenances of Eucalyptus camaldulensis. Salt treatments were given to three months old seedlings in pots. The leaves of plants were harvested 30 days after treatment for determining the uptake and accumulation of ions. The results indicated that Na+ accumulation was increased in all the provenances with increase in salt both in shoot and root. However, in provenance II and III much higher concentration of Na+ were retained in root. The accumulation of K+ was decreased with the increase in NaC1 concentration. Provenance II maintained higher concentration of K+ while provenance I and IV had the minimum. The maximum Ca ++ concentration was found in provenance II and provenance III both in shoot and the root.
Transpiration was decreased by ABA, salt and drought but the combined effect of ABA with salt and drought was more inhibitory. The stomatal resistance of third leaf was significantly higher due to ABA, drought and salt, but the ABA addition further augmented the stimulatory effect on stomatal resistance.
The water use efficiency (WUE) was greater in ABA and drought treatments made alone and in combination but salt decreased the water use efficiency and ABA was unable to overcome this decrease in combined treatment.
The N concentration was decreased with the increase in NaC1 treatments, both in shoot and root. Similarly, P was also minimum at 2% NaC1 in root of all the provenances but provenance I maintained highest P concentration.
The K/Na ratio was decreased with the increase in salt both in shoot and root in all the provenances. The K/Na ratio in all the provenances were similar in case of shoot while in case of root, K/Na ratio was higher in provenance II and III.
Third experiment comprised evaluation of the effect of abscisic acid (ABA) on growth, physiological and biochemical parameters and ion uptake of Eucalyptus camaldulensis under induced salt, drought and combined stress of salt and drought. The three month old seedling were treated with ABA alone or ABA+ salt, ABA + drought and ABA + drought + salt.
The root fresh weight and shoot fresh and dry weight was higher than control under salt treatment and ABA maintained that, but ABA alone was inhibitory.
ABA alone or in combination with drought appeared to decrease the Na content of shoot and root; the magnitude of inhibition was greater in shoot. Salt treatment increased the Na accumulation both in root and shoot and ABA application was inhibitory.
Both proline and betaine accumulation was highest in provenance II and III while it was minimum in provenance IV. The interaction between provenance x treatment was also significant. The highest accumulation of proline and betaine was obtained by T10 (salt + ABA at 60% Field Capacity).
Both salt treatment and ABA decreased the Ca+Mg content in shoot and more so in root. The inhibitory effect of ABA was more marked in combined treatment with salt and drought. The N (%) in shoot was increased due to ABA treatment as well as salt treatment but the % increase was more due to ABA. Water use efficiency (WUE) was significantly increased with ABA but drought and salt treatments showed decrease in WUE in all the provenances. Stomatal resistance was increased under both drought and salt stresses. Provenances I and IV had less stomatal resistance and provenances II and III had higher stomatal resistance. Provenances II and III showed decrease in transpiration in response to salt stress.
It was concluded that ABA analogues could be used to combat drought and salinity stress in the field. The K/Na ratio in roots may be taken as an index for selection of salt tolerance in Eucalyptus. This trait may be combined with the production/ accumulation of osmoregulants.