PHYSIOLOGICAL STUDIES IN SOME HALOPHYTIC DESERT GRASSES OF CHOLISTAN

The experiment for the evaluation of 26-accessions of Cholistan desert grasses belonging to four grass species viz., panicum antidotale, Cellchrus ciliaris, sporobohus iocladus and Lasiurus Sindicus against drought, salinity and combined drought and salinity, was conducted both in the laboratory and net house under the controlled environment at NIAB, Faisalabad and in the field conditions of Cholistan desert area, Bhawalpur. A germination experiment was conducted in petriplates to study the germination percentage and seedling growth against three levels of salinity i.e. 15, 25 and 35 dS m-1. Accessions of Lasiurus Sindicus could not germinate under Faisalabad environmental conditions (Details are given in 'Discussion'). Accession LS 3/6 (Sporobolus iocladus), Local-2, Local-8, KS 1/2 (Cenchrus ciliaris) and KS 1/1 (Panicum antidotale) performed better upto 25 dS m-1 salinity levels while at 35 dS m-1, a significant reduction was observed in all accessions. Similarly, these 26-grass accessions were also studied for four screening techniques like germination stress tolerance index (GSI), plant height and dry matter stress tolerance indices (PHSI, DMSI) and cell membrane stability (% injury) under saline conditions (15, 25 and 35 dS m-1) and relative water relations (relative saturation deficits, RSD) for screening the grasses against\ud \ud Studies (CHIDS), Islamia University, Bahawalpur. The different morphological attributes (plant height, plant fresh weight, plant dry weight, above ground biomass), physiological attributes (photosynthetic flag leaf area, transpiration rate, leaf diffusive resistance), biochemical attributes (amino acids, proline, proteins, carbohydrates, nitrate reductase activity), macro nutrients (nitrogen, phosphorus, potassium, calcium) and micro nutrients (sodium, chloride, boron, iron) were studied at NIAB while only some morphological and biochemical parameters were studied at CHIDS due to non-availability of HI- Tech Lab facility at CHIOS.\ud \ud Under drought conditions at NIAB, different accessions showed different performance for all the characters studied. Morphological attributes were adversely affected by drought stress. The accession LS 3/6 (S. iocladus) for plant height, BJ 1/2 (P. antidote ale) and KS 1/2 (C. ciliaris) for plant fresh and dry matter yield and accessions KS 1/1, KS 1/2 and LS 3/6 showed better results as compared to other grass accessions. Flag leaf area and transpiration rate decreased while leaf diffusive resistance increased under drought stress. The accessions Local-4 and LS 3/6 showed better performance for flag leaf area however, Local-14 performed poorly under highest drought conditions (25% F. C). In accession LS 3/6, transpiration rate was least affected at light soil moisture deficit. This accession also tolerate drought, because leaf diffusive resistance was less as compared to other accessions. Accession RD 1/1 of P. antidotale also performed better regarding physiological changes in response to water stress. Total free amino acids accumulation increased with water deficit and was higher in accessions Local-8 of C. ciliaris, LS 3/6 of S. iocladus at 25% F.C. Prolines, Proteins and carbohydrates accumulation was also higher in plants subjected to drought stress. Highest praline contents were recorded in accession Local-14 and KH 1/6 in T2 (25% F.C) while minimum in LS 3/6. Same accessions revealed highest accumulation of proteins. Carbohydrates were higher in accession KS 1/1 at T1 and in Local-13 at T2 Nitrate reductase activity decreased with the increase in drought stress in all accessions, however, accession KS 1/2 performed poor regarding nitrate reductase activity and accessions KS 1/1 and LS 3/6 performed better at both drought levels. Soil moisture deficit conditions also influenced the macro and micro-elements in grasses. Nitrogen, potassium, calcium, sodium and chloride contents increased while phosphorus, boron and iron decreased under soil water deficit environment. The highest increase in nitrogen was observed in accession Local-14 and Local-16 at T2 while maximum decrease (46.54%) in phosphorus was recorded in accession KS 1/2. Under 25% F.C (T2), accession KS 1/2 superpassed the others by accumulating more potassium ions (2-times as compared to control). Highest accumulation of calcium (2.56 and 6-times over control) was recorded in accession Local-10 at T1 and T2 respectively. At highest drought level, sodium was maximum in accession Local-14 and chloride was maximum in Local-15. Minimum reduction in boron and iron contents was recorded in accessions RD 1/1 and LS 3/6.\ud \ud The same trend of increase or decrease in morphological, physiological, biochemical and nutrient uptake was observed in all grass accessions under saline conditions except potassium and calcium which increased under drought but decreased accumulation were more than 50% in all accessions except KH 1/6 and KS 1/1. Highest proline concentration (7-times) was observed in accession RD 1/1 while maximum proteins were recorded in accession Local-16 at all salinity treatments. Highest accumulation of carbohydrates was also observed in RD 1/1, LS 3/6 and KS 1/2 at highest salinity level (25 dS m-l). Nitrate reductase activity decreased with the increase in salinity: At 25 dS m-l, reduction in nitrate reductase activity was more than 50%. Nitrogen contents were least affected at all salinity levels in accession RD 1/1. Phosphorus reduction reached upto 28.69% in accession Local-14 at highest salinity level. Potassium contents also decreased more than 50% in accessions belonging to Cenchrus ciliaris . Calcium contents were also reduced with increase in salinity. Highest increase in sodium at all salinity levels was observed in accession Local-14 while that of chloride ill accession Local-8. In all grass accessions boron and iron decreased with increase in salinity.\ud \ud Combined drought and salinity stress also adversely affected the performance of grasses. The trends of decrease or increase in different attributes were same as that observed in drought and salinity conditions. The accessions performing better under drought and salinity experiments also performed better under combined drought and salinity.\ud \ud Under field conditions, accessions RD 1/2 of P. antidotale and LS 3/6 of S. iocladus performed better than others while accessions of Lasiurus Sindicus showed poor performance.\ud \ud It can be concluded that three types of stresses caused a significant influence on germination, morphology, physiology, biochemical changes and nutrient uptake of different grass accessions, depending upon the environmental conditions, plant growth pattern, plant life cycle and grass species. However, relationship between different attributes can be drawn as by correlation analysis