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Abstract
The present study was carried out during two consecutive seasons of 2001 and 2002 in a greenhouse belonging to El-kanater Horticulture Research Station, Kalyobia Governorate, Egypt.
Uniform and Healthy two year old transplants of two rootstocks namely: MM 106 and Pyrus communis were the plant material used in this study, on February 1st during both seasons plastic pots of 35 cm. diameter that had been filled with about 10 kg from each soils under study ( clay; calcareous and sandy brought from Qaloub, Wady El-Mulak and Belbies , respectivelly). Soil types were taken from a depth of 0-30 cm; from ground surface. Soils were chemically and mechanically analyzed before period of equilibration. Irrigation was carried out twice weekly by adding one liter tap water per each pot until, investigated treatments of this study was started in both experimental seasons. whereas irrigation with different investigated saline solutions was start during both seasons of study.
Saline solutions were prepared for irrigation at the concentration of tap water (0), 2000, 4000 and 6000 ppm of NaCl, Na2SO4, CaCl2, MgSO4, KCl and K2SO4 as well as each concentration was prepared with two levels of sodium adsorption ratios (S.A.R.) i.e., 3 and 6 and each level of sodium adsorption ratio have two Cl: SO4 levels i.e., (low and high). To avoid salts accumulation irrigation with tap water was applied every 21 days, then followed by rewatering with the same salt solution the next day.
It was aimed to investigate the salt tolerance of MM 106 and Pyrus communis rootstocks by irrigation with saline solution of different concentrations; SAR and Cl:SO4 under 3 soil types.
Thus two factorial experiment were conducted, an experiment was devoted for each rootstock. The complete randomized block design with three replications, was employed whereas each was represented by 2 plants (grown individually in 35.0 cm. diameter plastic pots).
Fourty eight treatments represented the different possible combinations between four investigated factors namely; a) 3 soil kinds ( clay ; calcareous and sandy) ; b) saline concentration (2000; 4000 and 6000 ppm); c) SAR (3 & 6) and d) Cl: SO4 ratios (low & high), beside irrigation with tap water as control were investigated.
Specific and interaction effects of the investigated factors and their combinations were studied through the response of the following measurements:
V-I. Growth measurements:
Average length of (stem and root); stem diameter number of leaves per plant; leaf & total assimilation area; fresh and dry weights of various transplants organs (stem, leaves, roots and total plant) and top/root ratio were the investigated growth measurements in both experiments.
V-II. Some physiological properties:
Leaf relative turgidity (L.R.T), leaf succulence grade (L.S.G.), leaf osmotic pressure (O.P.) in bar and leaf water potential (L.W.P.) in response to investigated treatments were estimated.
V-III. Chemical analysis:
In this regard, foliar photosynthetic pigments (chlorophyll a & b); stem total charabohydrates; proline contents and nutritional status (Leaf, N, P, K, Ca, Mg, Fe, Mn , Zn and Na contents) in response to the included treatments of two experiments were investigated.
V-IV. Leaf anatomical structure:
In this regard some leaf anatomical characteristics i.e, cutical & epidermal thickness of both upper and lower leaf blade surface; palisade & spongy tissues thickness and number of xylem rows in vascular bundle were investigated regarding their response to saline stress.
Data obtained during both experimental seasons 2001 and 2002 could be summarized as follows:
V-I. Growth measurements:
In this regard the investigated fifteenth growth parameters namely: plant height; stem diameter; number of leaves per plant; average area of individual (leaf & total assimilation area per plant); fresh & dry weights of various plant organs (leaves; stem ; root and total plant) and top/root ratio in response to specific effect of four studied factors i.e., soil kind; salt concentrations, sodium adsorption ratio and chloride levels (Cl: SO4 ratio) as well as interaction effects of their possible combinations were investigated during both 2001 and 2002 experimental seasons.
A. Specific effect:
1. Regarding the specific effect of soil kind, data obtained during both seasons revealed that, M.M.106 and Pyrus communis rootstocks transplants grown in clay soil was the superior descendingly followed by calcareous soil and sandy soil. Such trend was true in most cases pertaining the 15 investigated growth measurements during two seasons.
2. As for the specific effect of salt concentrations, results also declared a significant decrease in plant height; root lengths; stem diameter average area of either individual leaf or total assimilation area /plant and fresh & dry weights of plant organs (leaves, shoots, roots and total plant) all being progressively depressed by all the used salinity concentrations, but the depressive effect was more pronounced with the highest salts concentration except top/root ratio where the reverse was true during two seasons of study.
3. Results also declared a significant decrease in all the previously mentioned vegetative growth parameters with increasing sodium adsorption ratio (SAR) from 3 to 6 except top/root ratio which followed the opposite trend during the 2001 and 2002 experimental seasons.
4. With respect to the specific effect of chloride level (Cl: SO4 ratio), data obtained displayed that increasing chloride levels (Cl: SO4 ratio) in irrigation water resulted in an obvious reduction of all investigated growth measurements during the two seasons of study.
B. Interaction effect:
1. Data obtained revealed that specific effect of each investigated factor was directly reflected on its own combinations. Herein, the M.M.106 and Pyrus communis rootstocks transplants grown in clay soil irrigated with 2000 ppm X SAR 3 X lower chloride level (Cl: SO4 ratio) exhibited statistically the least reduction in values of various vegetative growth parameters follow the tap water irrigated ones as compared to the analogous rates of other saline combinations during two seasons of study.
2. On the contrary, the least values of the investigated vegetative growth measurements were always in concomitant to those M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil X highest salt concentration (6000 ppm) X SAR 6 X higher Cl: SO4 ratio whereas, the severest decrease was detected during the two seasons of study. However, other combinations were in between the aforesaid 2 extremes.
V.II. Some physiological properties of leaf:
Leaf water potential (L.W.P); leaf osmotic pressure (L.O.P); leaf relative turgidity (L.R.T) and leaf succulence grade (L.S.G.) in response to soil kind; salt concentration; SAR and chloride levels (Cl: SO4 ratio), as well as their combinations were the investigated leaf physiological properties.
A. Specific effect:
1. Regarding the specific effect of soil kind, data obtained revealed that the highest values of leaf water potential and leaf relative turgidity were always in concomitant to M.M.106 and Pyrus communis rootstocks transplants grown in clay soil while the reverse was true with M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil. M.M.106 and Pyrus communis rootstocks transplants grown in clay soil had leaves with the lowest values of osmotic pressure and leaf succulence grade. Differences were significant with the former aforesaid four physiological leaf characteristics. In addition, M.M.106 and Pyrus communis rootstocks transplants grown in calcareous soil was intermediate as compared to two other soil kinds under study regarding the response of all investigated leaf physiological properties.
2. Concerning the specific effect of salt concentration, obtained results revealed that the lowest values of (L.W.P.) and (L.R.T.); were significantly exhibited by 6000 ppm salt concentration in irrigation water. On the contrary, increasing salt concentration in irrigation water, increased significantly values of both leaf osmotic pressure and leaf succulence grade during two seasons of study.
3. Results also declared a significant decrease in leaf water potential (L.W.P.) and leaf relative turgidity (L.R.T.) with increasing both sodium adsorption ratio and chloride level in irrigation water, while the trend took the other way around with both leaf osmotic pressure (L.O.P.) and leaf succulence grade as the specific effect of both SAR and Cl:SO4 ratio were concerned took the other way around during two seasons of study.
B. Interaction effect:
1. Data obtained regarding the interaction effect of (soil kind X salt concentration X SAR X chloride levels) pointed out that the highest values of leaf water potential (L.W.P.) and leaf relative turgidity (L.R.T.) were statistically in concomitant to M.M.106 and Pyrus communis rootstocks transplants grown in clay soil irrigated with either tap water or 2000 ppm saline solution of SAR 3 and lower Cl: SO4 ratio. However the least value was coupled with irrigated transplants with 6000 ppm saline solution of SAR 6 and higher Cl: SO4 ratio during the study. Other combinations were in between regarding the response of the aforesaid 2 leaf physiological properties.
2. On the other hand, the interaction effect between the four investigated factors i.e., soil kind; salinity concentration; SAR and Cl: SO4 ratio in the irrigation water caused a noticeable variances. Herein, the highest values of both leaf osmotic pressure and leaf succulence grade (L.S.G.) detected by M.M.106 and Pyrus communis rootstocks transplants irrigated with 6000 ppm saline solution of SAR6 and higher Cl: SO4 ratio regardless of soil kind, especially with osmotic pressure. However the least values of both osmotic pressure and leaf succulence grade were completed with irrigated transplants of two rootstocks with either fresh water or saline solution of 2000 ppm concentration and lower ratio of SAR and Cl: SO4 ratio, regardless of soil kind. In addition, other combinations were in between regarding the response of such investigated leaf physiological properties.
V.III. Chemical composition:
V.III. 1. Photosynthetic pigments (foliar pigments);
Data obtained regarding leaf photosynthetic pigments contents (Chlorophyll A; B and carotenoids compounds) of M.M.106 and Pyrus communis as influenced by the specific and interaction effects of soil kind; salt concentration; SAR and chloride levels (Cl: SO4 ratio), as well as their possible combinations, data obtained revealed the following:
A. Specific effect:
1. M.M.106 and Pyrus communis rootstocks transplants grown in clay soil were statistically the richest followed in a descending order by M.M.106 and Pyrus communis rootstocks transplants grown in calcareous and sandy soils, where Pyrus communis M.M.106 rootstocks transplants grown in sandy soil was the poorest.
2. The obtained results revealed that leaf photosynthetic pigments i.e., Chlorophyll A & B and carotenoids, all progressively decreased by raising salinity concentrations during two seasons of study.
3. Increasing level of either sodium adsorption ratio (SAR) or Cl: SO4 ratio in irrigation water significantly decreased leaf chlorophyll A, B and carotenoids compounds during the study.
B. Interaction effect:
1. The interaction effect of various combinations between soil kind; salinity levels; sodium adsorption ratio and chloride level (Cl: SO4 ratio) was obviously detected. Herein, irrigated M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil with 6000 ppm saline solution of SAR 6 and higher Cl: SO4 exhibited statistically the greatest rate of redution in their leaf chlorophyll A, B and carotenoids. However the least decrease was in leaves of M.M.106 and Pyrus communis rootstocks transplants grown in clay soil and irrigated with 2000 ppm saline solution of SAR6 and lower Cl: SO4 ratio. In addition, other combinations were in between the aforesaid 2 extremes.
V.III. 2. Shoots total carbohydrates contents:
1. Data obtained during both seasons revealed that stem total carbohydrates content of M.M.106 and Pyrus communis rootstocks respond specifically to the 4 investigated factors. Hence, M.M.106 and Pyrus communis rootstocks transplants grown in clay soil was statistically the richest followed in descending order by M.M.106 and Pyrus communis rootstocks transplants grown in calcareous and sandy soils during two seasons of study.
2. Shoots total carbohydrates respond to either salt concentration; sodium adsorption ratio (SAR) or chloride levels (Cl: SO4 ratio). Hence, rising any of salinity concentration; and ratio of either SAR or Cl: SO4 resulted in decreasing shoot total carbohydrates content.
B. Interaction effect:
Obtained results revealed that total carbohydrates respond obviously to interaction effect of four investigated factors. Herein, the lowest total carbohydrates from one hand was always in concomitant to the M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil and irrigated with 6000 ppm salinized water of SAR 6 and higher Cl: SO4 ratio. The reverse (highest total carbohydrate levels) was markedly coupled with M.M.106 and Pyrus communis rootstocks transplants grown in clay soil and irrigated with tap water followed by those irrigated with 2000 ppm saline solution of SAR 3 and lower Cl: SO4 ratio during two seasons of study in addition other combination were in between the aforesaid to extremes with variable tendency of variance as members (combinations) of such intermediate category were compared each other during both seasons of study.
V.III. 3. Effect on leaf proline contents:
A. Specific effect:
1. Data obtained displayed that proline contents respond specifically to each of the four investigated factors (soil kind; salt concentration; SAR and Cl: SO4 ratio), were transplants of both rootstocks followed the same trend. M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil had statistically the richest leaves followed in a descending order by M.M.106 and Pyrus communis rootstocks transplants grown in calcareous and clay soils, where the later was the inferior in this concern.
2. The obtained results revealed that, proline contents being progressively increased with salinity concentrations.
3. Results also declared a significantly increase in proline contents with increasing either SAR or chloride levels (Cl: SO4 ratio) during two seasons of study.
B. Interaction effect:
The interaction effect of combinations between the four investigated factors i.e., soil kind; salinity concentration; SAR and Cl: SO4 ratio, data obtained revealed that the highest value of proline contents were found by M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil X highest salinity concentration (6000 ppm) X SAR 6 X higher Cl: SO4 ratio while the reverse was detected by the tap water irrigated combinations followed in an increasing order by those representative of M.M.106 and Pyrus communis rootstocks transplants grown in clay soil X lowest salinity concentration (2000 ppm ) X SAR 3 X lower Cl: SO4 ratio.
V.III. 4. Leaf mineral composition:
Data obtained during both seasons regarding the leaf N, P, K, Ca, Mg, Fe, Mn , Zn and Na contents of M.M.106 and Pyrus communis rootstocks transplants in response to specific and interaction effects of soil kind; salt concentration; SAR and chloride level (Cl: SO4 ratio) and their possible combinations could be summarized as follows:
A- Specific effect:
1- Referring the specific effect of soil hind, data obtained during both season revealed that M.M.106 and Pyrus communis rootstocks transplants grown in clay soil exceeded statistically the tow other soils (calcareous and sandy) regarding their leaves N, P, K, Mg and Zn contents. However, M.M.106 and Pyrus communis rootstocks transplants grown in clay soil had the least Ca, Fe, Mn and Na levels. However, M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil leaves had the highest level of Ca, Fe, Mn and Na that associated with the least values of N, P, K, Mg and Zn contents. Meanwhile, M.M.106 and Pyrus communis rootstocks transplants grown in calcareous soil in most cases was intermediate as compared to two other soil kinds in this concern.
2- As for the specific effect of salt concentrations, the leaves N, P, K, Mg, Fe, Mn and Zn contents decreased significantly and gradually with increasing salt concentration in irrigation water, while the reverse was found with leaf Ca and Na contents during two seasons of study.
3- Increasing either sodium adsorption ratio (SAR) from 3 to 6 and /or chloride level (CL: So4 ratio) in irrigation water significantly decreased leaf N, P, K, Mg, Fe, Mn and Zn contents, while the reverse was true with leaf Ca and Na contents, where raising either SAR or Cl: SO4 ratio increased them significantly during two seasons of study.
B- Interaction effect:
Regarding the interaction effect of various combinations between four investigated factors (soil kind; salt concentration; sodium adsorption ratio and Cl: So4 ratio), data obtained during 2001 & 2002 experimental seasons revealed that specific effect of each investigated factor was directly reflected on its own combinations. Herein, the irrigated M.M.106 and Pyrus communis rootstocks transplants grown in sandy soil irrigated with the highest concentrated saline solution (6000 ppm) of higher SAR (6) and Cl: SO4 ratio had the richest leaves in their Ca and Na contents associated with the least levels of N, P, K, Mg, Fe, Mn and Zn. The trend took the other way around with control (continuously irrigated transplants with tap water) followed by those supplied with 2000 ppm saline solution of lower SAR (3) and lower Cl: SO4 ratio where the least values of leaf Ca and Na contents with the higher N, P, K, Mg, Fe, Mn and Zn contents were recorded especially M.M.106 and Pyrus communis rootstocks transplants grown in clay soil.
V. IV. Leaf anatomical structure:
Leaf anatomical structure of two rootstocks transplants (M. M.106 and Pyrus communis)) as influenced by salt stress (irrigated with 2000; 4000 and 6000 ppm) saline solution were investigated. Obtained results revealed that salinity increased thickness of both cuticle and epidermis layers of two leaf surfaces as well as palisade tissue thickness. However, spongy tissue thickness and xylem rows in vascular bundle were decreased in salt stressed transplants of two rootstocks as compared to the analogous ones of tap water irrigated ones (control).
from obtained results of the present dissertation it could be recommended for nursery men that under shortage of available fresh water that saline solution of relatively lower level of salt concentration (2000 ppm); SAR 3 and Cl: SO4 could be safely used for irrigation purposes of nursery transplants under any soil kind clay, calcareous and sandy soils conditions .