Plant Water Relationship: Concept, Importance of water, Water absorption mechanism

UPDATED ON:- 01-01-2024

पादप जल सम्बंध: अवधारणा, जल का महत्व, जल अवशोषण की क्रियाविधि (Plant Water Relationship: Concept, Importance of water, Water absorption mechanism):-

1. पादप जल सम्बंध की अवधारणा (Concept of Plant Water Relationship):-

·  पौधों का अधिकतर भार जल के कारण ही होता है।

(Most of the weight of plants is due to water.)

·  पादप कोशिकाओं में 70 – 75% तक जल होता है। जलीय पौधों की कोशिकाओं में 98% तक जल होता है।

(Plant cells contain 70 to 75% water. The cells of aquatic plants contain up to 98% water.)

·  पादपों में जल से संबन्धित निम्न कार्यिकीय क्रियाएँ होती हैं –

(The following physiological activities related to water take place in plants:-)

i. जल अवशोषण (Water Absorption)

ii. रसारोहण (Ascent of Sap)

iii. वाष्पोत्सर्जन (Transpiration)

2. जल का महत्व (Importance of water):-

·   जल कोशिकाद्रव्य का मुख्य घटक है। सभी जैव रासायनिक अभिक्रियाएं जलीय माध्यम में ही सम्पन्न होती हैं।

(Water is the main component of the cytoplasm. All biochemical reactions take place in aqueous medium.)

·   प्रकाश संश्लेषण की क्रिया में जल कच्चे माल के रूप में उपयोग होता है।

(Water is used as a raw material in the process of photosynthesis.)

·   जल एक सर्वोत्तम विलायक है। कोशिकाद्रव्य के विभिन्न घटक इसमें घुलनशील अवस्था में रहते हैं।

(Water is the best solvent. Various components of cytoplasm remain in soluble state in water.)

·   पौधों में गैसों का विसरण जलीय माध्यम से ही होता है।

(The diffusion of gases in plants occurs only through aqueous medium.)

·   मृदा से खनिज लवणों का अवशोषण जलीय माध्यम से ही होता है।

(The absorption of mineral salts from the soil occurs only through aqueous medium.)

·   पत्तियों में बने खाध्य पदार्थों का विभिन्न भागों में स्थानांतरण जल के माध्यम से ही होता है।

(The transfer of the food substances made in the leaves to different parts takes place only through water.)

·   विभिन्न प्रकार की पादप गतियाँ जल के कारण ही होती हैं।

(Various types of plant movements are due to water.)

·   जल पौधों के तापमान को सामान्य बनाए रखने में सहायक होता है।

(Water helps in maintaining normal temperature of plants.)

3. जल अवशोषण की क्रियाविधि (Water absorption mechanism):-

·   जल स्त्रोत (Water source):- पौधे मृदा से जल अवशोषित करते हैं। मृदा में उपस्थित केशिका जल को ही पौधों की जड़ें अवशोषित कर सकती हैं।

(Plants absorb water from the soil. Only the capillary water present in the soil can be absorbed by the roots of the plants.)

·   जल अवशोषण अंग (Water Absorption Organs):-

Ø  उच्च पादपों में जल मूल रोमों के माध्यम से अवशोषित किया जाता है। मूल के  मूल रोम क्षेत्र में लाखों की संख्या में एककोशिकीय मूल रोम पाये जाते हैं जो मृदा जल के सम्पर्क में रहते हैं।

(In higher plants water is absorbed through root hairs. Millions of unicellular root hairs are found in the root hair zone, which remain in contact with soil water.)

Ø  मूल रोमों की कोशिका भित्ति में पैक्टिन व सेलुलोज पाये जाते हैं जो जलस्नेही पदार्थ होते हैं। इसलिए इनकी कोशिका भित्ति जल के लिए पूर्णत: पारगम्य होती है।

(Pectin and cellulose are found in the cell wall of root hairs which are hydrophilic substances. Therefore, their cell wall is completely permeable for water.)

Ø  मूल रोम जल अवशोषण के लिए मूल के पृष्ठीय क्षेत्रफल को बढ़ा देते हैं।

(Root hairs increase the surface area of ​​the root for water absorption.)

·  अवशोषण की क्रियाविधि (Absorption mechanism):- जल अवशोषण की दो विधियाँ हैं –

(There are two methods of water absorption –)

1. सक्रिय जल अवशोषण (Active Water Absorption)

2. निष्क्रिय जल अवशोषण (Passive Water Absorption)

1. सक्रिय जल अवशोषण (Active Water Absorption):- जब जल अवशोषण की प्रक्रिया में मूल कोशिकाएं सक्रिय रूप से भाग लेती हैं तो इसे सक्रिय जल अवशोषण कहते हैं। यह तभी होता है जब मृदा में जल प्रयाप्त मात्रा में पाया जाता है। इसके सम्बंध में 2 मुख्य वाद हैं –

(When parent cells actively participate in the process of water absorption, it is called active water absorption. This occurs only when water is found in sufficient quantity in the soil. There are 2 main theories regarding this –)

a. परासरणिक वाद (Osmotic theory)

b. अपरासरणिक वाद (Non – osmotic theory)

a. परासरणिक वाद (Osmotic theory):-

Ø  मूल रोमों के धानी रस में खनिज लवण शर्करायें, कार्बनिक अम्ल आदि काफी अधिक मात्रा में घुले रहते हैं अर्थात इसकी सांद्रता अधिक होती हैं। जबकि इसके विपरीत मृदा विलयन की सांद्रता बहुत कम होती हैं। इस प्रकार मूल रोम के अन्दर परासरण दाब या DPD मृदा विलयन की तुलना में अधिक होता है।

(Mineral salts, sugars, organic acids, etc. are dissolved in large quantities in the vacuolar sap of root hairs, that is, its concentration is high. On the contrary, the concentration of soil solution is very less. Thus the osmotic pressure or DPD inside the root hair is higher than that of the soil solution.)

Ø  परासरण में जल हमेशा कम परासरण दाब या DPD वाले विलयन से अधिक परासरण दाब या DPD वाले विलयन की ओर गति करता है।

(In osmosis, water always moves from a solution with lower osmotic pressure or DPD to a solution with higher osmotic pressure or DPD.)

Ø  इस प्रकार जल परासरण के द्वरा मृदा विलयन से मूल रोम कोशिकाओं में प्रवेश करने लग जाता है।

(Thus water enters the root hair cells from the soil solution through osmosis.)

Ø  परासरण दाब प्रवणता या DPD प्रवणता (Osmotic Pressure Gradient or DPD Gradient):-

मृदा जल < मूल रोम < वल्कुट कोशिका < अंतश्चर्म कोशिका < परिरंभ कोशिका < जाइलम

(Soil water < root hair < cortex cell < endodermal cell < pericycle cell < xylem)

Ø  इस प्रकार जल कम परासरण दाब या DPD वाली कोशिकाओं से से अधिक परासरण दाब या DPD वाली कोशिकाओं की ओर गति करता हुआ अंत में मूल के जाइलम में पहुँच जाता है।

(Thus water moves from cells with low osmotic pressure or DPD to cells with high osmotic pressure or DPD, and finally reaches the root xylem.)

Ø  मूल दाब (Root Pressure):- जब अवशोषित जल मूल के जाइलम में पहुंचता है तो यहाँ एक दाब विकसित होता है जो जल को जाइलम में कुछ ऊंचाई तक ले जाता है। इसे मूल दाब कहते हैं।

(When the absorbed water reaches the root xylem, a pressure develops here which lift the water up to some height in the xylem. This is called the root pressure.)

b. अपरासरणिक वाद (Non – osmotic theory):-

Ø  यह वाद थिमन (1951) व क्रेमर (1959) के द्वारा प्रस्तुत किया गया था।

[This theory was given by Thiman (1951) and Kramer (1959).]

Ø  इस वाद के अनुसार जल अवशोषण अधिक परासरण दाब या DPD वाले विलयन से कम परासरण दाब या DPD वाले विलयन की ओर होता है।

(According to this theory, water absorption occurs from a solution with high osmotic pressure or DPD to a solution with low osmotic pressure or DPD.)

Ø  इसके लिए ऊर्जा की आवश्यकता होती है जो मूल कोशिकाओं के श्वसन से प्राप्त होती है।

(This requires energy which is obtained from the respiration of root cells.)

Ø  प्रमाण (Evidences):-

i. श्वसन को रोकने वाले कारक जल अवशोषण की दर को कम कर देते हैं।

(Factors that inhibit respiration reduce the rate of water absorption.)

ii. विष जो मूल कोशिकाओं की मेटाबोलिक क्रियाओं को रोकता है, जल अवशोषण की दर को कम कर देता है।

(The toxin that inhibits the metabolic activities of root cells, also reduces the rate of water absorption.)

iii. Auxin एक वृद्धि हार्मोन है जो कोशिकाओं की मेटाबोलिक क्रियाओं को बढ़ा देते हैं, जल अवशोषण की दर को भी बढ़ता है।

(Auxin is a growth hormone that increases the metabolic activity of cells, also increasing the rate of water absorption.)

2. निष्क्रिय जल अवशोषण (Passive Water Absorption):- जब जल अवशोषण की प्रक्रिया में मूल कोशिकाएं निष्क्रिय बनी रहती हैं तो इसे निष्क्रिय जल अवशोषण कहते हैं। यह तभी होता है जब मृदा में जल प्रयाप्त मात्रा में उपस्थित नहीं होता है।

(When the root cells does not participate in the process of water absorption, it is called passive water absorption. It occurs only when water is not present in sufficient amount in the soil.)

Ø  यह वाष्पोत्सर्जन की दर उच्च होने के कारण होता है।

(This occurs due to the high rate of transpiration.)

Ø  जल का तीव्र वाष्पीकरण पर्ण के जाइलम में एक खिंचाव उत्पन्न कर देता है। यह खिंचाव पर्ण के जाइलम से शुरू होकर नीचे की ओर तने के जाइलम से होता हुआ मूल के जाइलम में पहुँच जाता है।

(The rapid evaporation of water causes a suction tension in the xylem of the leaf. This suction tension starts from the xylem of the leaf and goes down through the xylem of the stem and reaches the xylem of the root.)

Ø  मूल के जाइलम से यह खिंचाव मृदा जल तक पहुँच जाता है।

(This suction tension from the root xylem reaches the soil water.)

Ø  इसके फलस्वरूप जल मृदा विलयन से निकलकर मूल रोम से होता हुआ मूल के जाइलम में पहुँच जाता है। यहाँ से तने के जाइलम में होता हुआ पर्ण के जाइलम में पहुँच जाता है।

(As a result, water left the soil solution through the root hair and reaches the root xylem. From here it passes through the xylem of the stem and reaches the xylem of the leaf.)

4. जल का मार्ग (Path of Water):- जल अवशोषण के दो मार्ग होते हैं –

(There are two routes of water absorption -)

i. Apoplast:- जब अवशोषित जल कोशिका भित्ति व अंतराकोशिकीय अवकाशों से होकर आगे बढ़ता है। इसमें जल कोशिका के अंदर कोशिकाद्रव्य में प्रवेश नहीं करता है।

(When absorbed water moves through the cell wall and inter-cellular spaces. In this route, water does not enter the cytoplasm inside the cell.)

ii. Symplast:- जब अवशोषित जल प्लाज्मा झिल्ली व प्लाज्मोडेस्माटा से होकर आगे बढ़ता है। इसमें जल कोशिका के अंदर कोशिकाद्रव्य में प्रवेश करता है।

(When absorbed water moves through plasma membrane and plasmodesmata. In this route, water enters the cytoplasm inside the cell.)

5. महत्वपूर्ण शब्द (Important terms):-

·   मृदा जल (Soil Water):- यह 4 प्रकार का होता है –

(It is of 4 types –)

i. क्लेदन जल (Hygroscopic Water)

ii. केशिका जल (Capillary Water)

iii. गुरुत्वीय जल (Gravitational Water)

iv. संयुक्त जल (Combined Water)

·   क्षेत्र धारिता (Field Capacity):- किसी भी मृदा में गुरुत्वीय जल को छोड़कर उपस्थित शेष जल को क्षेत्र धारिता कहते हैं।

(The water present in the soil except the gravitational water is called field capacity.)

·   जल धारण क्षमता (Water Holding Capacity):- मृदा में गुरुत्वाकर्षण बल के विपरीत केशिकाओं में रह जाने वाले जल की प्रतिशत मात्रा को जल धारण क्षमता कहते हैं।

(The percent amount of water that remains in the capillaries against the gravitational force in the soil is called water holding capacity.)

·   स्थायी मुरझान बिन्दु (Permanent Wilting Point):- पादप की स्थायी मुरझान के प्रथम लक्षण के समय मृदा में जल की प्रतिशत मात्रा को स्थायी मुरझान बिन्दु कहते हैं।

(The percent amount of water present in the soil at the time of the appearance of first sign of permanent wilting of the plant is called permanent wilting point.)

6. सक्रिय व निष्क्रिय जल अवशोषण में अन्तर (Difference between Active and Passive Water Absorption):-