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Flashcards in lecture 5 Plant water requirement Deck (43)
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For every gram of organic matter produced, how much water is absorbed?

Water plays a critical role in the life of the plants. For every gram of organic matter produced by a plant, 500 g of water is absorbed by the roots and subsequently transpired through leaves.


What happens if there is a slight imbalance in water flow?

A slight imbalance in water flow can cause water deficits and malfunctioning in cellular processes. Thus every plant must maintain balance in its uptake and loss of water


What is important for nutrients uptake from soil?

The stream of water taken up by the roots is a step important for nutrients uptake from soil.


What is the most limiting factor for agricultural productivity?

Of all the resources that plants need to grow and function, water is the most limiting factor for agricultural productivity.


what does water availability limit?

Water availability limits the productivity of natural ecosystems. Therefore, a better understanding of the uptake and loss of water by plants is very important.


The environmental condition when water deficits constraints agricultural production, is characterized as?



What is the major difference between plant and animal cells that affects their relation with water?

is the existence of cell wall in plants.


Cell wall allows plant cells to build up?

internal hydrostatic pressure, called turgor pressure which is essential for many physiological processes.


The physiological processes include?

cell enlargement, gas exchange in the leaves, transport in the phloem, and across membranes.


In growing plant tissues, water constitutes what % of mass?

water constitutes 80% - 95% of the mass.


Many biochemical reactions of cell occur in the presence of?

water and it directly participates in many chemical processes.


Why do plants evaporate water?

Plants continuously absorb and lose water. Plants evaporate water from the leaf to absorb CO2 needed for photosynthesis. Such water loss is called transpiration.


What mechanisms are included in the transport of water from the soil to the plant body?

diffusion, bulk flow and osmosis.


What happens in simple diffusion?

substances move down a concentration gradient


What happens in pressure-driven bulk flow?

substances move down a pressure gradient


What happens in osmosis?

both type of gradients influence transport.


How is the direction and rate of water flow across a membrane dtermined?

not solely by the concentration gradient of water or by the pressure gradient, but by the sum of both driving forces.


What are the major factors influencing the water potential in plants?

concentration, pressure, and gravity.


What is strongly influenced by water potential and its components?

Cell growth, photosynthesis and crop productivity


The plant water relations can be represented by a?

simple thermodynamic equation which relates to water potential.


In which direction does water always move down its water potential gradient?

from areas of higher water potential to areas of lower water potential


How is water potential typically measured?

Water potential is typically measured as the amount of pressure needed to stop the movement of water. The unit used to express this pressure is the megapascal (MPa).


What happens when solutes are added to water?

the potential becomes negative


What is main site for evaporative water loss (transpiration)?

Leaves are the main site of evaporative water loss (transpiration)


Why do leaves show different degrees of structural adaptation?

to minimise water, loss, while allowing photosynthesis


Adaptation can be extreme in?

hydrophytes and xerophytes


A smaller range of features is shown in?



What are hydrophytes?

aquatic plants (e.g. Water Lily)


What are hygrophytes?

inhabit damp environments (e.g. ferns).


What are Mesophytes?

go in well-aerated soils with good water availability but exposed to drying air (e.g. wheat)