找到一些有趣的对仙人掌的描述： About cacti
Most plants get rid of litres of water every day, by a process called transpiration, giving out water through their leaves (a bit like when we sweat!). Cactus leaves have become a lot smaller so they don't lose so much water; most have shrunk to spines or hairs but some have disappeared altogether!
The stems are green to make food for the plant, because the leaves can't do it any more - they are too small. Cacti stems and ridges expand to store lots of water when it rains. Think of a camel that stores food in his hump! This guides as much rain as possible to the roots. Some cacti and succulents have swollen roots that store up water for the days when it doesn't rain; sometimes in the desert it doesn't rain for months
Leaf succulents
Leaf succulents store water in their leaves. Their leaves can take different forms as a means of protection from drying out. They can be:
hairy or waxy
covered in a white 'bloom'
silvery-grey in colour
Many of these plants wait until it rains to flower. Rain also makes their seeds germinate and these seeds can stay dormant for a long time in the soil.
Interesting facts
The giant saguaro cactus is:
The tallest cactus in the world, growing up to 20m (67ft) high.
It can weigh up to six tonnes, which is mainly the weight of the stored water.
Some of these cacti are 250 years old.
The Gila woodpecker nests inside the stem of the saguaro cactus where the temperature inside can be up to 30ºC (86ºF) cooler than outside.
The prickly pear cactus has a big network of shallow roots, which can quickly soak up lots of water when it rains.
The ocotillo plant only grows leaves after it has rained - as soon as the soil dries out, they all drop off.
Some cacti spines are nearly 15cm (6in) long. Boerhavia repens is a desert plant which can germinate, grow, produce flowers and ripen seeds in the space of ten days after it has rained.
The century plant takes 25 years to grow a flower. Then it dies. Lots of agaves do this!
Pebble plants (Lithops species) only have two leaves, and they look like the pebbles on the ground next to the plant. Their beautiful flower grows between the leaves.
Some species of agave plants (succulents not cacti) are also called Needle and Thread plants because the spiny tip and stringy leaf margin can be broken off and used to sew - and are even strong enough to sew through leather.
The spines of the Barrel cactus were used by local people for fishing hooks.
Desert wild flowers. These flowers bloom after a rain, then die within a matter of days. That is the example of this life.
查了下water plant 的特征：
Characteristics
Characteristics of aquatic plants:
A thin cuticle. Thick cuticles reduce water loss; thus most hydrophytes have no need for thick cuticles.
Stomata that are open most of the time, because water is abundant and there is no need for it to be retained in the plant. This means that guard cells on the stomata are generally inactive.
An increased number of stomata, which can be on either side of the leaves.
A less rigid structure: water pressure supports them.
Smaller roots: water can travel directly into leaves through osmosis; thus large root systems are not required for water uptake.
Feathery roots: no need to support the plant.
Specialized roots able to take in oxygen.
For example, some species of buttercup (genus Ranunculus) float slightly submerged in water; only the flowers extend above the water. Their leaves and roots are long and thin and almost hair-like; this helps spread the mass of the plant over a wide area, making it more buoyant. Long roots and thin leaves also provide a greater surface area for uptake of mineralsolutes and oxygen.
Wide flat leaves in water lilies (family Nymphaeaceae) help distribute weight over a large area, thus helping them float near surface.
Many fish keepers keep aquatic plants in their tanks to control phytoplankton and moss by removing metabolites.
Many species of aquatic plant are invasive species. Aquatic plants make particularly good weeds because they reproduce vegetatively from fragments.
Sundews are a genus of carnivorous plants which usually live in wet habitats where the acidic conditions limit the amount of nutrients they can extract from the soil. These plants therefore supplement their diet by catching and digesting small creatures such as insects. Some species of sundew are very long-lived. Sundews can be found growing on every continent except Antarctica.
炎热干旱的沙漠里面也有花么？在前面宝宝们知道了植物的生长需要水，沙漠里面缺乏的是水，植物们是如何各项神通来获得水分的呢。
这一章可以稍微衍生一下，先让宝宝发挥一下想象力，植物如何利用有限的水分来生长的。
最容易的例子就是总所周知的仙人掌了。
找到一些有趣的对仙人掌的描述：
About cacti
Most plants get rid of litres of water every day, by a process called transpiration, giving out water through their leaves (a bit like when we sweat!). Cactus leaves have become a lot smaller so they don't lose so much water; most have shrunk to spines or hairs but some have disappeared altogether!
The stems are green to make food for the plant, because the leaves can't do it any more - they are too small.
Leaf succulents
Leaf succulents store water in their leaves. Their leaves can take different forms as a means of protection from drying out. They can be:
- hairy or waxy
- covered in a white 'bloom'
- silvery-grey in colour
Many of these plants wait until it rains to flower. Rain also makes their seeds germinate and these seeds can stay dormant for a long time in the soil.Interesting facts
The giant saguaro cactus is:
- The tallest cactus in the world, growing up to 20m (67ft) high.
- It can weigh up to six tonnes, which is mainly the weight of the stored water.
- Some of these cacti are 250 years old.
- The Gila woodpecker nests inside the stem of the saguaro cactus where the temperature inside can be up to 30ºC (86ºF) cooler than outside.
The prickly pear cactus has a big network of shallow roots, which can quickly soak up lots of water when it rains.The ocotillo plant only grows leaves after it has rained - as soon as the soil dries out, they all drop off.
Some cacti spines are nearly 15cm (6in) long.
Boerhavia repens is a desert plant which can germinate, grow, produce flowers and ripen seeds in the space of ten days after it has rained.
The century plant takes 25 years to grow a flower. Then it dies. Lots of agaves do this!
Pebble plants (Lithops species) only have two leaves, and they look like the pebbles on the ground next to the plant. Their beautiful flower grows between the leaves.
Some species of agave plants (succulents not cacti) are also called Needle and Thread plants because the spiny tip and stringy leaf margin can be broken off and used to sew - and are even strong enough to sew through leather.
The spines of the Barrel cactus were used by local people for fishing hooks.