Requirements for photosynthesis

What Limits Plant Respirati0n

In order that a plant may build up organic compounds such as sugars, it must have a supply of carbon which is readily available. Carbon dioxide is present in the air in concentrations of 330 ppm parts per million or 0.03 per cent, and can diffuse into the leaf through the stomata. Carbon dioxide gas moves ten thousand times faster in air than it would in solution through the roots. The amount of carbon dioxide in the air immediately surrounding the plant can fall when planting is very dense, or...

Nutrient film technique NFT

Manual Hydroponics

This is a method of growing plants in a shallow stream of nutrient solution continuously circulated along plastic troughs or gullies. The method is commercially possible because of the development of relatively cheap non-phytotoxic plastics to form the troughs, pipes and tanks see Figure 22.5 . There is no solid rooting medium and a mat of roots develops in the nutrient solution and in the moist atmosphere above it. Nutrient solution is lifted by a pump to feed the gullies directly or via a...

Peachpotato aphid Myzus persicae

Myzus Persicae

This and similar species are often referred to by the name 'greenfly' Figure 14.8 . Damage. It is common in market gardens and greenhouses. The nymph and adult of this aphid may cause three types of damage. Using its sucking stylet, it may inject a digestive juice into the plant phloem, which in young organs may cause severe distortion. Having sucked up sugary phloem contents, the aphid excretes a sticky substance called honey-dew, which may block up leaf stomata and reduce photosynthesis,...

Stages Of Soil Formation

Sedentary Soil

Erosion is the movement of rock fragments and soil. Erosion is the movement of rock fragments and soil. Figure 17.3 Rocks. Granite pink left silver top sandstone right slate bottom Figure 17.3 Rocks. Granite pink left silver top sandstone right slate bottom Igneous rocks are those formed from the molten material of the Earth's crust. All other rock types, as well as soil, are ultimately derived from them. When examined closely, most igneous rocks can be seen to be a mixture of crystals. Granite...

Artificial control offlowering

Black Out Curtains For Greenhouse

A long night may be broken artificially using a technique called night-break lighting. Incandescent tungsten bulbs produce a high proportion of red light and are cheap to run. Hung about 1 m above the crop and spaced to give about 150 lux for four hours ensures that the Pfr730 critical level is not reached. Cyclic lighting saves electricity and uses a series of brief alternating light and dark cycles to replace one continuous break. High pressure sodium lamps are used where they are installed...