Once fertilization has taken place, the energies of the plant are directed to the successful development of the next generation. The fertilized egg cells are safely protected from the vagaries of climate, or damage by passing insects, by the surrounding mass of the ovary which lies at the base of the now fading flower.

Each part of the ovary has its own role to play in the growth and development of the new seed. Despite a few basic differences, the pattern followed by the growing embryo is characteristic of all plants. At fertilization the egg is made up of a single cell, but this soon begins its growth by dividing into two identical cells. Read the rest of this entry »

Trees which do not shed layers of dead tissues regularly have increasingly rugged bark as they age. This can often be observed by noting the relatively smooth nature of the top of a trunk in comparison with the older parts at the bottom. With age, the pressure from within causes the surface to crack and the resulting deep fissures are typical of many trees. The way trees develop such features can be diagnostic and one of the most distinctive is the Sweet Chestnut (Caslanea saliva) which usually cracks in spirals. Read the rest of this entry »

To examine the rings of a tree without felling it, cores can be taken by boring into the wood with a hollow cylinder. By counting them inwards each ring can be accurately dated, the age of the tree can be determined and past climatic conditions can be inferred. For accuracy a number of trees is sampled and the ring widths compared. If they coincide, as they normally do, then narrow rings will indicate a poor growing season, probably one with a spring and early summer drought, Read the rest of this entry »

Generally, however, the vascular bundles in a straight piece of grass stem — Maize (Zea mays) being a good example — do not run parallel to the sides but weave from the inner part of the stem to the outer, returning inwards after the leaf traces have branched off. So the vascular tissue forms a series of spirals through the stem. As well as having a different arrangement in the stem, these vascular bundles are different in their individual make-up, there being no layer of cambium between the xylem and the phloem. This means that they cannot develop a woody, strengthening tissue as can dicotyledonous plants. There are exceptions, however, as in the palms and allied woody-stemmed monocotyledons. Read the rest of this entry »

How remarkable it is that the single cell that begins the life of a plant can develop in such an immense variety of ways. Looking at k a newly fertilized cell within an ovary, it is not possible to tell whether it will develop into a tiny alpine plant only a few centimetres high or a giant Californian Redwood (Sequoia sempervirens) over 100 metres tall. The beginnings are the same, but as that one cell grows and divides so the characteristics of the new plant emerge. If it is to be an annual and complete its life-cycle within a year, then there is no need for elaboration of stem cells to give strength and durability. Read the rest of this entry »

How long does a plant live? Can environmental conditions such as soil and climate have any influence and how much can individual plants deviate from the normal pattern? All these are questions which are often asked. The first is the most difficult to answer, and to do so with any sense it is necessary to look at the three broad groups into which higher plants are divided. These are annuals, biennials and perennials. Read the rest of this entry »