Herbicides

Definition of Herbicides

 Herbicides are pesticides used to kill unwanted plants

Selective herbicides kill specific targets, while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic mimics of natural plant hormones.

Herbicides used to clear waste ground, industrial sites, railways and railway embankments are not selective and kill all plant material with which they come into contact. Smaller quantities are used in forestry, pasture systems, and management of areas set aside as wildlife habitat.

Some plants produce natural herbicides, such as the genus Juglans (walnuts), or the tree of heaven; such action of natural herbicides, and other related chemical interactions, is called allelopathy.

Herbicides are widely used in agriculture and landscape turf management. In the US, they account for about 70% of all agricultural pesticide use

Zinnia

Zinnia is a genus of 20 species of annual and perennial plants of the family Asteraceae. They are native to scrub and dry grassland in an area stretching from the Southwestern United States to South America, with a centre of diversity in Mexico.^[3] Members of the genus are notable for their solitary long-stemmed flowers that come in a variety of bright colors. The genus name honours German botanist Johann Gottfried Zinn  Sun exposure: Full Sun Soil type: Any, Sandy, Loamy Flower color: Red, Pink, Orange, Yellow, Purple, White,Multicolor Bloom time: Summer Get a zing from zinnias! Zinnias are one of the easiest annuals to grow, grow quickly, and bloom heavily. They make a massive burst of color in your garden. Zinnias have bright, solitary, daisy-like flowerheads on a single, erect stem. The most common zinnia is "dahlia-flowered" and grows up to three feet. Other types are "cactus-flowered." Use in an annual or mixed border. Smaller zinnias are suitable for edging, windowboxes or other containers. The narrow-leaf zinnia also works well in hanging baskets. Zinnias are very popular for cut flowers. Planting Zinnias are grown from seed; they grow very quickly in the right conditions. Zinnias do not like to be transplanted. Full sun is essential wiht a minimum daylight temperature of 60 degrees F. Zinnias are adaptable but prefer fertile, humus-rich, well drained soil at pH preference 5.5 - 7.5. If soil is amended with compost, the flowers will grow more quickly. Sow seeds 1/4-inch deep. Space plants 4 to 24 inches apart depending on variety. (Many common varieties are 6 inches within the row and 2 feet in between rows.) See back of seed package. Germination occurs at 74 to 80 degrees F in 5 to 76 days. Sow in succession for a longer flowering display. Care Deadhead to prolong flowering. Maintain moderate soil moisture and fertilize lightly. Zinnias will die with the first frost. Pests Bacterial and fungal spots, powdery mildew, bacterial wilt. Minimize wetting of foliage to avoid disease. Caterpillars, mealybugs, and spider mites also cause problems. Avoid spraying and tolerate some leaf damage unless the situation is uncontrolled. Harvest/Storage Zinnias generally take 60 to 70 days from seed to flower (though it depends on conditions). Recommended Varieties Get a full-size flower on a compact plant with cultivars of the 'Dreamland Series.' Dwarf and compact, these zinnias have fully double flowerheads, to 4 inches across in a wide color range; stems are 8–12 inches tall. The 'Thumbelinia Series' cultivars and dwarf and spreading, with single or semi-double, weather-resistant flowerheads in many colors. Their petals are 1-1/4 inch across and stems grow up to 6 inches long. The 'State Fair Series' are the biggest and tallest of them all with large, double flowerheads that are 3 inches across. Stems grow to 30 inches tall. Special Features Attracts Butterflies Wit & Wisdom The small narrow-leaf zinnias make nice dried flowers, too.

Uses

A number of species of zinnia are popular flowering plants. Their varied habits allow for uses in several parts of a garden, and their tendency to attract butterflies and hummingbirds is seen as desirable.

Flower Structure

Structure of the Flower The floral meristem differentiates into four concentric groups of cells that form the four parts of the flower. The cells in whorl 1 develop into a whorl of sepals. These form at the lowest level. Collectively they make up the calyx. Whorl 2 forms above the calyx, forming the petals. Collectively these make up the corolla of the flower (the part that most ornamentals are grown for). Whorl 3 develops into the stamens, the male reproductive organs. The innermost whorl, 4, forms carpels, the female reproductive organs. Carpels often fuse to form a single structure, which some botanists call the pistil. What triggers the various parts of the floral meristem to enter one or another of these four developmental pathways?

Almonds flowers introduction

Almonds have been found in the ancient Greek tombs dating back to 8000 BC. In a society where philosophy was so important, the almond fruit came to symbolise knowledge, the ‘secret’ meaning hidden within, that has to be ‘cracked’ from its shell. The known and unknown world present in the almond’s form. Hence the term ‘kernel’s of wisdom’. The Romans showered newlyweds with almonds as a fertility charm. Almond trees are self-infertile and require cross fertilisation, for this reason the honeybees are essential to almond trees often colonising the trees themselves. Due to its early flowering the almond tree came to herald the arrival of spring, symbolising birth and resurrection.

Almond Blossoms is a group of several paintings made in 1888 and 1890 by Vincent van Gogh in Arles and Saint-Rémy, southern France of blossoming almond trees. Flowering trees were special to Van Gogh. They represented awakening and hope. He enjoyed them aesthetically and found joy in painting flowering trees. The works reflect Impressionist, Divisionist and Japanese woodcut influences. Almond Blossoms was made to celebrate the birth of his nephew and namesake, son of his brother Theo and sister-in-law Jo.

More information about "Almond Blossom"

Composition

Already in Arles, Van Gogh had been fascinated by the orchards, filled with apricot, peach and plum trees and in full bloom at the time of his arrival in March 1888. The composition of Almond Blossom is, however, both unusual and unique in Vincent’s oeuvre. The branches seem to float against the blue sky, and it is unclear if they are still part of the tree or set in a vase, as in one of his earlier works. With an unusual regularity, the entire pictorial surface has been filled with branches, which are further accented by the use of dark contours. Both this sharp outlining and the placement of the tree were certainly inspired by Japanese prints, which Van Gogh had seen for the first time in Paris. This influence can also be seen in a number of other paintings.

flowers photo period

Photoperiod
Photoperiod is detected in the leaves. The cocklebur, drawn here, needs at least 8.5 hours of darkness in order to flower. Even if only a part of one leaf is exposed to the correct photoperiod, the entire plant will bloom (middle figure). The leaves produce a chemical signal — called florigen — that is transmitted to the apical meristems to start their conversion into floral meristems. The right-hand drawing shows that grafting a cocklebur (B) that receives the required period of darkness to one (A) that does not causes flowering in both. Evidently the florigen signal passes from B to A through their connected vascular systems. Link to a discussion of photoperiodism. The chemical nature of florigen has been sought for decades. The most recent evidence suggests that at least one component is the protein encoded by the gene FLOWERING LOCUS T (FT).

signle flower

The Signal to Flower Flowering involves the conversion of the apical meristem into a floral meristem, from which all the parts of the flower will be produced. Signals that change the fate of the apical meristem include: maturity of the plant; temperature; the arrival of the plant hormone gibberellin; and, for many plants, photoperiod — the relative length of day and night.

flowering stages of sunflowers

Stage 1) Cut at this stage in the field to decrease petal damage. This is the first stage of the Sunflower, which we call "Tight." - When received at this cut stage the most important action is to re-cut the Sunflower and put the flower in a vase/bucket that has at least 5 inches of fresh water. - Takes approx. 2-3 days to go from Stage 1 to Stage 2. Stage 2) This is the second stage of the Sunflower cut which we refer to as the "Opening Stage." Be prepared to have stems within the bunch open inconsistently. - When received at this cut stage the most important action is to make sure the vase/bucket has fresh water (must be changed every 2 days) and is maintained at a consistent temperature (between 55º - 70º F). Stage 3) Ideal Stage for Sunflowers as they should have a more uniform cup-stage appearance. This third stage is known as the "Blooming Stage." - Make sure water has been replaced from initial uptake (Stage 2) and re-cut to accelerate opening stage. - Takes approx. 5-7 days to go from Stage 3 to Stage 4. Stage 4) This is the fourth and final stage of the Sunflower and is subsequently named the "Open Stage." Once it reaches the full blown state, petals will begin to fall off. - When Sunflowers reach this stage, they should be kept in low to moderate temperature (55º - 70º F), so they last longer and age less quickly. - Takes approx. 2-3 days before petals start falling off.

Pollination without insects

It's not always insects that pollinate the flowers; plants may use the wind, birds or even bats as pollinators! With wind-pollinated plants - such as grasses, cereals and some trees - the flowers are very simple, with no bright colours or nice smells as they don't need to attract the insects. These plants have both male and female reproductive parts and they make a lot of pollen. This is why a pollen allergy is called 'hay fever'.

Pollination by insects

An insect can pollinate flowers accidentally when the pollen is rubbed off the body of the insect. Plants can produce nectar within flowers, a sugary liquid, which many insects feed on. Pollen is a useful source of protein for some insects, such as bees. Insects are attracted to the flower by scent, colours and nectar. They carry pollen from flower to flower, while collecting nectar and pollen for themselves. After pollination, the plant produces a seed, which mostly grows protected inside the plants' ovaries.

What is pollination?

Pollination takes place when pollen lands on the stigma of a plant. It then travels down to the ovary and it's here that the ovules are fertilised. Most plants have flowers with the male and female parts present in each flower. Mostly, plants rely on insects, such as bees, to take the pollen from the anthers to the stigma.

Why Computer Science?

Why Computer Science?

 

 In 1943, Thomas J. Watson, Chairman of IBM declared: “I think there is a world market for maybe five computers.” A few billion computers later, there is a temptation to fall into Watson’s embarrassing underestimation of the potential that computing may have on our society. Indeed, in a few decades, “one computer per capita” may sound as outrageous as a “world market of five computers” sounds today. Computer scientists envision a world in which computing is pervasive and seamless. The golden age of computing (and of computer scientists) has barely begun. Students choose to major in computer science for a variety of reasons. Many of our students graduate to rewarding computer-related careers in software engineering, system administration and management, research and development in industrial and governmental laboratories. And, since computer technology has transformed almost all disciplines, many of our graduates use their computer science major (and the analytical skills it instills) to prepare them for a career in other disciplines such as medicine, law, education, physical and life sciences, social sciences, and humanities. Demand for graduates well-versed in computer science is high and is expected to continue to grow as the information age comes of age!

What Computer Science Is Not

What Computer Science Is Not…

 

 Computer Science is not just about building computers or writing computer programs! Computer Science is no more about building computers and developing software than astronomy is about building telescopes, biology is about building microscopes, and music is about building musical instruments! Computer science is not about the tools we use to carry out computation. It is about how we use such tools, and what we find out when we do. The solution of many computer science problems may not even require the use of computers—just pencil and paper. As a matter of fact, problems in computer science have been tackled decades before computers were even built. That said, the design and implementation of computing system hardware and software is replete with formidable challenges and fundamental problems that keep computer scientists busy. Computer Science is about building computers and writing computer programs, and much much more!

Computer Science

What is Computer Science?

 Computer Science is the systematic study of the feasibility, structure, expression, and mechanization of the methodical processes (or algorithms) that underlie the acquisition, representation, processing, storage, communication of, and access to information, whether such information is encoded in bits and bytes in a computer memory or transcribed in genes and protein structures in a human cell. The fundamental question underlying all of computing is: what computational processes can be efficiently automated and implemented? To tackle this seemingly simple question, computer scientists work in many complementary areas. They study the very nature of computing to determine which problems are (or are not) computable. They compare various algorithms to determine if they provide a correct and efficient solution to a concrete problem. They design programming languages to enable the specification and expression of such algorithms. They design, evaluate, and build computer systems that can efficiently execute such specifications. And, they apply such algorithms to important application domains.