45

There are at least two separate answers to your question. First, with respect to plants needing CO2, they have evolved to deal with the limited amounts of CO2 normally in the atmosphere. That's really all they need, or "want": adding more doesn't really benefit them. Think of it this way: you need water to live, right? And drink a certain amount of it ...


43

That molecule is called Geosmin. It is mainly produced 1 by Actinomycetes such as Streptomyces which are filamentous bacteria that live in soil. Other organisms also produce geosmin: Cyanobacteria Certain fungi An amoeba called Vanella A liverwort It is an intracellular metabolite and cell damage is the primary reason attributed to its release. However ...


40

Nice question! Many vegetables taste bitter because they contain compounds known as phytonutrients (Greek phyto = "plant"). There are more than 2500 phytonutrients known, and the most important (and common) ones are categorized as1: Carotenoids: they are the ones that give red/orange/yellow color to some vegetables. They are mainly antioxidants, but some of ...


38

There are 5 answers, all "yes" (though the first one is disputable). First: there exists at least one animal which can produce its own chlorophyll: A green sea slug appears to be part animal, part plant. It's the first critter discovered to produce the plant pigment chlorophyll. The sea slugs live in salt marshes in New England and Canada. In ...


36

Exhaust gasses from combustion contain many compounds in addition to CO2. Some of them under the right circumstances‡ can be of limited benefit to some plants, but others such as ozone are damaging to all forms of life. Other compounds in vehicle exhaust that are known to cause damage to plants are oxides of sulfur and nitrogen — these react with water to ...


20

There are some other good answers which provide part of the picture, but I think there is a fundamental organising principle which has been missed. Konrad has touched on it in his answer. The reason trees, and most plants, tend to grow equally in all directions is that they have iteratively generated branching and radial symmetry which is controlled in a ...


19

It's not a single grass cell, but this does indeed appear to be a micrograph of a leaf of grass—so it actually contains numerous cells. Here's another image I was able to find with a much more clear description of exactly what you're seeing: Marram grass leaf. Light micrograph of a cross section through a closed (unravelled) leaf of Marram ...


18

Of course they can and do, except in total darkness (spectroscopically, only bands in the far red and in the blue spectra matter - blanking these affects 'total darkness'). In photosynhesis a photon is adsorbed by Photosystem II to break down water into oxygen and protons in solution. Another photon must be adsorbed by Photosystem ! to power the enzymatic ...


18

The big difference is that in humans, there is no mitosis in the haploid phase. There are three terms that are important here: Haplontic: Most of the life is spent in the haploid phase Diplontic: Most of the life is spent in the diploid phase Haplodiplontic (aka. diplohaplontic): About as much time is spent in the haploid phase than in the diploid phase ...


17

Yes, plants of all sizes can have cancerous growths. Agrobacterium tumifaciens, the causative agent of crown gall disease, produces what is called a tumor. See this link for detailed information on these growths. Alternatively, use a plant physiology textbook to look up the above terms. (Here, is where a textbook is better than a single abstract in PubMed.) ...


16

Bitter taste is sensed by bitter sensitive gustducin receptors (T2R family). There are different types of bitter receptors and they can be triggered by different kinds of ligands. Different classses of phytochemicals that can trigger bitter taste, are reviewed by Drewnowski and Gomez-Carneros (2000). The bitter tasting phytochemicals include phenols, ...


14

Ventricaria ventricosa (previously called Valonia ventricosa) is not exactly a single cell. It has a coenocytic structure with multiple nuclei and chloroplasts. As Jasand Pruski correctly guessed the organism possesses a large central vacuole which is multilobular in structure (lobules radiating from a central spheroid region). The entire cell contains ...


14

Short Answer: Any plant can produce oxygen at night, but plants cannot produce oxygen without light. Longer Answer: It all comes down to spontaneity of a reaction i.e. whether a reaction can occur without input of energy or not. Before we talk about spontaneity, I feel it better to first know about the process we're talking about here. In photosynthesis, ...


14

Firstly, I don't think it's entirely clear whether the entire premise of the question is correct. I couldn't find any evidence to suggest that plants don't thrive on highways and areas with lots of cars. If anyone has any data on this, I'd be interested in reading it. Some of the answers here seem to be a bit light on evidence. Let's look at some data on ...


13

It looks to me (although I'd want to use a microscope to check) like the black dots are xylem. When you cut the fruit, you've severed the xylem and also exposed the flat surface. Three main things have then happened: The increased surface area has led to the 'fleshy' part of the fruit contracting as the cells dehydrate. The stiffer, lignified xylem tubes ...


13

This is a transverse section (T.S.) of leaf blade a sort of Xerophytic (Desert-climate) grasses. such as Ammophila arenaria , Spartina sp, Agropyron sp, Poa pratensis etc. However similar-type-adaptation also seen in other (not-grass) plants. It is T.S. of an object like this. (highly diagrammatic, actually it is much more thinner, needle-like). The 2 sides ...


13

It is protection against rapid warming of the cambium layer. A lot of far northern timber has light colored bark which reflects sunlight. The rapid heating from very cold after sunrise can actually damage or even split the bark of dark colored species. This is called sunscalding.


13

Evolutionary answer: I like to go one step before green plants and consider the humble alga. Algae were historically classified as green, red, and brown, based on the wavelengths that their characteristic pigments absorbed. It is believed that land plants evolved from a common ancestor of algae, so you might wonder why we don't have similar broad categories ...


12

Animals and plants are both classified as Eukaryotes, and as such can form large, complex, multi-cellular organisms. There are several major differences at the cellular level that distinguish the 2 Kingdoms (Animalia and Plantae). Without getting technical, the most crucial difference in relation to your question is that plants contain chlorophyll, and as ...


12

In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as ...


12

Disclaimer: This is not my field of research. First, this is not a complete answer to our question. A nice explanation of the current hypothesis of water transport in trees (Dixon-Joly cohesion-tension theory, originally proposed 1894) can be found at The Amazing Physics of Water in Trees but also in Tyree (1997). The key points are that the stoma (leaf ...


12

tl;dr: Sort of? Logically, either red or blue light should be sufficient. Chlorophyll a and chlorophyll b preferentially activate different photosystems, and both photosystems are required in green plants. Practically, we're in luck and someone has actually done the experiment. As the original study reports, plants need a little blue light to grow into ...


12

Back in the early days of climate science, there were some scientists who considered the possibility that increased CO2 production would lead to increased plant growth, and that this in turn would result in keeping the oxygen-carbon dioxide balance more or less stable. This was referred to as the "Gaia hypothesis" and basically revolved around viewing the ...


11

This is an interesting topic! Crassulacean acid metabolism is a second CO₂ fixation pathway where CO₂ is absorbed at night. The CO₂ is fixed into maleic acid HOOC-CH₂CH(OH)-COOH which stores some of the CO₂ in the form of carboxyl groups. During the day carboxylases release the CO₂ for fixation during the day. This is an adaptation where the stomata ...


11

In my experience (in common with the experience of everyone I've talked to who could be considered an expert on the subject), taking old wood and using that as a scion when grafting new trees rejuvenates them, and they grow as new trees. I'll take apple trees as an example. As you can see from the table here, there is a distinct age after which the tree ...


11

First of all, you assumption seems to be incorrect. Plants in same part of the world can twine in opposite directions. Little seems to be known exactly. Gravity has nothing to do with plant's chirality (or "handedness") or spiraling: How plants do this is still unknown. Darwin proposed that it was "autonomously induced." This came to be known as the ...


11

There are three types of endosperms encountered in botany - nuclear, heliobial and cellular. The endosperm of Cocos nucifera is both special and interesting. Initially, the cocunut is a nuclear liquid endosperm. Meaning, it is a coenocytic liquid tissue with lots of rapidly dividing nuclei. The reference I cite here (although pretty old), states that it is ...


11

The two commonly put-forward explanations for spiral growth of tree trunks related to stress-loading and damage-tolerance. The stress-loading explanation states that spiral-grained trees flex more than straight-grained trees before they break. Flexibility under stress-loading is useful in areas with heavy snowfall (as the tree can flex until the snow falls ...


10

They are basically conjoined apples which share a common stalk. They are rare but do happen. Here is an article of one discovered in a backyard. conjoined apple discovered in a store (reference) It apparently happens because of bad weather conditions, stress and insect damage. Fused fruits are also found in the case of cherries, watermelons, peaches etc. ...


10

The authors of this 2012 review article summarize the problem well in their introduction: In contrast to the tremendous advances in throughput, assembling sequencing reads remains a substantial endeavor, much greater than the sequencing efforts alone would suggest [22-24]. Large complex plant genomes remain a particularly difficult challenge for de novo ...


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