Art review: Jenny Holzer: Blue Purple Tilt

• Jenny Holzer: Blue Purple Tilt

TEXT bombards you as soon as you arrive at the Talbot Rice Gallery, flyposted to the walls beside the lift. "Rejoice! Our times are intolerable," begins one writer, banging on about the blossoming apocalypse. Another's subject is vengeance, a third torture. These are Jenny Holzer's Inflammatory Essays, made in 1979-82, a collection of texts inspired by theorists, essayists and crackpots, each neatly and democratically represented in exactly 100 words.

Text is the stuff of Holzer's art. Many years before anybody had thought of Twitter, she was printing out quirky aphorisms, fly-posting them to phone boxes, printing them on T-shirts, letting them appear anonymously on the streets of New York. As she became fted as one of America's better-known contemporary artists, the technology became more sophisticated: large-scale projections and running columns of LEDs. Instead of the phoneboxes of Lower Manhattan, her words were in Times Square.

This is Holzer's first solo show in Scotland, part of the ongoing Artist Rooms project drawn from the collection of former gallerist Anthony d'Offay which is now owned jointly by the Tate and the National Galleries of Scotland. It also coincides with a major survey show of Holzer's work at the Baltic, Gateshead.

Technology has enabled Holzer to explore ever more sophisticated ways of showing text works. In Blue Purple Tilt, sentences cascade in vertical columns, a hypnotic waterfall of words, reflections and aphorisms, almost too fast to assimilate: "A little knowledge goes a long way"; "Anything is a legitimate area of investigation"; "Expiring for love is beautiful but stupid".

Certainly, the cascading forms set up an intriguing dialogue with their surroundings – in the half-dark of the Georgian Gallery, the racing LEDs echo the vertical columns of the room. But the overall effect of so much text is counter-productive, like Holzer's alphabetical listing of hundreds of truisms in the gallery nearby. While a single statement can be punchy, puzzling or provocative, even if it isn't all that strong – both Douglas Gordon and Martin Creed have used this to good effect – an endless catalogue of them soon starts to look mundane.

In the past decade Holzer has stopped writing her own texts, instead basing her works around declassified military documents relating to the wars in Iraq and Afghanistan released under the Freedom of Information Act. The main gallery space at Talbot Rice is occupied by six of these, reproduced as large paintings in colours which are meant to suggest bruising on human skin.

These are large-scale replications of maps and diagrams used in planning the American assault on Iraq. Air strikes float above Baghdad. Clear, businesslike text speaks of "Decisive offensive operations", targets are listed with (no irony here) bullet points: "Destroy/degrade Iraqi WMD delivery and production capability", "Destroy Iraqi forces". Numbers show personnel and tanks deployed; memoranda urge "Seize key terrain – Southern oilfields".

They manage to be at once shocking and mundane. By reproducing them on a monumental scale, she illustrates the fact that military orders start out as a memo on someone's desk and end up as another piece of filing, with unimaginable horrors contained between the two. This is war as paperwork.

Upstairs she dwells on censored documents, turning great blacked-out areas of text into monochrome abstracts so they look almost like works by Malevich or Robert Ryman. Yet these are not abstracts. There is always a visual clue – a heading, or perhaps a paragraph number – which reminds us what they are: texts which are hidden from view.

For an artist who works with text, whose focus is on content and communication, hidden text is a problem. In these works, she is denying herself her most powerful tool: words. The issues contained here can't be considered, debated or argued about because we can't read them. It is as if the solid panels of paint express her frustration. The great strength of Holzer's work is in its clarity, its willingness to engage, to be political and get angry when so much of contemporary art shrinks away from argument or opinion. But is also shows the limits of such direct work. War is a bad thing. Many things are hidden from us that should be revealed. After we have agreed with these statements, where is left for the work to take us? It is art as journalism, incisive and necessary but lacking in lasting resonance.

This makes Victoria Morton's work a kind of polar opposite. Her current show at Inverleith House is her largest to date and her first solo show in Scotland for eight years. It's careful and substantial, and high on resonance but low on clarity.

Glasgow-trained Morton uses the term "explicit abstract realism" to describe her work. She is best known for her abstract paintings, a kind of soft focus abstraction which suggests that it might have been connected to an image once, but is all the more tantalising for not giving you any clues about what that might be. And no, the titles don't help either.

More recently she has started to make three-dimensional works by incorporating found objects and painting on to items such as hinged wooden panels that are free-standing. In the well-proportioned Georgian rooms of Inverleith House, she creates a domestic flavour: paintings sit on ordinary-looking chairs or rest on top of wire-mesh bins. Occasional photographs are domestic in tone: balconies and washing lines in Italy; a scatter of dishes on a table; a rumpled bed. There are echoes here of Cathy Wilkes, a contemporary of Morton's, an exploration of the female perspective through suggestions of presence: a discarded dress, a pile of hairpins on the floor.

Yet Morton is first and foremost a painter. She has an instinctive confidence with colour, whether vibrant and clashing or delicate and sensitive, and a range of techniques from dense opaque daubing to saturated washes. Some works look highly controlled, others tactile and spontaneous, as if she was working the paint with her bare hands. In at least two places, she punctures the canvas violently.

There are some impressive large abstracts here. Soft Eaters, Hard Eaters is a dazzling explosion in a bead box, in contrast to Wah-Wah, which hangs opposite it and is an exercise in restraint. You Go No You Go is a beautiful thing, saturated colours seeping into one another and creating mysterious depths, which can be enjoyed simply for itself.

This is just as well, because Morton isn't throwing us many lifelines by which to understand these works. They are part of her own personal dialogue with the world and we must accept that – unlike Jenny Holzer, who readily invites us to share in her direct, angry, ironic engagement. Taken together, perhaps the two shows illustrate that neither approach is ideal. To combine resonance and clarity may be a greater challenge.

&149 Jenny Holzer to 15 May; Victoria Morton to 2 May

Art review: Jenny Holzer: Blue Purple Tilt | Victoria Morton